RU2805753C2 - Device and method of catalysis - Google Patents

Abstract

FIELD: catalysing electrochemical redox reaction.

SUBSTANCE: invention relates to a method for catalysing an electrochemical redox reaction of active particles in a conducting solution. The method includes: providing an electrocatalytic matrix containing a supporting substrate; surface structures protruding from the support substrate, the surface structures comprising an electrocatalyst; a functional surface on the electrocatalyst, wherein the functional surface is located in the upper part of the surface structures and wherein the functional surface is intended for contact with active particles in the conductive solution; immersing surface structures in the solution and introducing a counter electrode into it; and generating a current or voltage between the electrocatalyst and the counter electrode such that the charge density, voltage or current, is focused on the functional surfaces and the active particles undergo an oxidation-reduction reaction upon contact with the functional surfaces. In this case, the plurality of surface structures has a uniform size and edges and/or vertices that contain the catalyst, the catalyst is applied to the top surface of the surface structures and is a material different from the surface structure, the electrocatalyst is applied to the vertices of the surface structure, the electrocatalyst is applied to less than about 50% to approximately 0.000001% of the matrix surface when viewed from above.

EFFECT: invention provides an alternative method for catalysing an electrochemical redox reaction.

27 cl, 19 ex, 25 dwg

Description

Field of technology to which the invention relates

The invention relates to a method for catalyzing an electrochemical redox reaction. More specifically, the invention relates to a method for catalyzing an electrochemical redox reaction using an electrocatalyst with surface structure(s) that can reduce the costs associated with the use of expensive catalyst materials.

State of the art

Heterogeneous catalysis is used in a number of important redox catalytic processes, including _H2 production for energy storage and _O2 reduction in fuel cells. However, catalysts are often expensive materials. For a given electrocatalytic reaction, it is desirable that the catalytic reaction proceed at potentials as close as possible to the potential of the non-polarizable electrode (thermodynamic electrode potential) with a satisfactory reaction rate. However, as a rule, improving one aspect of the catalytic process has a negative effect on another, for example, increasing the reaction rate often requires a larger driving force and, as a result, a large deviation from the thermodynamic potential.

Several parameters are considered when optimizing a catalytic process, including: catalytic material, solvent used (e.g., aqueous, organic solvent), solution characteristics (e.g., pH, viscosity, and electrolyte), fluidity versus static, cell design, material shape, and electrode orientation . The main component is the electrode, which includes a catalyst either on the surface or in the body of the electrode matrix. Alternatively, in the case of a metal, the electrode material may also be a catalytic material.

The catalyst optimization process typically involves optimizing each of the above parameters in terms of impact on the kinetic and thermodynamic response within the system and provides an understanding of how each variable affects catalytic efficiency in terms of rate and energy required. However, until now very little attention has been paid to the influence of electrode surface topography on catalytic efficiency.

The objective of the invention is to create a method for catalyzing the electrochemical redox reaction of active particles in a conducting solution. The objective of the invention is to reduce the cost of catalysis of the electrochemical redox reaction of active particles in a conducting solution. Alternatively, the object of the invention is to at least provide choice to the public.

The essence of the invention

According to a first aspect of the invention, there is provided a method for catalyzing an electrochemical redox reaction of active species in a conductive solution, comprising the following steps:

the presence of an electrocatalytic matrix containing:

supporting substrate;

surface structures protruding from the support substrate, the surface structures including an electrocatalyst;

a functional surface on the electrocatalyst, wherein the functional surface is located in the upper part of the surface structures and wherein the functional surface is intended for contact with active particles in the conductive solution;

b. immersing surface structures in the solution and introducing a counter electrode into it; And

c. creating a current or voltage between the electrocatalyst and the counter electrode such that the charge density (voltage or current) is focused on the functional surfaces and the active species undergo a redox reaction upon contact with the functional surfaces.

In some embodiments of the invention, the redox reaction is selected from one or more of the following types: evolution of hydrogen from water,

release of oxygen from water,

release of hydrogen from water,

release of hydrogen from protons,

oxidation of hydrogen to water,

oxidation of hydrogen to protons,

oxidation of hydrogen to hydrogen peroxide,

reduction of oxygen to water,

reduction of oxygen to hydrogen peroxide,

carbon dioxide to carbon monoxide,

carbon dioxide to methanol,

carbon dioxide to carboxylic acid (for example formic acid),

carbon dioxide to aldehyde and/or ketone,

carbon dioxide to methane, ethane, propane and/or higher order carbon chains up to _C21 ,

oxidation of methane to methanol,

nitrogen to hydrazine,

nitrogen to ammonia,

splitting ammonia into hydrogen and nitrogen,

methane to methanol

nitrate to nitrogen

nitrate to ammonia.

In some embodiments, the redox reaction is a combination of redox reactions. For example, the release of hydrogen and oxygen from water, followed by the reduction of oxygen back to water; the separation of hydrogen from water, followed by the combination of hydrogen with nitrogen to form ammonia.

In some embodiments, the redox reaction involves a series of steps, preferably not releasing an intermediate. For example, carbon dioxide is converted to carbon monoxide, then carbon monoxide is converted to methanol, but no carbon monoxide is released.

In some embodiments, the redox reaction is a process with 2 or more electrons. In some embodiments, the redox reaction is a 2-electron process. In some embodiments of the invention, the 2 electron process is selected from the following:

release of hydrogen from water

release of hydrogen from protons

oxidation of hydrogen to hydrogen peroxide

reduction of oxygen to hydrogen peroxide

carbon dioxide to carbon monoxide

carbon dioxide to formic acid

methane to methanol.

In some embodiments, the redox reaction is a process with 4 or more electrons. In some embodiments, the redox reaction is a 4-electron process. In some embodiments of the invention, the 4 electron process is selected from the following:

release of oxygen from water

reduction of oxygen to water

nitrogen to hydrazine

carbon dioxide to formaldehyde

oxidation of hydrogen to water.

In some embodiments, the redox reaction is a process with 6 or more electrons. In some embodiments, the 6 electron process is selected from the following:

carbon dioxide to methanol,

nitrogen to ammonia,

splitting ammonia into hydrogen and nitrogen.

In some embodiments, the redox reaction is a process with 8 or more electrons. In some embodiments, the 8 or more electron process is selected from the following:

carbon dioxide to methane, ethane, propane and/or higher order carbon chains up to _C21 ;

carbon dioxide to acetic acid,

carbon dioxide to ketone,

nitrate to nitrogen,

nitrate to ammonia.

According to another aspect, there is provided a method of catalyzing an electrochemical redox reaction of active species in a conductive solution, comprising the following steps:

a. the presence of an electrocatalytic matrix containing:

i. supporting substrate;

ii. surface structures protruding from the support substrate, the surface structures including an electrocatalyst;

iii. a functional surface on the electrocatalyst, wherein the functional surface is located in the upper part of the surface structures and wherein the functional surface is intended for contact with active particles in the conductive solution;

b. immersing surface structures in the solution and introducing a counter electrode into it; And

c. creating a current or voltage between the electrocatalyst and the counter electrode such that the charge density (voltage or current) is focused on the functional surfaces and the active species undergo a redox reaction after contact with the functional surfaces,

where the active species is oxygen and the oxygen is reduced to water.

According to another aspect, there is provided a method of catalyzing an electrochemical redox reaction of active species in a conductive solution, comprising the following steps:

a. the presence of an electrocatalytic matrix containing:

i. supporting substrate;

ii. surface structures protruding from the support substrate, the surface structures including an electrocatalyst;

iii. a functional surface on the electrocatalyst, wherein the functional surface is located in the upper part of the surface structures and wherein the functional surface is intended for contact with active particles in the conductive solution;

b. immersing surface structures in the solution and introducing a counter electrode into it; And

c. creating a current or voltage between the electrocatalyst and the counter electrode such that the charge density (voltage or current) is focused on the functional surfaces and the active species undergo a redox reaction after contact with the functional surfaces,

where the active species are water or protons, and the water or protons are reduced to hydrogen.

According to another aspect, there is provided a method of catalyzing an electrochemical redox reaction of active species in a conductive solution, comprising the following steps:

a. the presence of an electrocatalytic matrix containing:

i. supporting substrate;

ii. surface structures protruding from the support substrate, the surface structures including an electrocatalyst;

iii. a functional surface on the electrocatalyst, wherein the functional surface is located in the upper part of the surface structures and wherein the functional surface is intended for contact with active particles in the conductive solution;

b. immersing surface structures in the solution and introducing a counter electrode into it; And

c. creating a current or voltage between the electrocatalyst and the counter electrode such that the charge density (voltage or current) is focused on the functional surfaces and the active species undergo a redox reaction after contact with the functional surfaces,

where the active species is nitrogen and the nitrogen is reduced to ammonia.

According to another aspect, there is provided a method of catalyzing an electrochemical redox reaction of active species in a conductive solution, comprising the following steps:

a. the presence of an electrocatalytic matrix containing:

i. supporting substrate;

ii. surface structures protruding from the support substrate, the surface structures including an electrocatalyst;

iii. a functional surface on the electrocatalyst, wherein the functional surface is located in the upper part of the surface structures and wherein the functional surface is intended for contact with active particles in the conductive solution;

b. immersing surface structures in the solution and introducing a counter electrode into it; And

c. creating a current or voltage between the electrocatalyst and the counter electrode such that the charge density (voltage or current) is focused on the functional surfaces and the active species undergo a redox reaction after contact with the functional surfaces,

where the active species is carbon dioxide and the carbon dioxide is reduced to methanol.

According to another aspect, there is provided a method for catalyzing a redox reaction of active species in a conductive solution, comprising the following steps:

impact on the electrocatalytic system of active particles; And

supplying voltage to the electrocatalytic system;

and:

the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species;

The electrocatalytic system includes:

counter electrode; And

electrocatalytic matrix containing:

supporting substrate;

surface structures of uniform size protruding from the surface of the supporting substrate; And

surface structures of uniform size, including ridges and peaks containing the catalyst.

In some embodiments, the edges and/or vertices comprise less than about 50% of the surface area, less than about 40%, less than about 30%, less than about 20%, less than about 10%, less than about 1%, less than about 0.01%, less than about 0.001%, less than about 0.0001%, less than about 0.00001%, less than about 0.000001%. In some embodiments, the fins and/or peaks comprise from about 0.0000001%, or from about 0.000001% to about 50% of the surface area of the catalyst as viewed from above. In some embodiments, the fin tips comprise from about 0.0001% to about 50% of the surface area of the catalyst when viewed from above. In some embodiments, the fin tips comprise from about 0.1% to about 50% of the surface area of the catalyst when viewed from above. In any of the embodiments of the present invention, surface structures with uniform size may also have uniform geometry.

With respect to surface structures, a plurality of surface structures of substantially uniform size and/or uniform geometry may be present, and the plurality of surface structures may contain a catalyst or catalytic material at one or more edges and/or apexes and/or tips and/or apexes of said structures.

In some embodiments, the multi-electron oxidation or multi-electron reduction of active species includes a 2-electron process, a 4-electron process, a 6-electron process, an 8-electron process, a 10-electron process, or a 12-electron process.

In some embodiments, multi-electron oxidation or multi-electron reduction of active species includes a 2-electron process including evolution of hydrogen from water or protons, oxidation of hydrogen to water or protons, oxidation of hydrogen to hydrogen peroxide, reduction of oxygen to hydrogen peroxide, conversion carbon dioxide to carbon monoxide or the reduction of nitrogen ( _N2 ) to hydrazine or methane to methanol.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species includes a 2-electron process involving the conversion of carbon dioxide to carbon monoxide.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the reactive species includes a 4-electron process involving the evolution of oxygen from water, the reduction of oxygen to water, the reduction of carbon dioxide to an aldehyde, or the reduction of carbon dioxide to formic acid.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species includes a 4-electron process involving the reduction of carbon dioxide to an aldehyde or the reduction of carbon dioxide to a carboxylic acid.

In some embodiments, multi-electron oxidation or multi-electron reduction of active species includes a 6-electron process involving the reduction of carbon dioxide to alcohol, the reduction of nitrogen (N ₂ ) to ammonia, or the production of hydrogen and nitrogen from ammonia. In some embodiments, the alcohol is methanol.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species includes a (2n+6)-electron process involving the reduction of carbon dioxide to an alkane of the formula _{CnH2n +2} , where n is from 2 to 21.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the reactive species involves an 8-electron process involving the conversion of nitrate anions to ammonia.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species includes a 10-electron process involving the oxidation of ethane.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species involves an 11-electron process involving the conversion of nitrate anions to nitrogen.

In some embodiments, the multi-electron oxidation or multi-electron reduction of the active species includes a 12-electron process involving the oxidation of propane.

According to another aspect, a method is provided for catalytically gassing active species in a conductive solution. Such methods include exposing the electrocatalytic system to active species and applying a voltage to the electrocatalytic system. With regard to such methods, the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species. In addition, the electrocatalytic system contains: a counter electrode; and an electrocatalytic matrix, wherein the electrocatalytic matrix includes a support substrate; surface structures of uniform size protruding from the surface of the supporting substrate; wherein the surface structures of uniform size have edges and/or vertices containing a catalyst; and the gas generation rate is increased by at least 1.5 times compared to the same electrocatalytic matrix without uniformly sized surface structures protruding from the surface of the supporting substrate. In any of the embodiments of the present invention, surface structures with uniform size may also have uniform geometry.

With respect to surface structures, a plurality of surface structures of substantially uniform size and/or uniform geometry may be present, and the plurality of surface structures may contain a catalyst or catalytic material at one or more edges and/or apexes and/or tips and/or apexes of said structures.

In another embodiment of the invention, the rate of gas formation is increased by a factor of up to 1000. In another embodiment of the invention, the rate of gas formation is increased by a factor of 1.5 to 1000, in another embodiment of the invention - from 10 to 1000, in another embodiment of the invention - from 20 to 1000. 500, in another embodiment of the invention - from 50 to 500, in another embodiment of the invention - from 50 to 300.

According to another aspect, a method is provided that allows the selection of an electrocatalytic matrix based on the desired product yield. The methods include exposing the electrocatalytic system to an active agent dissolved or suspended in a conductive solution; and applying voltage to the electrocatalytic system. As for such methods, the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of active species, and the electrocatalytic system includes a counter electrode; and electrocatalytic matrix. The electrocatalytic matrix includes a support substrate; and uniformly sized surface structures protruding from the surface of the support substrate, wherein the uniformly sized surface structures have ridges and/or apexes containing the catalyst. If the surface structures with a uniform size are on a micrometer scale, then a first product is obtained, however, if the surface structures with a uniform size are on a nanometer scale, a second product is obtained, the first and second products being different. To obtain the second product, a higher order electronic process is required compared to obtaining the first product. In other words, more electrons are required to produce the second product than to produce the first product. In any of the embodiments of the present invention, surface structures with uniform size may also have uniform geometry.

With respect to surface structures, a plurality of surface structures of substantially uniform size and/or uniform geometry may be present, and the plurality of surface structures may contain a catalyst or catalytic material at one or more edges and/or apexes and/or tips and/or apexes of said structures.

According to another aspect, a method is provided that allows the electrocatalytic matrix to be selected depending on the desired product yield; the method includes exposing an electrocatalytic system to an active agent dissolved or suspended in a conductive solution; And

supplying voltage to the electrocatalytic system,

and:

the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species;

The electrocatalytic system includes:

counter electrode; And

electrocatalytic matrix containing

supporting substrate;

surface structures of uniform size protruding from the surface of the supporting substrate; And

uniformly sized surface structures including ridges and/or peaks containing catalyst;

wherein if the uniformly sized surface structures are on a micrometer scale, a first product ratio is obtained, and if the uniformly sized surface structures are on a nanometer scale, a second product ratio is obtained, wherein the first and second product ratios are different;

obtaining the second product ratio requires a higher order electronic process than obtaining the first product ratio.

In some embodiments, the active component is oxygen, the first product may be hydrogen peroxide (2-electron process) (i.e., the resulting ratio of hydrogen peroxide to water is 100:0), and the second product may be water (4-electron process) process) (i.e. the resulting ratio of hydrogen peroxide to water is 0:100).

In some embodiments, the width of the nanometer-scale surface structures at the junction with the support substrate is from about 25 nm to about 50,000 nm.

In some embodiments, the width of the surface structures on a micrometer scale at the junction with the support substrate is from about 5 μm to about 500 μm.

In some embodiments, an inert or passivation layer may be provided between the surface structures to facilitate changes in product ratios.

In some embodiments, the inert or passivating or substantially less active layer may be positioned such that its thickness allows the relative product ratio between the second product ratio and the first product ratio to be adjusted.

In some embodiments, the greater the thickness or increased thickness of the inert or passivation layer, the closer the relative ratio becomes to the first product ratio.

In some embodiments of the invention, the relative ratio between the first product ratio and the second product ratio may be adjusted in accordance with the relative thickness or height of the inert or passivation layer (by adjusting the force on the surface structure, for example, with a smaller surface structure area or with a larger surface structure area ).

Regarding the thickness of the inert or passivation layer, the thickness is selected depending on the height of the surface structure above the load-bearing surface.

The above adjustment of the thickness of the inert or passivation layer can be applied to the production of a functional surface or catalyst.

In some embodiments, the thickness of the inert or passivation layer may be from about 5% to about 95% of the height of the surface structure.

In some embodiments, the thickness of the inert or passivation layer may be at least 99% of the height of the surface structure.

In some embodiments of the invention, the thickness of the inert or passivation layer may be a proportion of the height of the surface structure to expose the nanometer-sized apex or apexes of the surface structure.

For example, in some embodiments of methods where the active species is oxygen, the first product may be hydrogen peroxide (2-electron process) and the second product may be water (4-electron process).

In another embodiment of the methods where the active species is CO ₂ , the first product may be CO, the second product may be formic acid, and the third product may be methanol. In another embodiment of the methods where the active species is a nitrate, the first product may be ammonia and the second product may be nitrogen. In another embodiment of the methods where the active species is nitrogen, the first product may be hydrazine and the second product may be ammonia.

In another aspect, a method is provided for selecting an electrocatalytic matrix based on desired product yields. The methods include exposing an electrocatalytic system to an active agent dissolved or suspended in a conductive solution, applying a voltage to the electrocatalytic system, and collecting the redox reaction product. With regard to such methods, the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species. Also in the methods, the electrocatalytic system includes a counter electrode; and an electrocatalytic matrix, the matrix including a support substrate and uniformly sized surface structures protruding from a surface of the supporting substrate, wherein the uniformly sized surface structures have ridges and/or apexes containing the catalyst. Also in the methods, the sizes of uniformly sized surface structures are selected to vary the resulting redox reaction product.

In some such embodiments, the active agent is oxygen, the surface structures of uniform size are micrometer scale, and the product of the oxidation-reduction reaction is hydrogen peroxide. In other such embodiments, the active agent is oxygen, the uniform sized surface structures are on a nanometer scale, and the product of the redox reaction is water.

According to another aspect, a method for obtaining gas from an electrode is provided. The method includes exposing an electrode to a conductive solution containing active particles; and applying a voltage to the electrode sufficient to reduce or oxidize the active species to form a gas. In this method, the electrode contains a nanostructured matrix, which, in turn, includes a supporting substrate; and pyramidal surface structures protruding from the supporting substrate. In the array, each of the pyramidal surface structures has a base, an apex, and ridges between the base and the apex, the base being in contact with a supporting substrate, and the longest lateral dimension of the base being from 50 nm to about 4000 nm, the apex dimension being from about 1 nm to about 50 nm and the distance between adjacent vertices is from about 50 nm to 1000 nm; wherein the ribs and the top contain a catalyst.

In some embodiments, the method further includes an electrolytic system comprising an electrode and a counter electrode. In some embodiments, the apexes are designed such that gas formation begins at the apex. In any such embodiment, the gas may be hydrogen, oxygen, or both hydrogen and oxygen. In any such embodiment, the gas may be hydrogen, nitrogen, or both hydrogen and nitrogen. In any embodiment, the gas may be ammonia.

In some embodiments, the pyramidal surface structures in the nanostructured matrix are substantially the same shape and height.

According to another aspect, there is provided an electrocatalytic matrix comprising:

supporting substrate;

surface structures of uniform size protruding from the surface of the supporting substrate; And

evenly spaced surface structures of uniform size, including ridges and vertices; And

platinum and carbon deposited on at least a portion of the surface structures.

In another aspect, any one or more of the above aspects or the following embodiments of the invention as described herein can facilitate catalyst replacement with a catalyst of lower economic cost and/or labor intensity and/or reduced quantity.

In this case, the substituted catalyst has a lower reactivity and/or a smaller amount than the catalyst that it replaces or should replace.

For the avoidance of doubt, the following embodiments of the invention relate to all aspects described above.

In some embodiments of the invention, the cross-sectional area of the surface structure is reduced along an axis orthogonal to the top surface of the support substrate.

In some embodiments of the invention, the upper portion of the surface structure has a convex upper surface.

In some embodiments, the surface structure has a triangular, convex, semicircular, or papillary cross-section along a plane orthogonal to the top surface of the support substrate.

In some embodiments, the top of the surface structure has an angle of about 90° or less at the top. In some embodiments of the invention, the surface structure is a sharp end or ridge.

In some embodiments, the surface structures are pyramidal, conical, ridged, pointed, jagged, cylindrical, square pentagonal, flat top pentagonal, pentagonal or hexagonal, or combinations thereof. Any such structures may have edges, vertices, ridges, or any combination of two or more such features.

In some embodiments, the surface structure has a substantially triangular, substantially circular, or substantially square cross-section along a plane parallel to the top surface of the support substrate.

In some embodiments of the invention, the surface structures are uniformly distributed on the support substrate. Alternatively, the surface structures are arranged randomly on the support substrate.

In some embodiments of the invention, the surface structures are substantially uniform in size. It is believed that uniform size and/or geometry can provide substantially uniform results, such as, but not limited to, substantially uniform current and/or voltage across each structure, producing a substantially uniform product. In an exemplary embodiment of the invention, the surface structures and catalyst may be configured to produce primarily a predetermined primary or preferred product. Alternatively, the surface structures and catalyst may be configured to produce one or more predetermined products, for example, a preferred or primary product, and a secondary product (which may also be preferred). Likewise, the surface structures and catalyst can be configured to minimize the production of undesired product.

With respect to surface structures, a plurality of surface structures of substantially uniform size and/or uniform geometry may be present, and the plurality of surface structures may comprise a catalyst or catalytic material at one or more edges and/or apexes and/or tips and/or apexes of said structures.

In some embodiments of the invention, the surface structures have at least one line of symmetry. In some embodiments of the invention, the surface structures have at least two lines of symmetry.

In some embodiments of the invention, the surface structure (or structures) is/are characterized by one or more of the following:

i. identical or different or dissimilar heights from the surface of the supporting substrate,

ii. same or different or heterogeneous shape geometry in relation to other surface structure (or structures),

iii. correct or incorrect geometry,

iv. location at equal or unequal distances from each other,

v. same or different or heterogeneous density,

vi. a group of a plurality of said surface structures containing a plurality of surface structures according to any one of items i-v.

In some embodiments, the surface structure (or structures) is/are characterized by a predetermined spacing or density such that a number of vertices or ends act as a functional surface, or so that a functional surface of the required size and density is formed on them for reduction or oxidation of active species, such as described in this document.

In some embodiments of the invention, the surface structure (or structures) is/are characterized by a predetermined uniform spacing or density such that a number of vertices and/or ends of the same size act as a functional surface, or so that a functional surface of the required size and density is formed thereon to restore or oxidation of active species as described herein. In any of the embodiments of the present invention, surface structures with uniform size may also have uniform geometry.

With respect to surface structures, a plurality of surface structures of substantially uniform size and/or uniform geometry may be present, and the plurality of surface structures may comprise a catalyst or catalytic material at one or more edges and/or apexes and/or tips and/or apexes of said structures.

In some embodiments of the invention, the surface structure (or structures) contains/contain a distal end portion, wherein said distal end portion is furthest from the surface from which said surface structure (or structures) extends, wherein said distal end portion has a pointed shape, or the shape of a vertex, or peak, or tenon, or ridge that allows to act as a functional surface or allows a functional surface to be formed upon it.

In some embodiments of the invention, the surface structure (or structures) is/are presented as an array or multiple arrays of surface structures located on a support surface of the substrate.

In some embodiments, the matrix or each matrix is a geometrically ordered uniform pattern.

In some embodiments, the matrix or each matrix is a sequentially ordered pattern of grouping of surface structures.

In some embodiments, the matrix or each matrix is separately created by the molding tool of a continuous molding machine, hot stamping, lithography, injection molding, stamping, electroforming, lithography, or other molding technology.

In some embodiments, the width of the surface structure at the junction with the support substrate is from about 20 nm to about 5000 μm. In some embodiments, from about 40 nm to about 4000 microns; from about 55 nm to about 3000 μm; from about 75 nm to about 2500 μm; from about 100 nm to about 4000 μm; from about 250 nm to about 3500 μm, from about 20 nm to about 3500 μm; from about 2 nm to about 4000 μm; from about 20 nm to about 2500 μm; from about 20 nm to about 4000 μm; from about 20 nm to about 3000 μm; from about 20 nm to about 2000 µm. In some embodiments, from about 5 nm to about 750 microns; from about 5 nm to about 500 μm; from about 5 nm to about 100 µm.

In some embodiments, the width of the surface structures on a micrometer scale at the junction with the support substrate is from about 5 μm to about 500 μm. In some embodiments, the width of the surface structure on a micrometer scale is about 50 microns.

In some embodiments, the micrometer-scale length of the surface structures at the junction with the support substrate is from about 5 μm to about 500 μm. In some embodiments of the invention, the length of the surface structure on a micrometer scale is about 50 microns.

In some embodiments, the width of the nanometer-scale surface structures at the junction with the support substrate is from about 25 nm to about 5000 nm. In some embodiments, the width of the surface structure on a micrometer scale is about 250 nm.

In some embodiments, the length of the nanometer-scale surface structures at the junction with the support substrate is from about 25 nm to about 5000 nm. In some embodiments, the micrometer-scale length of the surface structure is about 250 nm.

In some embodiments, the height of the surface structure (ie, the height to which it protrudes from the support substrate) is from about 20 nm to about 5000 μm. In some embodiments, from about 40 nm to about 4000 microns; from about 55 nm to about 3000 μm; from about 75 nm to about 2500 μm; from about 100 nm to about 4000 μm; from about 250 nm to about 3500 μm, from about 20 nm to about 3500 μm; from about 2 nm to about 4000 μm; from about 20 nm to about 2500 μm; from about 20 nm to about 4000 μm; from about 20 nm to about 3000 μm; from about 20 nm to about 2000 µm. In some embodiments, from about 5 nm to about 750 microns; from about 5 nm to about 500 μm; from about 5 nm to about 100 µm.

In some embodiments, the height of the surface structure on a micrometer scale at the junction with the support substrate is from about 5 μm to about 500 μm. In some embodiments of the invention, the height of the surface structure on a micrometer scale is about 50 microns.

In some embodiments, the density of micrometer-scale surface structures provides from about 180,000 to about 1800 vertices or peaks per square centimeter to provide or form a functional surface thereon. In some embodiments, the density of micrometer-scale surface structures provides 18,000 vertices or peaks per square centimeter to provide or form a functional surface thereon.

In some embodiments of the invention, the height of the surface structure on a nanometer scale at the junction with the supporting substrate is from about 25 nm to about 5000 nm. In some embodiments of the invention, the height of the surface structure on a nanometer scale is about 250 nm.

In some embodiments, the density of nanometer-scale surface structures provides from about 160,000,000 to about 16,000,000,000 vertices or peaks per square centimeter to provide or form a functional surface thereon. In some embodiments, the density of nanometer-scale surface structures provides 1,600,000,000 vertices or peaks per square centimeter to provide or form a functional surface thereon.

In some embodiments of the invention, the functional surface is at or near the top of the surface structure.

In some embodiments, the functional surface is at or near the apex of the surface structure, and the surface structure tapers toward the apex and/or has a substantially triangular cross-section along a plane parallel to the top surface of the support substrate.

In some embodiments, the functional surface is at or near the top of the surface structure, and the width of the top of each surface structure is from about 1 nm to about 5000 μm. In some embodiments, from about 10 nm to about 10 μm, or from about 20 nm to about 2 μm, or from about 30 nm to about 1 μm. In some embodiments, from about 1 nm to about 1000 nm, or from about 1 nm to about 500 nm, or from about 1 nm to about 100 nm, or from about 1 nm to about 50 nm. The width of the top of each surface structure is less than at the junction with the supporting substrate.

In some embodiments, the functional surface is at or near the top of the surface structure, and the tops of the surface structures are separated from each other by a distance of from about 5 nm to about 1000 μm; from about 10 nm to about 1000 μm; from about 25 nm to about 1000 μm; from about 5 nm to about 750 μm; from about 5 nm to about 500 μm; from about 5 nm to about 100 μm (vertex to vertex). In some embodiments, from about 5 nm to about 2000 nm; from about 5 nm to about 1000 nm; from about 5 nm to about 500 nm (vertex to vertex).

In some embodiments, the support substrate comprises metal, composite material, polymer, silicon, or glass.

In some embodiments of the invention, the support substrate comprises one layer or more layers. In some embodiments, the support substrate is non-conductive, such as non-conductive polymer, glass and/or silica. In some embodiments of the invention, the support substrate is conductive. In some embodiments, the conductive material is doped silicon (Si), a semiconductor, a metal, a conductive polymer, a carbon-filled polymer, or a composite material. In some embodiments, the metal is a transition metal, including Ni, Cu, Al, Pt, Au, Ag, Mg and Mn.

In some embodiments of the invention, the surface structures are integral with the supporting substrate. In some embodiments of the invention, the surface structures are formed together with the supporting substrate. In some embodiments of the invention, the surface structures are made of the same material as the supporting substrate. In some embodiments of the invention, the surface structures and support substrate are composed of metal. In some embodiments, the support substrate and surface structures comprise a composite material, polymer, silica, or glass.

In some embodiments, the support substrate and surface structures comprise a first material, and the uniformly sized surface structures further comprise a layer covering them.

In some embodiments, the support substrate has a thickness of from about 50 μm to 5 mm. In some embodiments, the support substrate has a thickness of from about 1 mm to 2 mm; from about 85 μm to about 2 mm; from about 85 μm to about 1 mm; from about 1 mm to about 4 mm; from about 1 mm to about 3 mm; from about 85 µm to about 2 mm.

In some embodiments of the invention, the electrocatalyst is deposited on the top surface of the support substrate. In some embodiments of the invention, the electrocatalyst is applied to the top surface of the surface structures. In some embodiments of the invention, the electrocatalyst is deposited on the tops of the surface structure. In some embodiments of the invention, the electrocatalyst is a material other than the material of the surface structure and/or support substrate.

In some embodiments, the electrocatalyst is deposited on less than about 50% to about 0.000001% of the surface as viewed from above. In some embodiments, the electrocatalyst is applied to less than about 50% of the surface area, less than about 40%, less than about 30%, less than about 20%, less than about 10%, less than about 1%, less than about 0.01%, less less than about 0.001%, less than about 0.0001%, less than about 0.00001%, less than about 0.000001%. In some embodiments, the electrocatalyst is deposited on about 0.0000001%, or from about 0.000001% to about 50% of the surface area of the catalyst as viewed from above. Obviously, the smallest possible surface area is one atom on the supporting structure.

In some embodiments, the electrocatalyst is deposited on less than about 50% to about 0.0001% of the surface as viewed from above. In some embodiments, the electrocatalyst is applied to less than about 50% to about 0.1% of the surface as viewed from above. In some embodiments, the electrocatalyst is deposited on less than about 30% to about 0.0001% of the matrix surface as viewed from above.

In some embodiments of the invention, the electrocatalyst contains a layer of substantially constant thickness. In some embodiments, the thickness of the electrocatalyst is from about 1 nm to about 5 μm. In some embodiments, from about 20 nm to 500 nm, or from about 50 nm to 100 nm; from about 50 nm to 500 nm; from about 50 nm to 300 nm; from about 1 nm to about 3 μm; from about 3 nm to about 5 μm; from about 2 nm to about 4 µm. In some embodiments, the thickness of the electrocatalyst is greater than 0 nm but less than about 1 nm.

In some embodiments, electrocatalysts on the top surface of two or more surface structures are electrically coupled within the matrix.

Alternatively, the electrocatalyst is an integral part of the surface structure (or structures). In some embodiments of the invention, the electrocatalyst is integral with the supporting structure. In some embodiments of the invention, the electrocatalyst is made of the same material as the surface structure (or structures).

In some embodiments of the invention, the electrocatalyst contains a material that has a catalytic effect. In some embodiments of the invention, the electrocatalyst contains a conductive material. Conductive materials may include, but are not limited to, carbon (e.g., graphite, graphene, carbon fibers, carbon nanotubes, fullerenes), conductive polymers (e.g., polypyrrolidone (PPy), polyacetylene, metal, alloy, organometallic complex, or other similar conductive material. B In some embodiments, the electrocatalyst contains copper, a transition metal, an alloy, an organometallic complex, a transition metal-containing organometal complex, an organic material that can be oxidized or reduced.In some embodiments, the transition metal is selected from Ti, V, Cr, Fe, Co, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Ro, Pd, Ag, Cd, In, Sb, Sn, Cs, Ba, La, Ce, PR, Nd, W, Os, Ir, Au, Pb, Bi, Ra, U, Pt, Au and Ni. In some embodiments, the electrocatalyst contains nickel. In some embodiments, the organometallic complex and/or the transition metal-containing organometallic complex is selected from ferrocene, porphyrin, phenanthroline, porphyrin-imidazole, trispyridylamine and/or a transition metal triazole (ferrocene already contains a transition metal, and the porphyrin may further include a transition metal).

In some embodiments, the conductive solution contains water and/or an organic solvent. In some embodiments, the organic solvent is selected from alcohol (eg, ethanol), ether, acetonitrile, ethyl acetate, acetone, and/or DMSO.

In some embodiments of the invention, the conductive solution contains an electrolyte. In some embodiments, the electrolyte is selected from a buffer solution(s), a salt (eg, NaCl), or acid-base solutions (eg, _H2SO4 , _HNO3 , _NaOH )). In some embodiments, the solution contains a buffer solution with alkali metal chloride ions and copper 2+ ions.

In some embodiments of the invention, the active particles are in a gaseous or liquid state. In some embodiments, the active species is a gas that is passed through the conductive solution. In some embodiments, the gas is selected from hydrogen, oxygen, nitrogen, methane, carbon monoxide and/or carbon dioxide or air, or a mixture of any two or more of these. In some embodiments of the invention, the active particles are a liquid. In some embodiments, the liquid is water, methanol, ethanol, propanol, acetone, ammonia, short chain liquid hydrocarbons (eg, up to C21). When the active species is water, the conductive solution is preferably also water with an electrolyte or organic solvent. An organic solvent may be added to improve solubility or participate in oxidation or reduction processes.

The counter electrode performs redox charge balancing processes (oxidation or reduction, anode or cathode) and complements the redox processes (oxidation or reduction, anodic or cathode) occurring at the working electrode.

In some embodiments of the invention, preferably, the counter electrode, which performs the redox (oxidation or reduction) charge balancing processes and complements the redox (oxidation or reduction) processes occurring at the working electrode, is made of a material selected from the group consisting of inert conductive material, conductive material, metal, Pt, gold, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerene, conductive polymer PPy, PA, PA-acetylene or the same material as the working electrode. The counter electrode can be of various shapes and sizes, including fabric, flat, perforated sheet, fiber, mesh, or three-dimensional matrix, as defined herein. The 3D structures are expected to improve redox properties, including catalysis of the counter electrode, similar to what occurs at the working electrode as described in this paper.

In some embodiments of the invention, the counter electrode structure is planar or in the form of a matrix. For example, a matrix of pyramids, a matrix of cones, pyramidal, conical or ribbed. In some embodiments, the counter electrode comprises surface structures as described herein. In some embodiments, the shape of the counter electrode reflects the shape of the surface structures. In some embodiments, the counter electrode contains surface structures similar to the matrix of electrocatalysts. In some embodiments, the counter electrode includes surface structures that are not similar in size, geometry, or pattern to the electrocatalyst matrix.

In some embodiments, the counter electrode is (a) in a fixed orientation with respect to the surface structure, or (b) attached to the electrode array, or (c) held in an orientation necessary to minimize differences in distance between surface structures of the array, or (d) above the top surface of the array, or (e) includes three-dimensional surface features that are configured to promote the location of charge density (voltage or current) on the three-dimensional working electrode, for example, a series of peaks reflecting peaks of the working electrode.

In some embodiments, the counter electrode is positioned parallel to the surface structures.

The reaction at the counter electrode can be represented by any redox process. For example, this could be oxidation of alcohol, water or another component in addition to reduction on the surface structure, or vice versa.

In some embodiments, the counter electrode is made of a material selected from the group consisting of inert conductive material, conductive material, metal, Pt, Au, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerene, conductive polymer PPy, PA, PA -acetylene or the same material as the electrocatalyst matrix. In some embodiments, the counter electrode is a fabric, flat perforated sheet, fiber, mesh, or three-dimensional matrix, as defined herein. The 3D structures are expected to improve redox properties, including catalysis of the counter electrode, similar to what occurs at the working electrode as described in this paper.

In some embodiments, the potential difference between the counter electrode and the electrocatalyst is from about -2 V to +2 V. In some embodiments, from about -1 V to +1 V. In some embodiments, the potential difference is from about -200 mV to -1 V. Preferably, the potential difference is from about 0 mV to 1.8 V for oxidation.

In some embodiments, the current generated between the electrocatalyst and the counter electrode is substantially constant.

In some embodiments of the invention, the current generated between the electrocatalyst and the counter electrode pulsates between an activation potential and an inactivation potential. In some embodiments of the invention, the current generated between the electrocatalyst and the counter electrode pulsates between an activation potential and an inactivation potential within a range.

In one embodiment of the invention, the solution further comprises a reference electrode.

In some embodiments, the electrocatalyst matrix comprises a bonding layer, wherein the bonding layer is present either on a functional surface with a significantly higher density than a non-functional surface on the electrocatalyst matrix; or on a non-functional surface of the electrocatalyst matrix with a significantly higher density than at a point on the functional surface on the surface structure.

In some embodiments, the bonding layer comprises a self-assembled monolayer (SAM). In some embodiments, the SAM is present on the top surface of the electrocatalyst. In some embodiments of the invention, the SAM is present on the top surface of the support substrate. In some embodiments, the SAM is present near the surface structures such that the surface structure or portion thereof protrudes with an exposed functional surface thereon.

In some embodiments, SAM contains long chain molecules containing a carbon chain from C6 to C24, which may be an alkane, alkene, alkyne or aromatic substance. In some embodiments, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, or C24, or mixtures thereof.

In some embodiments, SAM comprises short-chain molecules containing a C10 carbon chain or less. In some embodiments, C1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, or mixtures thereof.

In some embodiments, the SAM is a mixed SAM containing long chain (C10 - C24, as above) and short chain (C1 - C10, as above) molecules, which may be alkanes, alkenes, alkynes, or aromatics. In some embodiments of the invention, the mixed SAM contains long chain molecules containing a carbon chain from C6 to C24 (as above) and short chain molecules from C1 to C5 (as above).

In some embodiments, the long chain SAM contains molecules selected from the group consisting of azides, amines, carboxylates, aldehydes, ketones, esters or carboxylic acids, or mixtures thereof. Such molecules are present at the core of SAM. In some embodiments, the short chain SAM contains molecules selected from the group consisting of alkanes, azides, amines, hydroxyls, carboxylates or carboxylic acids, or mixtures thereof. Such molecules are present at the core of SAM.

In one embodiment of the invention, the SAM contains a mixture of long chain molecules containing carboxylic acid molecules greater than C6 and short chain molecules containing hydroxyl molecules. In the above embodiments, the long chain SAM molecules are preferably selected from C6 to C24.

In some embodiments of the invention, SAM is present on the electrocatalyst matrix, but is absent from the top of the surface structure (including the functional surface) as defined above.

In some embodiments, the SAM contains short chain molecules containing a carbon chain of C5 or less, and wherein the upper portion of the surface structure (or structures) either (a) does not contain SAM, or (b) contains SAM intended to remove by creating a current between the electrocatalyst layer and the counter electrode.

In some embodiments, the SAM comprises a long chain SAM containing a carbon chain number of C6 to C24, and wherein the upper portion of the surface structure(s) either (a) does not contain a SAM, or (b) contains a SAM designed to removal by creating a current between the electrocatalyst layer and the counter electrode.

In one embodiment of the invention, the electrode matrix contains a SAM bonding layer on the top and bottom of the surface structure, and contact of the active particles with the functional surface results in selective removal of the SAM bonding layer from the top of the surface structure where the charge density (voltage or current) is focused. In this embodiment of the invention, the method further includes the step of selectively depositing an additional bonding layer on the exposed portion of the electrocatalyst layer on the functional surface.

In some embodiments, the SAM is selected from the group consisting of methyl-terminated alkanethiol, azide, thiol, aldehyde, cyanogen, diazonium, amines, alcohols, silanes, phosphonic acids, and carboxylic acids.

In specific embodiments of the invention, the SAM contains:

R-(aromatic) _n -SH, alkanes, alkenes, alkynes or aromatics, including both straight chains and chains consisting of amide and ester bonds

R-(CH ₂ ) _n -SH, R-(CH ₂ ) _n -NH ₂ , or

R-(CH ₂ ) _n -Si(OR') ₃

where R = alkyl, carboxylic acid, amine, aldehyde, alcohol, azide, quinone or tetrazine; And

R’ = Me, MeOH, Cl, (halide), Et, EtOH; And

where n=1 - 50.

In some embodiments of the invention, the conductive solution contains a dissolved reagent capable of attaching to the bonding layer. In some embodiments, the SAM contains a functional group that reacts with a dissolved reagent. In some embodiments, the functional group is a terminal functional group. In some embodiments, the SAM is functionalized with a functional group. In some embodiments, the functional group is selected from the group consisting of azide, carboxylic acid, amine, alcohol, ester, ketone, cyanogen, and aldehyde.

In some embodiments, the electrode array illustrated in step a) of the first aspects comprises a passivation layer disposed on a support substrate and covering a bottom portion of the surface structure and having an open top portion.

In some embodiments, the step of applying current or voltage to focus the charge density (voltage or current) results in the removal of the passivation layer from the functional surface at the top of the surface structures.

In some embodiments of the invention, the passivation layer is removed by applying a reduction or oxidation potential between the counter electrode and the electrode surface. In some embodiments, the potential is -2 V to +2 V, and in some embodiments, -200 mV to -1 V, and in some embodiments, -400 mV relative to the silver/silver chloride reference electrode .

In some embodiments of the invention, the passivation layer contains a functional group for attachment to the surface of the electrode. In one embodiment of the invention, the passivation layer comprises a tie layer as described and defined herein. In one embodiment of the invention, the passivation layer contains SAM. In some embodiments, the SAM is attached to the electrode surface by a sulfur atom. In some embodiments of the invention, the surface of the electrode is made of gold. In some embodiments, the SAM further contains a functional group, such as an alkyl chain, and in some embodiments, it further contains a carboxylic acid linked to an amine functional group.

The passivation layer between the vertices can be a photoresist, which is applied by spin coating, painting or sputtering. When this layer is dry or cross-linked, it becomes a passivation layer and helps focus the current. Ideally, this layer is a varnish or a UV cross-linked photoresist such as SU8. In some embodiments of the invention, the passivation layer or protective layer may include catalyst material that is located at an inactive location on the surface, for example, at locations other than or immediately adjacent to ridges, ridges and/or peaks.

In some embodiments, the adhesive layer is present on at least one of the following: a functional surface; surface structures; passivation layer; or carrier substrate.

In some embodiments of the invention, the method is applied to a fuel cell.

Those skilled in the art to which the invention relates will recognize many changes in design and widely varying embodiments and applications of the invention without departing from the scope of the invention as defined in the appended claims. The disclosures and descriptions herein are for illustrative purposes only and are not intended to be limiting in any way.

Additional aspects of the invention that should be considered in all its novel aspects will become apparent to those skilled in the art upon reading the following description, which provides at least one example of the practical application of the invention.

Brief description of drawings

Embodiments of the invention will be described below, given by way of example only, with reference to the accompanying drawings:

In fig. 1 shows a cross-section of an electrode array according to the invention with a triangular cross-section.

In fig. Figure 2a shows the rapid electrochemical desorption of a self-assembled monolayer (SAM) from a three-dimensional pyramidal electrode surface.

In fig. Figure 2b shows the slower electrochemical desorption of SAM from a flat electrode surface.

In fig. Figure 2c shows the kinetic curve of electrochemical desorption of SAM on three-dimensional and flat electrode surfaces.

In fig. 3, 4a and 4b show SAM images illustrating the deposition of Pt on top of a group of surface structures.

In fig. Figure 5a shows a systematic change in the mechanism of the O ₂ reduction reaction from a purely 2-electron process on a planar electrocatalyst to a partially 2-electron and partially 4-electron process on a micropyramidal electrocatalyst with and without an insulating layer, and to a pure 4-electron process on an electrocatalyst with a nanopyramidal structure. Various gold electrodes used in the example are shown in FIG. 5b. In fig. Figure 6 shows the absence of current in the background curve (upper line) and the increased catalytic current due to the introduction of CO ₂ (lower line).

In fig. Figure 7a shows curves for an organometallic catalyst (ferrocene) on flat and three-dimensional pyramidal electrode surfaces. In fig. 7b shows the corresponding Tafel plots for the curves in Fig. 7a.

In fig. Figure 8 shows the oxygen reduction curve of flat and three-dimensional pyramidal gold electrodes.

In fig. Figure 9 shows linear sweep voltammetry plots at 1600 rpm for various platinum (Pt) coated gold electrodes.

In fig. Figure 10 shows the oxygen reduction of 30% Pt/C deposited on planar and nanopyramidal structures.

In fig. Figure 11 shows the effect of three-dimensionality on the reduction of nitrate to nitrogen.

In fig. 12a (upper graph) and 12b (lower graph) show the dependence of the scanning speed of immobilized ferrocene on the pyramidal and flat electrode surface, respectively.

In fig. Figure 13 shows the peak potential as a function of scan rate for both ferrocene oxidation and reduction.

In fig. 14 shows the rotation speed curve for a pyramidal surface coated with platinum (Pt).

In fig. Figure 15 shows the Koutecki–Levich plot for both a pyramidal and a flat surface.

In fig. 16 shows the step-by-step manufacturing process of a three-dimensional electrode matrix.

In fig. 17 shows a) SEM images of a silicon master and b) SEM images of a nickel master created from a silicon master and c) SEM of an embossed gold plate.

In fig. 18 shows the production of hydrogen gas under identical conditions for A) flat surfaces compared to 50 µm pyramidal and B) flat surfaces compared to 250 nm pyramidal. SEM images for each of the pyramids are shown below in C (50 µm pyramid) and D (250 nm pyramid).

In fig. Figure 19 shows the curve of a phosphate-buffered saline solution bubbled with argon (top line) and argon + nitrogen (bottom line).

In fig. Figure 20 shows the reduction of CO ₂ . A) shows the curve for argon (top line) and argon + CO ₂ (bottom line), B) and C) show headspace analysis of the products and confirm the appearance of CO and formic acid.

In fig. Figure 21 shows oxygen reduction on a flat surface, a Pt-pyramidal (50 µm) and a Pt-nanopyramidal (250 nm) surface.

In fig. 22 shows the long-term reduction of O ₂ on a nanopyramidal Pt-coated surface using cyclic voltammetry.

In fig. 23 shows long-term _O2 reduction on a nanopyramidal Pt-coated surface using chronoamperometry.

In fig. 24 shows controlled deposition of Pt catalyst onto the top of the pyramids using A) 5 pulses and B) 10 pulses.

In fig. 25 and 26 show the structures mentioned in Table 2.

Detailed Description of Preferred Embodiments of the Invention

Definitions

“Attachment” or “binding” means covalent bonding, electrostatic bonding, or some other bonding method where the particles are bound in some way to a support. The binding can be done directly or through other particles.

"Conical" refers to the transition from a wider surface structure to a narrower surface structure.

"Deposited" means formed on a surface and can refer to any form of formation, layering or production. In one embodiment of the invention, deposition is achieved by sputtering, electron beam or thermal evaporation. Preferably, the deposited layer has some degree of adhesion to the layer on which it is located. This coupling may be covalent, electrostatic, or may involve van der Waals forces.

"Substantially constant thickness" with respect to the electrocatalyst means that the electrocatalyst does not change significantly depending on the degree of coverage of the support substrate or tie layer. It is intended that unintentional changes in layer thickness that do not substantially affect sensor performance are included in the term “substantially constant thickness.”

“Include/contain,” “containing,” etc., unless the context clearly requires otherwise, should be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense, that is, in the sense of “including, but not limited to.”

The terms "surface structure" and "functional surface" as used herein are intended to refer to single or multiple structure/surfaces.

The "width" of the surface structure is measured by the largest distance across the cross-sectional area of the surface structure, where the cross-sectional plane is substantially parallel to the top surface of the support substrate. Where width is mentioned, it also describes the point on the surface structure at which the parallel plane is located (for example, at the junction between the support substrate and the surface structure).

"Catalyst" refers to substances that increase the rate of a chemical reaction.

“Electrochemically modified” in relation to active species means that the active component is subject to reduction or oxidation, i.e. gain or loss of electrons.

"Dissolved reactant" means a reactant in solution that takes part in a reaction catalyzed by the active catalyst species. The dissolved reagent is preferably in another conductive solution (i.e., different from the conductive solution containing the active species) or may be in the same solution and, upon interaction with the active species, serve to bind/react with the target molecule to be detected by the sensor .

The "bonding layer" includes a layer of molecules attached to the surface of the electrode matrix. The bonding layer can be formed from a cross-linked polymer, a photoresist, or a self-assembled monolayer (SAM). Preferably, the cross-linked polymer is a negative epoxy photoresist such as SU-8. The bonding layer can be applied to the surface of the electrode matrix by methods known to those skilled in the art, for example by spinning, spraying, dipping, rubbing or painting. In alternative embodiments of the invention, the tie layer is attached to the surface of the electrode matrix by electrochemical modification of the tie layer precursor (ie, active species), preferably in accordance with the methods described herein.

"Focused" in relation to electric current or voltage means that the charge density (voltage or current) is higher at a focused position on a surface compared to another position on the surface. The charge density (voltage or current) at a surface can be measured by methods known to those skilled in the art. However, in one embodiment of the invention, the charge density (voltage or current) is measured by modeling and then targeting a fluorophore or depositing platinum on a surface.

A "counter electrode" can be any conductive element that facilitates the flow of current from the electrode layer through the solution. In one embodiment of the invention, the counter electrode comprises a wire or other form of electrode structure held in solution. Preferably, the counter electrode is made of a material selected from the group consisting of metal, platinum, gold, nickel, copper, iron, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerene, conductive polymer PPy, PA, polyacetylene, stainless steel. The counter electrode can be made of a solid layer or a conductive layer deposited on a suitable substrate, for example, polymer glass, metal. The counter electrode may also be pure metal (Au, Pt, stainless steel, copper) or an Au or Pt coated substrate (metal, polymer or glass) and may have three-dimensional surface features designed to promote charge density (voltage or current) on the working three-dimensional electrode. For example, this could be a series of peaks reflecting the peaks of the working electrode.

"Activating" or "activating" means converting active species from an inactive form to a reactive form. Thus, "electrochemical activation" means the conversion of active species into a reactive form by oxidation or reduction by applying a current to the electrode.

"Activation potential" means the voltage (oxidative or reduction in the typical range of +2 V to -2 V) required to initiate a binding/addition/modification reaction. Typically, the restoring activating potential for a short pulse is between -500 mV and -100 mV.

“Inactivating potential” means the voltage required to stop a binding/addition/modification reaction.

"Active species" means a substance present in a solution that can undergo electrochemical modification. In one embodiment of the invention, the active species is a catalyst or a catalyst precursor. In another embodiment of the invention, the active particles are a component of the binder layer. In another embodiment of the invention, the active particles are a charged particle capable of attaching to a functional surface. In another embodiment of the invention, the active particles are a coupling agent capable of detecting a target analyte in solution.

"Oxidation" means a chemical reaction that loses electrons. Therefore, "oxidizing" means promoting the loss of electrons in a chemical reaction.

"Reduction" means a chemical reaction that gains electrons. Therefore, "reductive" means facilitating the acquisition of electrons in a chemical reaction.

"Pulsing" or "pulsating" means modulation of voltage or current from an activating potential to an inactivating potential. The pulsation may be regular or intermittent.

"Self-assembled monolayer (SAM)" refers to molecular aggregates containing head groups associated with a tail group that ends with a functional group.

“Selective removal,” when referring to the removal of a substance from a functional surface, means that removal is enhanced relative to another surface on the matrix that is not receiving current focus. For example, SAM removal will occur at a faster rate, or a greater concentration of the substance will be removed compared to other surfaces. This wording does not mean that removal will be complete or that removal will not occur to a lesser extent on other surfaces.

"Selective deposition" when applied to the deposition of a substance onto a functional surface means that the deposition is enhanced relative to another surface on the matrix on which the current is not focused. For example, deposition of SAM will occur at a faster rate, or a greater concentration or density of material will be deposited compared to other surfaces. This formulation does not exclude the possibility that deposition occurs to a lesser extent on other surfaces.

“And/or” means “and” or “or” or both.

"(s)" after a noun refers to the plural and/or singular forms of the noun.

Reference to a range of numbers specified herein (e.g., 1 to 10) is intended to also include reference to all rational numbers within that range (e.g., 1; 1.1; 2; 3; 3.9; 4; 5; 6; 6.5; 7; 8; 9 and 10), as well as any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5, and 3.1 to 4, 7).

Description

The inventors have found that the process according to the invention reduces the costs associated with typically expensive catalytic materials. Cost reduction is achieved in one or more of the following ways:

1. Increasing the activity of the catalytic material

2. Reducing the amount of catalytic material required

3. Possibility of replacing with a cheaper catalyst with lower activity without loss of efficiency

4. Reducing the amount of energy required for a reaction to occur

5. Increase in current exchange density

6. Increasing the rate of mass transfer between the reagent and catalyst

7. Increasing the rate of mass transfer of the product/products from the catalyst

The inventors have discovered that by modifying the surface of an electrode to form an electrocatalyst with an array of surface structures, when current or voltage is passed through the electrocatalyst exposed to a conductive solution, the charge density (voltage or current) can be focused towards the apex (or peak) of the surface structures. This can lead to dramatic improvements in electrocatalytic reactions. The inventors observed not only a kinetic enhancement, that is, a sharp increase in the rate of catalysis, and a thermodynamic improvement (for example, hydrogen production from water increased by more than 100 times), that is, a sharp reduction in the energy required to carry out a catalytic redox reaction on a similar flat surface. electrocatalyst, but also unexpectedly revealed a change in the reaction mechanism. For example, during the electrochemical reduction of oxygen in an aqueous alkaline medium, pure peroxide (H ₂ O ₂ ) is usually formed. However, unexpectedly, when using the method according to the invention, water was obtained. Possible recovery paths:

The method according to the invention unexpectedly promotes a more efficient 4-electron process (see example 3). This may result in reduced energy losses and/or overcome problems associated with O ₂ reduction as a rate determining step. This may be particularly advantageous when used in, for example, a fuel cell, as it may provide improved cell performance.

This 4-electron process could be observed almost exclusively when using nanosurface structures, but it was also observed in particular when using microsurface structures.

Further redox reactions in which the method may be applied include, but are not limited to:

release of hydrogen from water;

release of oxygen from water;

hydrogen oxidation;

carbon dioxide to carbon monoxide;

carbon dioxide to methanol;

carbon dioxide to carboxylic acid (eg formic acid);

carbon dioxide to aldehyde and/or ketone;

carbon dioxide to methane, ethane, propane and/or higher order carbon chains up to _C21 ;

oxidation of methane to methanol;

nitrogen to ammonia;

splitting ammonia into hydrogen and nitrogen.

Applications of the method according to the invention include (but are not limited to) electrodes, batteries, fuel cells and/or hydrogen production.

Standard electrodes include a conductive solid substrate with a catalyst fixed to the surface. Examples of a conductive solid substrate include, but are not limited to:

• polymer, glass or silicon coated with metal

• carbon mesh

• carbon material (fibers, vulcan, powder, glassy material, cutting plane, basal plane, fullerenes, nanotubes, graphene)

• metal sheet, perforated and non-perforated

• ITO (Indium Tin Oxide) or FTO (Fluorine Tin Oxide) coated sheet (polymer, glass, silicone)

• conductive polymer

The inventors believe that catalysis depends on a combination of factors:

1. Diffusion of reactants and product both to and from the site of catalysis

2. Electron supply:

a. An oxidative process that requires the supply of electrons to the site of catalysis.

b. A reduction process that requires the removal of electrons from the site of catalysis.

3. The voltage at the site of catalysis is sufficient to carry out the catalytic process.

4. Easy electron transfer between reactant and catalyst

5. Reducing activation energy for conversion

6. Catalyst material used.

3D provides a platform to achieve the above factors in a controlled manner and improves the performance of existing catalysts that are either deposited directly on top of 3D structures or suspended in a matrix surrounding the peaks. This allows access to multi-electron transfer transformations (oxidative or reductive) that were previously unavailable and the controlled production of more products from the same starting material using the same catalyst.

As will be apparent to the skilled reader, if the description of the invention refers to a solution containing both the active species and a counter electrode, this refers to the solution containing the position of the counter electrode.

Without wishing to be bound by theory, the inventors believe that the observed increase in kinetic and thermodynamic rates, the sharp increase in reactivity of the electrocatalyst at the peaks, and/or an alternative reaction path may be caused by one or more of the following mechanisms:

The combination of high-density voltage and current distribution results in less voltage loss (that is, the voltage at the peak is significantly higher, therefore lower resistance) and the production of more reactive electrons.

Hot electrons are generated due to the plasmonic effect, resulting in easier electron injection.

The combined effect of higher voltage, higher current density, lower resistance, and faster diffusion of the catalyst particles results in a supercharged state of the catalyst particles.

The above, in combination with the electromagnetic effect, influences constants such as potential field, concentration gradients, temperature and pH.

The quantum effect, which increases as a smaller effective peak size or particle size is obtained in the hot electron environment, is caused by the environment near the peaks. The result is an increased current density of hot electrons to drive the reaction. This quantum effect increases as the peak sizes decrease.

Fast diffusion, combined with the above environment and small effective surface area, changes the substrate binding modes and results in increased reactivity.

Reducing the IR radiation drop due to a combination of the above-mentioned reduction in “energy loss” and therefore the energy required for the reaction.

Reduced solution resistance due to environmental influences, caused by a combination of effects as described above.

Quantum effect that results in improved substrate bonding orientation.

Quantum effect due to a change in substrate binding modes to a higher substrate concentration (e.g. H ⁺ ) over a smaller surface area due to differential current and potential density.

Reducing the activation energy of the catalytic process.

Change in the density of the catalyst state.

Change in the Gibbs free energy of an equilibrium process.

Increasing the enthalpy of the reaction and, therefore, facilitating the reaction.

Entropy effect

Higher order

High current density and/or higher peak temperature.

As will be apparent, the surface structures protruding from the support substrate create a three-dimensional (3D) structure on the matrix.

In one embodiment of the invention, the surface structures are integral with the supporting substrate. This means that the surface structures are made of the same material as the supporting substrate and protrude from it. In this embodiment of the invention, the top surface of the support substrate may comprise an array of surface structures arranged in an ordered or random configuration. In this embodiment of the invention, the electrocatalyst may be formed/applied to the top surface of the surface structures (and the support substrate where exposed), or the electrocatalyst may also be made of the same material as the surface structures and/or the support substrate. The support substrate with integrated surface structures can be formed by known methods, such as hot stamping, CFT processing, injection molding, stamping, electroforming, lithography and the like.

In an alternative embodiment of the invention, the surface structures are formed from a material different from the material of the support substrate and are applied or attached to the support substrate. In this embodiment of the invention, the surface structures may be an integral part of the electrocatalyst. This means that the surface structures are part of the electrocatalyst and are formed from the same material as the electrocatalyst.

Alternatively, the electrocatalyst may be deposited on or otherwise formed on surface structures, and said surface structures are deposited on, integral with, or otherwise formed on a support substrate. The carrier substrate with surface structures formed from other materials can be produced by known methods, such as hot stamping, CFT processing, laser processing with photoresist, stamping or lithography methods, and deposition methods such as carbon material growth or vapor deposition .

It is particularly preferred that the electrocatalyst can be deposited or otherwise formed on surface structures. The inventors have found that this is cost effective because it requires less catalyst. Catalysts are often expensive materials such as platinum and/or gold. The ability to use small amounts of catalyst is very advantageous. The inventors have discovered that using small amounts of catalyst results in the same or even better performance than a planar electrode where much more catalyst is used.

The invention also (or alternatively) allows the replacement of an active, but usually more expensive catalyst, with a less expensive catalyst that is less active under standard conditions. For example, if cost is an important factor, the catalyst may be copper, titanium, or nickel instead of platinum, palladium, rhodium, iridium, or gold. It is believed that with the increased efficiency of electron transfer from surface structures to active agents, a cheaper catalyst such as nickel can be used to replace a more expensive catalyst such as platinum. Additionally, the amount of catalyst focused on the peaks, tops, ridges and/or edges of surface structures minimizes the amount of extraneous catalyst that might otherwise be located above other structures or in the valleys between structures, again resulting in cost savings. even when using more expensive catalytic materials. The cost and activity of a number of catalysts are shown in Table 1.

Table 1. Exchange current density of the hydrogen evolution/anodic oxidation reaction of various catalytic materials in 1 mol/kg H ₂ SO ₄

Catalytic material Exchange current density Current price in US dollars ( 02/28/2019 ) Palladium 1.0 x 10 ^-3 $1533/oz Platinum 8.0 x 10 ^-4 $870/oz Rhodium 2.5 x 10 ^-4 $2705/oz Iridium 2.0 x 10 ^-4 $1485/oz Nickel 7.0 x 10 ^-6 $0.36/oz Gold 4.0 x 10 ^-6 $1320/oz Titanium 7.0 x 10 ^-8 $1.61/lb

In some embodiments of the invention, the cross-sectional area of the surface structure is reduced along an axis orthogonal to the top surface of the support substrate. In some embodiments, the top portion of the at least one surface structure has a convex top surface. More preferably, the surface structure has a triangular, convex, semicircular or papillary cross-section along a plane orthogonal to the top surface of the support substrate.

The top of the surface structure preferably has an angle of about 90° or less at the apex, for example, the surface structure extends into a tip. It is believed that the sharper the angle, that is, the sharper the tip, the stronger the effect on the electrocatalyst. In some embodiments, the surface structures are pyramidal, conical, ridge structures, or combinations thereof. In some embodiments, the surface structure has a substantially triangular, substantially circular, or substantially square cross-section along a plane parallel to the top surface of the support substrate.

In a preferred embodiment of the invention, the surface structures are uniformly distributed on the support substrate, although this can be changed if necessary. Uniformity is preferable because it leads to more predictable behavior and results. Also, the amount of catalyst is limited to a narrow region at the tops of the peaks. This results in the catalyst activity remaining constant and the product becoming purer.

In some embodiments of the invention, the catalyst may be applied in a controlled manner to a functional surface (e.g., ridges, vertices, peaks, and/or other surfaces of surface structures) by exposing the functional surface to one or more of the following methods: but not limited to, electroplating, electroplating, electroplating , sputtering, electron beam deposition, vapor deposition, thermal evaporation, plasma deposition.

In some embodiments, controlled deposition may be accomplished by varying one or more of the following deposition parameters, among others: voltage, current, time (time the functional surface is exposed to the deposition method, such as immersion time in an plating solution), pulse frequency ( e.g., electrodeposition pulse frequency) and a passivation layer (e.g., using a passivation layer to expose a partial surface of the surface structure, which may, for example, change the electrodeposition current density). It should be understood that any fabrication methods described herein can be used to control catalyst deposition, such as lithographic masking, SAM.

The surface structures preferably have substantially uniform dimensions. As the inventors have shown, the size of surface structures affects the activity of the catalyst and the product of the redox reaction. Uniformity in the size of surface structures is preferred as it results in a more predictable and repeatable product. The size of the surface structures can be selected depending on the required product or product ratio. The resulting product can also be practically homogeneous.

In an exemplary embodiment of the invention, the surface structures and catalyst may be configured to produce primarily a predetermined primary or preferred product. Alternatively, the surface structures and catalyst may be configured to produce one or more predetermined products, for example, a preferred or primary product, and a secondary product (which may also be preferred). Likewise, the surface structures and catalyst can be configured to minimize the production of undesired product.

The surface structures preferably have at least one line of symmetry and, more preferably, the surface structures have at least two lines of symmetry. This is preferred so that the conductive solution surrounds the top of the surface structure.

The width of the surface structure at the junction with the supporting substrate, in some embodiments, is from about 20 nm to about 5000 μm, in some embodiments, from about 40 nm to about 4000 μm; from about 55 nm to about 3000 μm; from about 75 nm to about 2500 μm; from about 100 nm to about 4000 μm; from about 250 nm to about 3500 μm, from about 20 nm to about 3500 μm; from about 2 nm to about 4000 μm; from about 20 nm to about 2500 μm; from about 20 nm to about 4000 μm; from about 20 nm to about 3000 μm; from about 20 nm to about 2000 µm. In some embodiments, from about 5 nm to about 750 microns; from about 5 nm to about 500 μm; from about 5 nm to about 100 µm. Particularly preferred surface structures are nanostructures, although microstructures are also advantageous, depending on the desired product.

The functional surface is preferably at or near the top of the surface structure. Although the entire surface structure may be made of electrocatalyst material, it is the apex or apex that is considered to be the functional surface that provides most of the catalytic effect of the redox reaction. Preferably, electrochemical activation of the catalyst occurs at a substantially higher rate on the functional surface than elsewhere on the surface on the electrocatalyst layer.

In some embodiments, the functional surface is at or near the apex of the surface structure, and the surface structure tapers toward the apex and/or has a substantially triangular cross-section along a plane parallel to the top surface of the support substrate. The functional surface is, in some embodiments, at or near the top of the surface structure, and the width of the top of each surface structure is from about 1 nm to about 5000 μm, in some embodiments from about 10 nm to about 10 μm, or from about 20 nm to about 2 μm, or from about 30 nm to about 1 μm. In some embodiments, from about 1 nm to about 1000 nm, or from about 1 nm to about 500 nm, or from about 1 nm to about 100 nm, or from about 1 nm to about 50 nm. The width of the top of each surface structure is less than at the junction with the supporting substrate.

In some embodiments, the vertices of the surface structures are separated from each other by a distance of from about 5 nm to about 1000 μm; from about 10 nm to about 1000 μm; from about 25 nm to about 1000 μm; from about 5 nm to about 750 μm; from about 5 nm to about 500 μm; from about 5 nm to about 100 μm (vertex to vertex). In some embodiments, from about 5 nm to about 2000 nm; from about 5 nm to about 1000 nm; from about 5 nm to about 500 nm (vertex to vertex).

It should be understood that the surface structures of any of the embodiments herein include any suitable surface features that effectively increase the relative surface area and/or provide multiple vertices or peaks compared to a flat, smooth area of equivalent size. The size, shape, density, uniformity, arrangement and proportions of the elementary parts of the matrix of surface structures may differ from the described embodiments of the invention.

In one embodiment of the invention, the surface structures may have a uniform shape and/or geometry, density and/or size. The surface structures may have a shape, size and/or density in accordance with a predetermined characteristic, for example, the presence of a number or size of vertices or peaks for a particular solution to be catalyzed, or a desired shape, size, density or uniformity of vertices or peaks, according to as necessary.

In alternative embodiments of the invention, the surface structures may have a non-uniform size, shape and/or density. For example, surface structures may have uniform protrusion heights and shapes, but varying protrusion spacing or densities. Alternatively, the surface structures may have different heights but uniform shape, spacing, or density. It should be understood that any change in the shape, size and/or density of the surface structure can be made to facilitate a particular reaction or catalysis due to the presence of a vertex or peak, or a plurality of vertices or peaks, that act as a functional surface, or allow the formation of a functional surface thereon.

Examples of the shapes of the surface structures may be substantially conical, cylindrical or pyramidal, pointed, jagged, square, pentagonal, pentagonal or hexagonal. In a preferred embodiment of the invention, any apex or peak forming shape suitable for use as a functional surface or for forming a functional surface for catalysis can be used.

In a preferred embodiment of the invention, a homogeneous matrix of surface structures can advantageously provide a substantially homogeneous product or result of catalysis from solution. This may be due to the uniform ridges, vertices, and/or peak sizes and shapes of each surface structure, which may provide uniform current density through each vertex or peak of the surface structure.

In alternative embodiments of the invention, a heterogeneous matrix of surface structures may advantageously enable the production of multiple products or catalytic outputs from solution. This may be due to the different sizes of vertices or peaks with different geometries of surface structures in such a heterogeneous matrix, resulting in varying current density at the vertex or peak. For example, a first group of surface structures may be uniform in size, and a second group, different in size from the first, is also uniform in size within the second group.

In fig. 1 shows an embodiment of the invention in which an electrocatalyst matrix 400 includes a support substrate 410, surface structures 415, and a functional surface 420. The functional surface is formed from an electrocatalyst (eg, Pt, Au, Ni) that is activated by electrochemical modification via current or voltage between the electrocatalyst and a counter electrode.

The matrix optionally includes a catalyst at the top of the surface structure and a cocatalyst in the valleys between the surface structures.

The active particles in some embodiments of the invention undergo electrochemical modification upon contact with the functional surface, and the thermodynamic efficiency and kinetic efficiency of the electrochemical modification are improved compared to a corresponding planar electrode.

In some embodiments, the electrocatalyst matrix includes part of the system. The system contains suitable wiring, seals, electrodes and solutions to allow the sample to contact the functional surface and enable electrochemical modification of the active species. The system preferably includes a container, channel (eg, within or for an electrode package), or other vessel for holding the conductive solution on the functional surface. The matrix system also preferably further comprises a reference electrode and a counter electrode configured to contact the conductive solution during the redox reaction. Preferably, the reference electrode and/or counter electrode are stationary and at a fixed distance from the functional surface. Suitable systems and configurations should be known to those skilled in the art.

It will be apparent to one skilled in the art that the electrocatalyst matrix (the "working electrode") can act as an anode when an oxidation reaction occurs or as a cathode when a reduction reaction occurs. The term "working electrode" is often used in the art to describe the electrode at which a reaction of interest occurs. However, a counter electrode is required to balance the redox charge. For example, if oxidation occurs at the working electrode, reduction will occur at the counter electrode.

In some embodiments, the counter electrode can also be used to conduct useful redox reactions. In this case, the counter electrode can be flat or have a matrix structure. In some embodiments, the counter electrode includes a support substrate and surface structures similar to those described for the electrocatalyst matrix. All features of the surface structures described herein with respect to the electrocatalyst may apply to the counter electrode. The surface structures of the counter electrode may have the same size and/or geometry as the electrocatalyst, or may have a different size and/or geometry than the electrocatalyst.

Alternatively, the counter electrode of any embodiment of the invention comprises a substantially inert conductive material. In this case, the term "inert" means that the counter electrode is substantially unchanged in mass and condition after current is applied and passed from the electrocatalyst to the counter electrode. Consequently, the “inert” counter electrode practically does not react with the components of the solution. Preferably, the counter electrode is made of a material selected from the group consisting of metal, platinum, gold, nickel, copper, iron, carbon, graphite, graphene, carbon fiber, carbon nanotubes, fullerene, conductive polymer PPy, PA, polyacetylene, stainless steel. The counter electrode can be made of a solid layer or a conductive layer deposited on a suitable substrate, for example, polymer glass, metal. The counter electrode can be made of a solid layer or a conductive layer deposited on a suitable substrate, for example, polymer glass, metal. Preferably, the counter electrode is a bare metal (such as Au, Pt, stainless steel and/or copper) or an Au or Pt coated substrate (such as metal, polymer and/or glass). Preferably, the counter electrode of any embodiment of the invention is in a fixed orientation with respect to the surface structure.

Preferably, the counter electrode according to any embodiment of the invention is attached to the electrode matrix.

Preferably, the counter electrode is held in a specific orientation to minimize the difference in distance between each of the surface structures of the array. Preferably, the counter electrode is located above the top surface of the matrix. In these embodiments, the distance from the counter electrode to the top of each surface structure is substantially the same (equidistant). This minimizes detection interference caused by counter electrode placement.

Therefore, it is preferable that the counter electrode (a) be in a fixed orientation with respect to the surface structure, (b) attached to the electrode array, (c) held in the desired orientation to minimize the difference in distance between each of the surface structures of the array, or (d ) was located above the upper surface of the matrix.

In one embodiment of the invention, the solution further comprises a reference electrode. The reference electrode helps measure and monitor voltage while current is flowing, such as during the deposition process. The properties and location of the reference electrode should be known to those skilled in the art.

Preferably, the electrode matrix further comprises a reference electrode in contact with the solution. Preferably, the reference electrode includes an electrode made of Ag/AgCl. Other options include the following: standard hydrogen electrode (SHE); normal hydrogen electrode (NHE); reversible hydrogen electrode (RHE); dynamic hydrogen electrode (DHE); standard calomel electrode (SCE); copper(II) sulfate electrode (CSE); mercury sulfate electrode; Pt, stainless steel, Au.

Preferably, the current supplied between the electrocatalyst and the counter electrode, measured at the electrocatalyst, is an oxidation or reduction current. This facilitates the electrochemical modification of the active species after contact with the functional surface of each surface structure.

Preferably, the current contains a reduction or oxidation potential between the counter electrode and the electrode surface. Preferably, the potential is from about -2 V to + 2 V, from about -200 mV to -1 V, or about -400 mV relative to the silver/silver chloride reference electrode.

Preferably, the current according to any embodiment of the invention pulsates between an activating potential and an inactivating potential. This pulsation allows the reaction occurring on the functional surface to be localized. Pulsation also maximizes the number of active species attaching to the top of each surface structure and minimizes the diffusion of active particles from the top of each surface structure into solution. The pulsation frequency and its duty cycle determine the degree of localization on the functional surface. A regular on/off cycle deactivates the active particles so that the spread of activated active particles from the functional surface to other locations on the matrix is minimized.

Before current is applied, the sensing agents remain inactive and the active species present in the solution cannot bind to the sensing agents. When an activating potential is applied, the charge density (voltage or current) at the functional surface increases, thereby activating any active species that diffuses to the functional surface.

Accordingly, the current in any embodiment of the invention pulsates between an activating potential and an inactivating potential.

The entire disclosure of all applications, patents and publications cited above and below, if any, is incorporated herein by reference.

Reference to any prior art in this description is not and should not be taken as an endorsement or any form of suggestion that such prior art is part of the generally known knowledge in the field of interest anywhere in the world.

In a broad sense, the invention can be said to consist of the parts, elements and features mentioned or specified in the specification of the application, individually or together, in any or all combinations of two or more of the mentioned parts, elements or features.

If reference was made in the above description to integers or components having known equivalents, those integers are included in this description as if they were given separately.

It should be noted that various changes and modifications to the presently preferred embodiments of the invention described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing the advantages associated therewith. It is therefore intended that such changes and modifications be included within the scope of the invention.

Examples

Materials

Containers containing phosphate buffered saline (PBS), K ₃ FeCN ₆ , K ₄ FeCN ₆ , K ₂ PtCl ₄ and thiols were purchased from Sigma Aldrich and used unchanged.

The electrodes used in these experiments were made of gold-coated polycarbonate. The electrode matrix was made of polycarbonate, on which a number of pyramids were extruded.

The micropyramidal structures had a peak-to-peak distance of 70 μm and a base of 50 μm x 50 μm. The peak size ranges from 1 to 5 microns. The height of micropyramids is about 35 microns.

The nanopyramids were purchased as a stamped nickel matrix and consisted of a series of peaks measuring 250 nm at the base and 3 to 10 nm at the peak. The peak-to-peak distance (from the top of a surface structure to the top of the next surface structure) was about 250 nm, and the peak size ranged from 3 to 10 nm. The height of the nanopyramids is about 250 nm.

Electrochemical research

Electrochemical studies were carried out using a Pine E-chem bipotentiostatic setup in a three-electrode arrangement with platinum as the counter electrode.

All electrochemical potentials presented in this work are measured and evaluated using a sealed miniature Ag/AgCl reference electrode (eDAQ). The electrochemical cell was enclosed in a Teflon cone with a cylindrical hole (inner diameter 4 mm) pressed against the sample. All measurements were carried out at room temperature without excluding air.

Formation of a self-assembled monolayer (SAM)

Precipitation solutions were prepared by dissolving the required amount of alkanethiol in ethanol. The total thiol concentration was maintained between 0.1 and 1 mM. Freshly prepared gold substrates were immersed in the deposition solution for 24 hours. Deposition occurred in the absence of light to prevent any photonic oxidation on the thiol monolayers. The substrates were then washed with ethanol and deionized water to remove excess adsorbate and then dried with N2 to remove residual solvent.

Example 1: Removing SAM from a Peak

Objective: To demonstrate that the distribution of charge density (voltage or current) in an electrode matrix with surface structures can be used to selectively remove a self-assembled monolayer from the tops of surface structures.

Method: SAM coated electrodes were immersed in phosphate buffered saline (PBS). Desorption was carried out by chronoamperometry using a reduction potential (-1.1 V for a cumulative duration of 0 s, 2.5 s, 5 s, 10 s, 20 s, 40 s, 80 s, 160 s, 320 s, 640 s and 900 s ), and the desorption rate was monitored using cyclic voltammetry in K ₃ FeCN ₆ at 20 mV/s.

Results: Gold-coated surface structures on the electrode matrix exhibited a faster desorption profile with a maximum oxidation peak occurring at approximately 10 seconds (Figure 2a) compared to the planar electrode (Figure 2b), with a maximum oxidation peak occurring at approximately 20 seconds. -30 minutes.

Conclusion: The distribution of differential charge density (voltage or current) on the 3D surface resulted in significantly faster desorption of SAM from the peaks of surface structures compared to the flat surface (Figure 2c). This was due to the concentration of charge density (voltage or current) at or near the top of the surface structures. This makes it possible to change the functional surface of the electrocatalyst or to expose only the peak, that is, the functional surface of the electrocatalyst.

Example 1b. Passivation layer SU8

Purpose: To demonstrate that the distribution of charge density (voltage or current) in the electrode matrix can be increased by applying a photoresist coating in the recesses between the peaks.

Method: Gold-coated electrodes had a layer of SU8, spin-coated on the surface at 2000-5000 rpm, and cross-linked under the influence of UV radiation. This should provide a passivation layer thickness in the range of 10 µm to 30 µm.

Results: Platinum was electrochemically reduced at the open peaks, forming as a series of nanoparticles as a result of current focusing (see Figure 3).

Conclusion: The differential charge density (voltage or current) is enhanced by the passivation layer and causes the formation of nanoparticles instead of a film, which can lead to enhanced catalytic activity.

Example 2: Pt Functionalization at its Peak

Objective: To demonstrate that the differential charge density (voltage or current) distribution of an electrode array with surface structures can be used to selectively deposit metals on top of the structures.

Method: Surface structures with a gold electrocatalyst layer were cleaned by reactive ion etching (RIE) with O ₂ plasma (2 min) and immersed in a solution of platinum (IV) chloride (1 mM) in PBS. The growth of Pt meso particles was carried out using a square wave potential as follows: a reduction potential (−500 mV) was used to reduce Pt(II) to Pt(0) at the surface within 15 s, and then an oxidation potential (300 mV) was used to stopping the process. This cycle continued until the desired amount of sedimentary Pt was obtained.

Results: Pt deposition occurred predominantly at or near the top of surface structures, as shown in FIG. 4a and 4b (without passivation) and FIG. 3 (with SU8 passivation layer).

Conclusion: Due to the higher charge density (voltage or current) distribution at or near the top of the surface structure, Pt is deposited at a higher density than on other surfaces. This makes it possible to modify the functional surface of the electrocatalyst.

Example 3: Nanoscale Transition Metal Catalysis and Mechanism Change

Objective: To demonstrate that the three-dimensionality of an electrocatalyst changes the reaction mechanism and its efficiency in converting to a product, minimizing the "leakage" of electrons through the formation of a by-product. This reduces catalytic efficiency and can lead to the formation of byproducts that damage the reaction.

Method: A 4-electrode system (Pt, 2 _H2O2 working collector electrodes and 1 Au electrode as the O2 reduction catalyst working electrode ₎ was used with Pt as the counter electrode and Ag/ _AgCl as the reference electrode to measure the hydrogen peroxide level , formed during the oxygen reduction reaction through planar, micropyramidal and nanopyramidal surface structures. The collector height (Pt) was calibrated by lowering the Pt working electrode to the surface of the Au electrode. From this baseline it rose up to 200 µm. Cyclic voltammogram was performed on gold electrodes while the Pt electrode was kept at an oxidation potential sufficient to oxidize H ₂ O ₂ . The _O2 reduction efficiency was then assessed as the ratio of Pt to Au current.

Results: the results are shown in Fig. 5a for various gold electrodes (as shown in Fig. 5b): flat, micropyramidal, micropyramidal, insulated with an inert layer between the tops of the pyramids (called pyramidal varnish in the figure) and nanopyramidal at pH 13. Under these conditions, gold is known to produce pure H₂O₂ (hydrogen peroxide) during electrochemical reduction of O₂ in an alkaline environment. Therefore, hydrogen peroxide would be the expected product for this type of reaction. The introduction of three-dimensionality, in particular nanostructures, but to a lesser extent microstructures, unexpectedly changes the mechanistic behavior, moving from 2-electron reduction (100% H₂O₂) to 4-electron reduction (100% H₂O). This only became apparent when measuring the reduction of hydrogen peroxide.

The above example (as shown in Figures 5 and 5a) shows that changing the size and/or shape of the three-dimensional structure can lead to the formation of various products of the catalytic process, for example O ₂ is transformed into peroxide or water. This can also be applied to all of the examples below, including but not limited to _N2 to _NH3 , _NO3 to _N2 , and _CO2 to HCOOH.

The selected peak size depends on the product required. The smaller the element sizes, the more efficient the conversion into the final product, and especially where multiple products are possible, into a greater concentration of product with a higher energy content.

It is believed that the vertex and/or peak and/or edge of the structure (functional surface) is one of the most important factors determining the activity of the electrocatalyst. It is believed that the apex cross section and/or peak size can be used to select the desired oxidation-reduction product. In general, the narrower, smaller or sharper the angle of the apex or apexes (or ridges) and/or peak, the greater the focusing of current and voltage, and the higher the catalytic turnover.

Conclusion : The surface topography of the electrocatalyst leads to a dramatic change in the reaction mechanism.

Example 4: Electrocatalytic CO Reduction ₂

Objective: To demonstrate the diversity of nanoscale electrocatalysis through CO ₂ reduction.

Method: A three-electrode system with a nanostructured surface of Au as the working electrode, Pt as the counter electrode, and Ag/AgCl as the reference electrode was used. The solution was first degassed by purging with argon gas, and background measurements were taken using cyclic voltammetry. CO ₂ was then introduced by vigorous bubbling and the CO ₂ reduction activity was measured by cyclic voltammetry.

Result: The results are shown in Fig. 6. In FIG. 6, when _CO2 was introduced, a significant current was observed, leading to the formation of CO and methanol.

Conclusion: The electrocatalyst used here demonstrated _CO2 reduction ability.

Example 5: Electrocatalytic O reduction ₂ via Pt

Objective: To demonstrate that the three-dimensionality of a mechanistically efficient electrocatalyst increases catalytic activity by reducing the energy cost (thermodynamics) of the process while increasing its kinetic efficiency.

Method: Pt catalyst (30 nm) was deposited on flat, micropyramidal and nanopyramidal surfaces. A three-electrode system with a platinum (Pt) wire as the counter electrode and Ag/AgCl as the reference electrode was used to measure the _O2 reduction activity on each surface. Cyclic voltammogram was performed on platinum (Pt) coated electrodes. The efficiency of _O2 reduction was then assessed by initial potential (a measure of thermodynamic enhancement) and maximum current (a measure of kinetics).

Results: The results are shown in Fig. 21 for various platinum-coated electrodes: planar, micropyramidal and nanopyramidal at pH 2. The inventors observed a significant shift in the initial potential in the order of planar<micropyramidal<<nanopyramidal surfaces. This trend (flat<micropyramidal<<nanopyramidal) was also observed in the generated relative current.

Conclusion: The surface topography of the electrocatalyst leads to a significant increase in heterogeneous catalysis, both in terms of energy consumption and catalytic kinetics.

Example 6: pH Dependence of Ascorbic Acid, Tafel, Concentration Dependence

Purpose: to demonstrate the generality of potential shifts in different conditions

Method: A three-electrode system with a pyramidal structured surface of Au as the working electrode, Pt as the counter electrode, and Ag/AgCl as the reference electrode was used. Ferrocene was immobilized on both planar and pyramidal electrodes using electrochemical surface modification with differential current distribution. The experiment was carried out in such a way that the surface coverage of ferrocene on both the flat and pyramidal surfaces was comparable (Fig. 7a). Electrochemical conversion of 1 (Fig. 7a and b) and 100 mM sodium ascorbate was carried out in the pH range 1-14.

Results: Ferrocene is known to promote ascorbate oxidation when incorporated into a SAM-modified gold electrode. It is known that the oxidation of ascorbic acid is a process of 2-electron 2-proton oxidation, which results in the formation of one product. As a result, the expected pH shift during oxidation may occur. When ferrocene is added to N3-C11SH/C10SH, the current increases, peaks, and decreases, showing a diffusion-limited process. Similar to hydrogen production and oxygen reduction, an increase in catalytic performance was observed when using a significant voltage reduction required to initiate the oxidation process (Figure 8a). This catalytic enhancement is observed at all pH values.

The Tafel plot clearly showed a reduction in both thermodynamic cost and current exchange density (Fig. 7b).

Conclusion: The 3D shape electrochemically differentiates the activity of the peak from the base, even if they are made of the same material. Catalysis is improved by reducing the energy required for conversion by decreasing the activation energy and increasing the rate of reaction occurring in different media.

Example 7: O Recovery ₂ gold (Au) electrode

Method: A three-electrode system with a pyramidal structured surface of Au as the working electrode, Pt as the counter electrode, and Ag/AgCl as the reference electrode was used. Cyclic voltammetry was carried out on gold electrodes in perchloric acid saturated with _O2 .

Results: The results are shown in Fig. 8 for planar and micropyramidal shapes at pH 1. At this pH Au is known to reduce O ₂ by 4 electrons and 4 protons to water. The introduction of three-dimensionality sharply reduces the initial potential and two peaks are observed: one at low overpotential for the vertex and the other at high overvoltage for the flat regions.

Conclusion: The surface topography of the electrocatalyst leads to a significant increase in heterogeneous catalysis, both in terms of energy consumption and catalytic kinetics (Fig. 8).

Example 8. Mass activity of the catalyst in a steady state.

Purpose: to study the effect of three-dimensionality on the mass activity of the catalyst.

Method: A three-electrode system was used with a pyramidal structure electrodeposited with Pt according to Example 2 on a micropyramidal structure and a flat Au electrode on a 5mm insert for use in a rotating disk electrode. Cyclic voltammogram was performed at 1600 rpm in O2 _- saturated perchloric acid.

Results: A similar thermodynamic shift was observed during O ₂ reduction at 1600 rpm as in the case of a static surface (Fig. 9).

Conclusion: Rotation increases _O2 mass transfer to the electrode and minimizes any enhancement produced by the three-dimensional surfaces. Thus, experiments with a rotating disk electrode allowed a direct comparison of the mass activity of flat and three-dimensional surfaces without any influence of diffusion factors.

Example 8b. Catalytic activity of Pt/C with three-dimensionality.

Objective: To explore electrocatalytic enhancement using 3D with existing Pt/C materials

Method: Prepare 10% Pt/C paint according to the previously described procedure. 10 μL of ink was dropped onto flat surfaces and nanopyramidal surfaces. Then O ₂ reduction was carried out in an O ₂ -saturated NaOH solution. Results: A significant enhancement in the catalytic activity of Pt/C was observed in the case of the 3D platform (Figure 10) compared to the flat surface.

Conclusion: 3D can be used to improve the catalytic performance of existing materials.

Example 9: Converting Nitrate to Nitrogen

Goal: Apply catalytic 3D surface for nitrate reduction

Method: A three-electrode system with a nanopyramidal surface of Au as the working electrode, Pt as the counter electrode, and Ag/AgCl as the reference electrode in PBS buffer was used. Curves were performed with and without the addition of 6 mmol sodium nitrate.

Results: After sodium nitrate was added to the solution, the curve showed a peak at approximately -0.85 mV vs. Ag/AgCl (Figure 11). Holding the voltage at -0.8 mV resulted in the release of an odorless gas thought to be nitrogen.

Conclusion: The curve clearly shows a peak corresponding to nitrate reduction. The exact identity of the gas produced has yet to be determined, but the fact that it is odorless rules out the formation of ammonia and supports the production of nitrogen.

Example 10. Increasing the kinetics of electron transfer to ferrocene through a monolayer

Objective: To demonstrate enhanced electron transfer (KET) kinetics to immobilized ferrocene SAM on a 3D surface compared to a flat one.

Method: A mixed self-assembled monolayer (SAM) with equal molar composition consisting of 1-decanethiol and azide-terminated monolayer with carbon chain 11 was formed on a flat and pyramidal surface with gold sputtering. A three-electrode system with a platinum (Pt) wire as the counter electrode and Ag/AgCl as the reference electrode was used to attach ferrocene to the surface using chronoamperometry. Cyclic voltammograms were performed on the electrodes at different scanning speeds to evaluate the electron transfer mechanism on flat and pyramidal surfaces.

Results: The results are shown in Fig. 12 for pyramidal (a) and flat (b) surfaces at neutral pH. The inventors observed faster electron transfer using the pyramidal surface, as evidenced by a smaller difference in the separation of oxidation and reduction peaks depending on the scan speed (Fig. 13). The results demonstrate an easier transfer of electrons between the chemical and the microstructured electrode surface, whereas the flat surface showed a slower rate throughout the experiment.

Conclusion: the topography of the electrode surface leads to a significant increase in the kinetics of electron transfer by reducing energy costs.

Example 11: Electrocatalytic _O2 Reduction Using Pt in a Rotating Disc Electrode (RDE) Experiment

Objective: Demonstrate that three-dimensionality provides kinetic enhancement and maintains stable mass transfer conditions using (RDE)

Method: prepared flat and pyramidal electrodes (5 mm disks), as in example 5, where Pt catalyst spraying was used. A three-electrode system with a platinum (Pt) wire as the counter electrode and Ag/AgCl as the reference electrode was used to measure the _O2 reduction activity on each surface by performing cyclic voltammetry at rotation speeds of 400, 900, 1600, 2500, 3600 and 4900 rpm (Fig. 14). The _O2 reduction efficiency was then assessed using the initial potential, maximum current and the Koutecki–Levich equation (Fig. 15).

Results: Results for the platinum (Pt) coated micropyramidal electrode are shown in FIG. 15. The inventors observed a significant shift in the initial potential with increasing rotation speed, accompanied by high current for both surfaces due to the decrease in mass transfer in the system. The Koutecki-Levich equation shows a similar curve with a higher degree of electron transfer exhibited by pyramidal electrodes.

Conclusion: Electrocatalyst surface topography results in significant enhancement of heterogeneous catalysis both in terms of energy cost and catalytic kinetics using a 3D pyramidal electrode.

Example 12: Representative Fabrication of a 3D Gold Coated Polycarbonate Matrix (FIG. 16)

The inverted pyramidal array was converted into a silicon (Si) wafer by modifying a previously described anisotropic wet etching method. In this example, inverted pyramidal array microstructures were fabricated in three steps using silicon nitride (Si ₃ N ₄ ) coated silicon (FIG. 16): photolithography was used to determine the pyramid base (50 µm x 50 µm) and distance (75 µm from vertex to vertex), isotropic etching of the Si3N4 layer using buffered hydrofluoric acid followed by anisotropic etching of Si using potassium hydroxide (KOH) solution. Anisotropic etching using an alkaline etchant (30% KOH) results in the formation of a matrix of inverted pyramidal microstructures at an angle of 54.7°. This angle depends on the orientation of the crystal plane and differs for different materials. It should be noted that obtaining a controlled etch rate over a large area is difficult, and reproducibility was low due to the complex parameters of wet etching.

A polished Si [100] plate coated with Si3N4 (resistivity 4-7 Ohm cm) was cleaned with isopropanol. The negative photoresist AZ nLOF 2070 was then spin-coated onto the wafer at 3000 rpm to obtain a thickness of 6.5 μm. The photoresist was then heated at 110 °C on a heating plate for 60 seconds. After cooling to room temperature, the substrate was then transferred to the alignment machine (model) and exposed to ultraviolet light (180 mJ/cm ² ) through a square matrix mask to determine the size and spacing of the inverted matrix. The substrate was then reheated at 110 °C for 60 seconds. After cooling to room temperature, the photoresist was developed by exposing it to AZ326 MIF for 60 seconds. The surface was then washed with deionized water and dried under a stream of nitrogen. The integrity of the lithography process was then examined using an optical microscope after an additional 5 min of curing at 140 °C.

The photoresist pattern was etched onto the Si ₃ N ₄ layer using a buffered hydrogen fluoride solution for 8 hours to minimize excessive etching. The plate was then washed with copious amounts of deionized water. The residual photoresist was then removed with acetone, washed with deionized water, and dried under a stream of nitrogen. The microstructures of the inverted pyramidal matrix were then etched through the Si3N4 mask by anisotropic etching. This was achieved by immersing the plate in a mixture of 30% aqueous KOH with 16% isopropanol at 70 ºC for 75 minutes with constant stirring at 300 rpm. Under these conditions, the Si substrate was etched at a rate of ~60 μm/hour. The plate was then washed with copious amounts of deionized water and dried under a stream of nitrogen before examination under a scanning electron microscope (SEM) (Fig. 17a).

A nickel (Ni) inverted pyramid die stamp was prepared by two successive electroforming cycles of a Si master using a previously described technique. The first inversion was performed by sputtering a thin layer of Ni (100 nm) onto an inverted pyramidal array of Si reference (3 mTorr under argon at 200 W, for 180 seconds). The nickel coated substrate was then immediately immersed in a nickel sulfamate solution containing nickel chloride. Then a constant current of 2.7 A was passed between the Ni-coated Si cathode (0.015 cm ² ) and the Ni anode for 12 hours at 55 °C. During electroforming, the cathode (Ni-coated Si standard) was rotated at a speed of 60 rpm to ensure uniform and continuous electrodeposition. When the thickness of the Ni pyramidal matrix reached ~350 μm, the power supply was turned off and the electroformed Ni was separated from the Si reference, washed with copious amounts of water, and dried under a stream of nitrogen. The Ni pyramidal matrix was then examined by SEM and a second Ni to Ni inversion was performed by repeating the electroforming process described above to produce an inverted Ni pyramidal matrix stamp (Fig. 17b).

The Ni inverted pyramid die stamp was pressed into the polycarbonate using a hot stamping machine (customized model YPL-NIL-SI402, Wu Xi Imprint Nano Tech. Ltd.). A sheet of PC (0.5 mm thick) was placed on top of the nickel die, which was then sandwiched between two polished stainless steel plates and placed in the embossing chamber with the heater facing the Ni side of the stack. Embossing was carried out in vacuum (1.5 × 102 Pa) at 220 °C and a pressure of 1.5 MPa/ ^cm2 for 15 minutes. The substrate was then cooled to room temperature and the embossed polycarbonate was peeled off and examined under an optical microscope. The polycarbonate substrate was then immediately coated with gold by DC magnetron sputtering (Torus Sputtering Machine, Kurt J. Lesker) under 3 mTorr argon at 200 W for 180 seconds, rotating to ensure uniform deposition to produce a thickness of ∼60 nm (Fig. 17c).

Example 13. Hydrogen evolution by Pt particles on flat and three-dimensional electrodes

Objective: Demonstrate that three-dimensionality improves the catalytic performance of a peak-topped catalyst.

Method: K ₂ (PtCl ₄ ) (6 millimolar) in PBS buffer was electrochemically deposited onto both flat and SAM-coated 3D electrodes using chronoamperometry at -0.4 V versus Ag/AgCl.

Results: Using this method, Pt was deposited as particulates on both the planar and three-dimensional electrodes (see Table 2). For planar electrodes, the particles were relatively uniformly distributed over the entire electrode surface, whereas for three-dimensional electrodes, Pt particles were located exclusively at the tops and peaks of the ridges. Table 2 details the parameters of the Pt-coated electrodes and the current densities achieved for the reduction of water to produce hydrogen.

Conclusion: The results show that Pt particles located at the top of the peaks were more than 100 times more active due to the location at the top. The large difference in current density across the platinum area shows that the activity of a platinum molecule on a structure is 130 times greater than the activity of the same platinum molecule on a flat electrode. The current density can be equated to the activity of the catalyst and the rate of hydrogen production.

The data in Table 2 refers to micron-sized pyramids; nano-sized pyramids give significantly greater turnover.

Table 2. Pt particles on a flat surface and Pt particles on peaks

Pt NP on flat surface Pt NP on pyramids See fig. 25 See fig. 26 Particles/(100µm) ² 1540 160 Average particle size (µm) 0.6 0.2 Average surface area of Pt, µm ² 0.7 0.063 Total surface area Pt/(100 µm) ² 1300 10.0 Current density (mA/ ^cm2 ) 48 56.17 Current density/area Pt 0.04 5.6

Example 14: Converting Nitrogen to Ammonia

Goal: Apply catalytic 3D surface for nitrogen reduction

Method: A three-electrode system with a nanopyramidal surface of Au as the working electrode, Pt as the counter electrode, and Ag/AgCl as the reference electrode in PBS buffer was used. Curves were performed with and without the addition of nitrogen to the solution.

Results: After adding nitrogen gas, a clear but reversible deviation in the curve was noticed, as shown in FIG. 19. This was thought to correspond to the formation of ammonia, as evidenced by the appearance of a peak at 420 nm in the UV-visible spectrum.

Conclusion: The curve clearly shows a peak corresponding to nitrogen reduction. The exact identity of all products has not yet been fully confirmed, but the appearance of a peak in the UV-visible region supports the formation of ammonia.

Example 15: Hydrogen Gas Evolution on Planar and 3D Electrodes

Goal: To demonstrate that 3D structures produce more gas than flat structures and that the smaller the structure, the higher the performance. In addition, the 3D structures create bubbles that are effectively and continuously removed from the surfaces of the 3D electrodes, and the smaller the structure elements, the smaller the bubbles.

Method: K ₂ (PtCl ₄ ) (6 millimolar) in PBS buffer was electrochemically deposited onto both flat and SAM-coated 3D electrodes using chronoamperometry at -0.4 V versus Ag/AgCl. The electrodes were installed in the elements shown in Fig. 18, and allowed comparison of hydrogen production on 50 µm and 250 nm pyramids with a flat electrode.

Results: This setup also allowed us to investigate the rate of bubble formation and the relative size of the bubbles and confirmed that the 3D surfaces effectively remove hydrogen from the peaks and do not interfere with production.

Conclusion: The results showed that 3D surfaces overcome one of the major limitations of hydrogen gas production and effectively remove hydrogen from the surface.

Example 16 Conversion of CO ₂ to CO and formic acid

Goal: Apply catalytic 3D surface for _CO2 reduction

Method: A three-electrode system with a nanopyramidal surface of Au as the working electrode, Pt as the counter electrode, and Ag/AgCl as the reference electrode in PBS buffer was used. Curves were performed with and without the addition of CO ₂ in argon to the solution.

Results: After adding _CO2 gas, a clear but reversible deviation in the curve was noticed, as shown in FIG. 20A. Headspace analysis confirmed that this corresponded to the production of CO and the appearance of a CO-myoglobin complex in the UV-visible region (Fig. 20B) and formic acid at the appearance of a peak at 320 nm in the UV spectrum (Fig. 20C).

Conclusion: The curve clearly shows a peak corresponding to nitrogen reduction. The exact identity of all products has not yet been fully confirmed, but the appearance of a peak in the UV-visible region supports the formation of ammonia.

Example 17 Stability of a Pt-coated nanopyramidal matrix during redox cycling

Objective: To demonstrate the stability of Pt-coated nanopyramidal matrix under long-term catalytic conditions using cyclic voltammetry.

Method: Pt catalyst (30 nm) was sprayed onto nanopyramidal surfaces. A three-electrode system was used with a platinum (Pt) wire as the counter electrode and Ag/AgCl as the reference electrode. The surface was continuously cycled from 200 mV to -300 mV for 500 cycles at 10 mV/s to reduce _O2 in a pH 13 solution.

Results: in Fig. 22 does not show a noticeable deterioration in Pt activity, since the maximum O ₂ reduction current was constant at -300 mV.

Conclusion: Long-term cyclic voltammetry showed no signs of decomposition on the surface. If the catalyst were to decompose, a decrease in the catalytic current would be observed towards the underlying nickel substrate.

Example 18. Stability of a Pt-coated nanopyramidal matrix at constant current

Objective: To demonstrate the stability of Pt-coated nanopyramidal electrode array under long-term catalytic conditions using chronoamperometry.

Method: Pt catalyst (30 nm) was sprayed onto nanopyramidal surfaces. A three-electrode system was used with a platinum (Pt) wire as the counter electrode and Ag/AgCl as the reference electrode. A reduction potential of -150 mV was applied for 2.5 days to continuously reduce _O2 in the pH 13 solution.

Results: in Fig. 23 does not show a noticeable deterioration in Pt activity, since the maximum O ₂ reduction current was constant at -5 mA.

Conclusion: After a long catalytic process, the surface showed no signs of decomposition.

Example 19 Control of Catalyst Deposition

Objective: To demonstrate that 3D structures allow control of the amount of catalyst deposited on the peaks.

Method: Gold layered surface structures were cleaned by reactive ion etching (RIE) with O ₂ plasma (2 min) and immersed in a solution of platinum (IV) chloride (1 mM) in PBS. The growth of Pt meso particles was carried out using a square wave potential as follows: a reduction potential (−500 mV) was used to reduce Pt(II) to Pt(0) at the surface within 15 s, and then an oxidation potential (300 mV) was used at for 15 s to stop the process. This cycle was continued until the desired amount of sedimentary Pt was obtained.

Results: Pt deposition occurred predominantly at or near the top of surface structures, as shown in FIG. 24, for 5 pulses (Fig. 24 A) and 10 pulses (Fig. 24 B). As shown in the figure, the amount of deposited Pt clearly increases in proportion to the number of pulses in and around the peak.

Conclusion: The ability to precisely locate and control the amount of catalyst is critical to minimizing the amount of catalyst material required to be applied to a surface and therefore minimizing the cost of producing a catalyst system.

Without wishing to be limited by theory, it is intended that the invention is based on one or more of the following non-limiting concepts:

Exchange current density

An important kinetic parameter that represents the rate of an electrochemical reaction at equilibrium and determines how quickly the electrochemical reaction can occur. The exchange current density of an electrochemical reaction depends on the reaction and on the electrode surface on which the electrochemical reaction occurs, and is therefore related to the true electrode area and the concentration of the reactant.

3D surfaces have higher exchange current density than a flat electrode

Electron transfer coefficient

Defined as the fraction of electrostatic potential energy that affects the rate of reduction during an electrode reaction:

Three-dimensional surfaces have a higher electron transfer coefficient than flat surfaces.

Activation energy

Reducing the activation energy reduces the energy cost for a given catalytic process, thereby reducing the thermodynamic cost.

A three-dimensional surface has a lower potential than a flat surface

In conclusion, the results

- show that the smaller the peak size, the greater the effect on the peak, both with and without additional catalytic coating.

- The size of the peaks makes them ideal for microfluidic applications for both catalytic separation and recombination of a range of carbon, oxygen and nitrogen species. The microfluidic environment can be expected to increase the reaction rate and overall conversion efficiency.

- Both microfluidic and non-microfluidic conditions can be used to create a cascade of catalytic processes.

Claims (66)

1. A method for catalyzing an electrochemical redox reaction of active particles in a conducting solution, including: a) providing an electrocatalytic matrix containing i) a support substrate; ii) surface structures protruding from the support substrate, the surface structures comprising an electrocatalyst; iii) a functional surface on the electrocatalyst, wherein the functional surface is located at the top of the surface structures and wherein the functional surface is intended to contact active species in the conductive solution; b) immersing the surface structures in the solution and introducing a counter electrode into it; And c) creating a current or voltage between the electrocatalyst and the counter electrode such that the charge density (voltage or current) is focused on the functional surfaces and the active species undergo an oxidation-reduction reaction upon contact with the functional surfaces. 2. The method of claim 1, wherein the surface structure or structures are characterized by one or more of the following: i) equal or different or dissimilar heights from the surface of the supporting substrate, ii) same or different or dissimilar shape geometry in relation to other surface structure or structures, iii) regular or irregular geometry, iv) location at equal or unequal distances from each other, v) same or different or heterogeneous density, vi) a group of a plurality of said surface structures, comprising a plurality of surface structures according to any one of claims. i-v). 3. The method of claim 1 or 2, wherein the surface structures are of uniform size and substantially the same geometry. 4. Method according to any one of paragraphs. 1-3, in which the surface structures are made of the same material as the supporting substrate. 5. Method according to any one of paragraphs. 1-4, in which the surface structures are integral with the supporting substrate. 6. Method according to any one of paragraphs. 1-4, in which the catalyst is applied to the top surface of the surface structures and is a material other than the surface structure. 7. The method according to claim 6, in which the electrocatalyst is deposited on the tops of the surface structure. 8. The method of claim 6 or 7, wherein the electrocatalyst is applied to less than about 50% to about 0.000001% of the surface of the matrix as viewed from above. 9. Method according to any one of paragraphs. 1-8, in which the redox reaction is a process with 2 or more electrons, or in which the redox reaction is a process with 4 or more electrons, or in which the redox reaction is a process with 6 or more electrons, or in which the redox reaction is a process with 8 or more electrons. 10. Method according to any one of paragraphs. 1-9, wherein the functional surface is at or near the top of the surface structure, and wherein the width of the top of each surface structure is from about 1 nm to about 5000 μm. 11. The method according to claim 1, wherein the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species; wherein the surface structures have a uniform size and edges and/or vertices that contain the catalyst; wherein if surface structures with a uniform size have a micrometer scale, then a first product is obtained, and if surface structures with a uniform size have a nanometer scale, a second product is obtained, wherein the first and second products are different; Moreover, to obtain the second product, a higher order electronic process is required compared to obtaining the first product. 12. The method of claim 11, wherein the width of the micrometer-scale surface structures at the junction with the support substrate is from about 5 µm to about 500 µm and/or the width of the nanometer-scale surface structures at the junction with the support substrate is from about 25 nm to about 5000 nm. 13. The method according to claim 1, wherein the method catalyzes gas formation, in which the voltage is sufficient to cause multi-electron oxidation or multi-electron reduction of the active species, wherein the surface structures have a uniform size and edges and/or vertices that contain the catalyst; And in this case, the rate of gas formation increases by at least 1.5 times compared to the same electrocatalyst matrix without surface structures of size protruding from the surface of the supporting substrate. 14. Method according to any one of paragraphs. 1-10, in which the redox reaction involves a series of steps without isolating an intermediate. 15. Method according to any one of paragraphs. 1-10, wherein the redox reaction is selected from one or more of the following: release of hydrogen from water; release of oxygen from water; release of hydrogen from protons; oxidation of hydrogen to water; oxidation of hydrogen to hydrogen peroxide; reduction of oxygen to water; reduction of oxygen to hydrogen peroxide; carbon dioxide to carbon monoxide; carbon dioxide to methanol; carbon dioxide to carboxylic acid (eg formic acid); carbon dioxide to aldehyde and/or ketone; carbon dioxide to methane, ethane, propane and/or higher order carbon chains up to C21 _; oxidation of methane to methanol; nitrogen to hydrazine; nitrogen to ammonia; splitting ammonia into hydrogen and nitrogen; methane to methanol; nitrate to nitrogen; nitrate to ammonia. 16. Method according to any one of paragraphs. 1-15, in which the electrocatalyst is suspended in a matrix surrounding peaks of surface structures. 17. Method according to any one of paragraphs. 1-16, wherein the catalyst contains a transition metal, an alloy, an organometallic complex, an organometallic complex containing a transition metal, an organic material that can be oxidized or reduced. 18. Method according to any one of paragraphs. 1-17, in which the sizes of uniformly sized surface structures are selected to vary the resulting redox reaction product. 19. Method according to any one of paragraphs. 1-18, wherein if the structures are on a micrometer scale, a first product or product ratio is obtained, and if the surface structures are on a nanometer scale, a second product or product ratio is obtained, wherein the first and second products and product ratios are different. 20. Method according to any one of paragraphs. 1-19, in which the production of the second product requires a higher order electronic process compared to the production of the first product. 21. Method according to any one of paragraphs. 1-20, wherein the electrocatalyst contains a transition metal, an alloy, an organometallic complex, an organometallic complex containing a transition metal, an organic material that can be oxidized or reduced. 22. Method according to any one of paragraphs. 1-21, in which the method allows the replacement of a cheaper catalyst with lower activity without loss of efficiency. 23. Method according to any one of paragraphs. 1-22, in which the active particles undergo electrochemical modification after contact with the functional surface, and the thermodynamic efficiency and kinetic efficiency of the electrochemical modification are improved compared to the corresponding planar electrode. 24. Method according to any one of paragraphs. 1-23, in which electrochemical activation of the catalyst occurs on the functional surface at a significantly higher rate than elsewhere on the surface on the electrocatalyst layer. 25. Method according to any one of paragraphs. 1-24, which reduces the energy required to carry out a catalytic redox reaction compared to a similar planar electrocatalyst. 26. Method according to any one of paragraphs. 1-25, wherein the width or length of the nanometer-scale surface structures at the junction with the support substrate is from about 25 nm to about 5000 nm, or the width or length of the micrometer-scale surface structures at the junction with the support substrate is from about 5 μm up to about 500 microns. 27. The method of claim 26, wherein the energy required to carry out the catalytic redox reaction is reduced in the method if the surface structures are on a nanometer scale compared to the method if the surface structures are on a micrometer scale.