KR20190129369A - Electrode containing carrier and catalyst - Google Patents

Abstract

The present invention relates to an electrode of an electrochemical cell used when decomposing carbon dioxide and reducing the same into a useful convertible material. According to the present invention, the electrode comprises: first carrier particles; second carrier particles smaller in size than a first carrier; a membrane supporting the first carrier particles and the second carrier particles; and a composite catalyst located on the surfaces of the first carrier particles and the second carrier particles, and comprising catalyst particles of metal components and catalyst particles of metal oxide or metal nitride components.

Description

Electrode with Carrier and Catalyst {ELECTRODE CONTAINING CARRIER AND CATALYST}

The present invention relates to a support and catalyst for use in the electrodes of electrochemical cells used to decompose carbon dioxide and reduce it to useful conversions.

As the industry develops, energy consumption continues to increase, and most of the energy used is mainly hydrocarbons, including fossil fuels. Hydrocarbons basically contain a certain percentage of carbon and hydrogen, so they will produce carbon dioxide when they are burned.

Carbon dioxide is known to be a major cause of global warming. Accordingly, the reduction of carbon dioxide has emerged as a very important issue worldwide.

On the other hand, there are many industrial plants, chemical plants, steel mills, and cement plants in Korea, and these facilities emit a lot of carbon dioxide.

Recently, as a method of removing the generated carbon dioxide, the conversion technology that converts energy into carbon dioxide and useful resources such as oxygen has attracted great attention. Such a conversion technique may use a method of applying pressure at a high temperature or using a catalyst.

Among these conversion techniques, the method of using a catalyst has many advantages that the apparatus and the method itself are very simple, can use electricity produced from renewable energy as it is, and it is very easy to scale up to a commercial scale. . In addition, the method using the catalyst has the advantage that it can selectively produce a variety of carbon compounds.

On the other hand, in order for the method using the catalyst to be put into practical use, it is necessary to be able to stably and continuously produce useful hydrocarbons of C2 or more such as ethylene, ethanol, propanol and butanol having excellent practicality.

Recently, some catalysts such as Cu and Cu ₂ O have been reported to have an effect on the generation of hydrocarbons of C2 or more have attracted attention.

However, in the case of these Cu and Cu ₂ O catalysts, it is difficult to continuously reduce the carbon dioxide, thereby resulting in a problem of low current density and low C2 hydrocarbon production rate.

The problems with these catalysts are all due to the fact that the surface area of the catalyst is small.

Specifically, Cu is used in the form of a two-dimensional electrode such as Cu foil, and Cu ₂ O catalyst is usually used in a form supported on carbon such as Vulcan.

In the case of catalysts having such shapes, the supply of reactants and the discharge of products are not easy, and as a result, the diffusion resistance between the reactants and the products is increased, resulting in lower current density and lower hydrocarbon production rate. Furthermore, when the release of reactants and products from the catalyst is not easy, overvoltage due to diffusion resistance is formed in the electrochemical cell, and the durability of the catalyst and the electrode is reduced due to poisoning of the catalyst material, thereby shortening the lifespan. .

On the other hand, carbon dioxide, one of the reactants, was conventionally supplied mainly in a dissolved state in a liquid. In this case, the solubility of carbon dioxide in the liquid is so low that the current density of the electrochemical cell for carbon dioxide decomposition is lowered and the supply of fuel, i.e., the reactant, is limited.

Therefore, in order to solve the drawbacks of the conventional liquid phase reduction reaction, the conversion efficiency of C2 or more hydrocarbons should be increased by supplying fuel, that is, reactants to the gas phase, and proceeding the carbon dioxide reduction reaction.

However, conventional catalysts, that is, catalysts in the form of Cu foil or catalysts immersed in Vulcan carbon, are not suitable for the reduction reaction due to structural limitations, and thus are not suitable for the reduction reaction and further increase the catalyst surface area. There was a fundamentally limited problem.

Therefore, the present invention intends to invent a catalyst having a high and efficient conversion of carbon dioxide to C2 or more hydrocarbons because the surface area of carbon dioxide can be stably and uniformly proceeded.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode having a novel structure in which an electrode of an electrochemical cell can continuously and smoothly proceed with supply of a reactant and withdrawal of a product.

The electrode of the present invention has a pore which can shorten the pathway of the carbon dioxide source gas, one of the reactants and the generated gas and liquid, and dramatically increase the surface area of the catalyst, which is a region where a reduction reaction occurs. It is an object to provide an electrode which can be used.

The present invention also provides an electrode having an increased surface area and a shorter path of travel, thereby preventing poisoning in the catalyst to improve the durability of the catalyst and the electrode and to suppress overvoltage formation in the entire electrochemical cell. The purpose.

In order to control the pore size between the carrier particles and increase the catalyst surface area to shorten the pathway of the reactants and products, the supply of the reactants and the discharge of the products are smooth. According to the first carrier particles; Second carrier particles smaller in size than the first carrier; A membrane supporting the first carrier particle and the second carrier particle; And a composite catalyst positioned on the surfaces of the first and second carrier particles and including a catalyst particle of a metal component and a catalyst particle of a metal oxide or metal nitride component. Can be.

Preferably, the first carrier particles may have a spherical shape or a hollow shape or a spherical shape having protrusions formed on a surface thereof. The electrode may be provided.

At this time, the equivalent diameter of the second carrier particles, is the first bearing member 20 to 80% of the diameter of the particle preparation; can be provided with electrodes, characterized by (the sizes of all particles based on the D ₅₀ Shall be)

Furthermore, the equivalent diameter of the second carrier particle is 28 to 72% of the diameter of the first carrier particle; an electrode may be provided.

Preferably, the content of the second carrier particles is a ratio of 5 to 20 wt.% Relative to the first carrier particles; may be provided with an electrode.

Preferably, the size of the first carrier particles is 50 nm to 50 ㎛; an electrode may be provided.

Preferably, the first carrier particle and the second carrier particle is one of carbon, metal or conductive oxide; may be provided with an electrode.

Preferably, the catalyst particles of the metal component is Cu, the catalyst particles of the metal oxide or metal nitride component is Cu ₂ O; electrode may be provided.

In this case, the Cu may have a {100} preferred orientation on the surface of the particle; an electrode may be provided.

Preferably, the catalyst particles of the metal oxide or metal nitride component are Cu, Ta, Os, Nb, Mo, Ir, Ag, V, Ru, Mn, Rh, Pd, Ni, Co, Fe, Cr, Hf, Ti , Y, Zr, or an oxide or nitride containing one or two or more of the Sc; an electrode can be provided.

Preferably, the catalyst particles of the metal component is one of Ag, Ni, Au, Pt, Ti, Zn, Cd or an alloy containing these metals; may be provided with an electrode.

Preferably, the content of the complex catalyst may include 1 to 60 wt.% Of the total carrier; an electrode may be provided.

Preferably, the surface of the multi-catalyst particles may include a functional group capable of inducing a carbon surface reactant; an electrode may be provided.

According to the electrode of the present invention, by applying the carrier to the electrode structure it is possible to control the pore size is shortened the path (pathway) of the reactants and products can be smoothly the supply of the reactants and the discharge of the product can be made smoothly.

This can reduce the diffusion resistance on the electrode surface and suppress the poisoning of the catalyst to improve the durability of the catalyst and the electrode.

In addition, it is possible to suppress the formation of overvoltage in an electrochemical cell that reductively decomposes carbon dioxide and further improve the production efficiency of hydrocarbons of C2 or higher.

The electrode of the present invention can significantly increase the surface area of the catalyst by applying a support having pores, and can significantly reduce the amount of the catalyst used.

This improves the activity of the catalyst can greatly improve the production efficiency of C2 or more hydrocarbons.

1 is a schematic diagram of a typical electrochemical cell for decomposing and reducing carbon dioxide.
FIG. 2 shows the ratio of hydrocarbons generated when carbon dioxide is decomposed on the surface of a copper oxide catalyst composed of Cu and Cu (Cu ₂ O) having an oxidation number of +1.
FIG. 3 shows the free energy state at the interface according to the crystallographic orientation of the surface of Cu when generating C2 or more hydrocarbons using a Cu catalyst.
FIG. 4 shows the energy at the transition stage, which is necessary for the formation of C2 or more hydrocarbons on the surface of Cu and / or Cu ₂ O that can be used as a catalyst, with a potential of -0.9 V based on a standard hydrogen reduction potential externally. The energy levels at the level and final stage are shown.
FIG. 5 illustrates in more detail the structure of an electrochemical cell for decomposing carbon dioxide as shown in FIG. 1 and a cathode used in the cell.
6 is a diagram schematically illustrating a catalyst supported on a conventional two-dimensional support.
7 is a diagram schematically showing a catalyst supported on a three-dimensional support in the present invention.
8 is a TEM image showing the microstructure of the Cu ₂ O and Cu nanoparticles prepared in the present invention (where the scale bar is 100nm).

Hereinafter, an electrode including a carrier and a catalyst according to a preferred embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

The present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only this embodiment to make the disclosure of the present invention complete and to those skilled in the art to fully understand the scope of the invention It is provided to inform you.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and like reference numerals designate like elements throughout the specification. In addition, some embodiments of the invention will be described in detail with reference to exemplary drawings. In adding reference numerals to components of each drawing, the same components may have the same reference numerals as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) can be used. These terms are only to distinguish the components from other components, and the terms are not limited in nature, order, order or number of the components. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but between components It is to be understood that the elements may be "interposed" or each component may be "connected", "coupled" or "connected" through other components.

In addition, in the implementation of the present invention may be described by subdividing the components for convenience of description, these components may be implemented in one device or module, or one component is a plurality of devices or modules It can also be implemented separately.

1 is a schematic diagram of a typical electrochemical cell for decomposing and reducing carbon dioxide.

As shown in FIG. 1, the electrochemical cell includes a cathode for receiving an oxidation reaction in which oxygen is generated and a cathode for reducing carbon dioxide, a compartment for accommodating an electrolyte containing the anode and the cathode, and Included are membranes positioned between the cathodes and selectively passing only the desired components on the electrolyte.

On the other hand, although not shown in Figure 1, the cell includes an energy supply source for supplying energy from the outside to drive the cell. The apparatus further includes an extractor for extracting a by-product generated from the reduction of the carbon dioxide. In addition, an electrolyte supply device can be added as needed.

Apart from this, if the by-product resulting from the reduction of carbon dioxide requires another additional reaction, it may optionally also comprise a secondary reactor for the reaction.

When the carbon dioxide is decomposed and reduced in the cell as shown in FIG. 1, it is known that various by-products (or conversion products or products) are produced depending on the type of catalyst in which the reduction reaction occurs.

For example, when Ag or Sb is used as a catalyst, in this case, carbon dioxide reduced in the catalyst generates carbon monoxide through the following reaction formula (1). On the other hand, when Cu and / or Cu ₂ O is used as the catalyst, carbon dioxide is known to generate resources such as methane, ethane, and ethylene through the following reaction formulas (2) to (5).

_{^{CO 2 + 2H + + 2e -}} → CO + H 2 O ... … … … … … -0.51 V (1)

_{^{CO 2 + 8H + + 8e -}} → CH 4 + 2H 2 O ... … … … … -0.24 V (2)

_{^{2CO 2 + 12H + + 12e -}} → C 2 H 4 + 4H 2 O ... … … -0.33 V (3)

_{^{2CO 2 + 12H + + 12e -}} → C 2 H 5 OH + 3H 2 O ... … -0.32 V (4)

_{^{3CO 2 + 18H + + 18e -}} → C 3 H 7 OH + 5H 2 O ... … -0.31 V (V vs. NHE) (5)

On the other hand, in the oxidation electrode, water is oxidized through the following equation (6) to generate oxygen, hydrogen ions, and electrons.

_{n / 2 H 2 O → nH} + + n / 4O 2 + ne - (6)

Therefore, using catalysts containing Cu or +1 -valent Cu ions, not only can various hydrocarbons be obtained, but also more than C2 useful hydrocarbons such as ethylene, ethanol, propanol and butanol.

FIG. 2 shows the ratio of hydrocarbons generated when carbon dioxide is decomposed on the surface of a copper oxide catalyst composed of Cu and Cu (Cu ₂ O) having an oxidation number of +1.

As shown in FIG. 2, when Cu in a metal state is used as a catalyst, CH ₄ and C ₂ H ₄ are mainly generated by reduction of carbon dioxide on the surface of the Cu catalyst. At this time, the production rates of CH ₄ and C ₂ H ₄ are similar to each other, but it can be seen that CH ₄ occupies more fraction than C ₂ H ₄ .

In contrast, if Cu is used as the catalyst, the reduction of carbon dioxide mainly produces CH ₄ and C ₂ H ₄ , but the proportion of hydrocarbons produced is C ₂ H. ₄ it can be seen that accounts for much more than 15 times higher than the maximum percentage of CH _4. This means that the use of Cu having an oxidation number of +1 as the catalyst of the electrochemical cell for carbon dioxide reduction has a very advantageous effect on the generation of hydrocarbons of C2 or more.

However, in the case of a catalyst made of Cu in the metal state, there is a characteristic that the proportion of hydrocarbons produced also varies depending on the orientation on the surface of the catalyst. This means that, in the case of Cu catalyst, controlling the orientation of the surface can further increase the production of hydrocarbons of C2 or higher.

FIG. 3 shows the free energy state at the interface according to the crystallographic orientation of the surface of Cu when generating C2 or more hydrocarbons using a Cu catalyst.

As shown in FIG. 3, the Cu catalyst, although chemically identical, has a lower orientation of the crystal plane in terms of the orientation or orientation of the particles in the direction of the {100} plane than in the {111} plane for all C2 hydrocarbon production. It was investigated to maintain energy state.

For example, to generate a hydrocarbon called "+ OCCHO", it can be seen from FIG. 3 that in the {111} aspect, the free energy of the entire system after the "+ OCCHO" generation reaction increases rather than the state of combining two carbon monoxides. The results of FIG. 3 indicate that in order to generate "+ OCCHO" hydrocarbons from carbon monoxide, energy must be applied externally to compensate for the thermodynamically high energy of the final "+ OCCHO" hydrocarbons, in addition to the generation or conversion This means that energy must be supplied externally to overcome the activation step for the reaction.

On the contrary, in the case of {100}, the state where two carbon monoxides are bonded and the free energy state of the hydrocarbon "+ OCCHO" are almost identical. In addition, the activation energy of the {100} plane was lower than the activation energy of the {111} plane.

This result means that the {100} plane can form thermodynamically stable "+ OCCHO" hydrocarbons with less energy than the {111} plane in terms of crystallography on the surface of the Cu catalyst. In addition, the activation energy for causing the production or conversion reaction also means that less {100} plane is needed.

On the other hand, Figure 4 shows the energy at the transition stage, which is necessary for the formation of C2 or more hydrocarbons on the surface of Cu and / or Cu ₂ O that can be used as a catalyst, with an external potential of -0.9 V based on the standard hydrogen reduction potential The energy levels at the level and final stage are shown.

First, in the case of the Cu metal catalyst having the {111} plane, for the C2 hydrocarbon-forming dimerization called OCCO by combining CO (carbon monoxide) and CO, the adsorbed CO molecules are tilted and then two CO After a transition stage leading the molecules closer together, a surface species called OCCO is created. Compared with the two initial CO molecular stages, there is a difference of free energy of 1.1 eV in the transition stage and 0.86 eV in the final stage. The physical meaning of this free energy difference is that in the case of the Cu metal catalyst having the {111} plane, for dimerization by the combination of CO and CO, an energy of 1.1 eV or more must be supplied from the outside. It means there is an energy barrier that can arise.

On the other hand, in the case of the composite catalyst in which the metal oxide of Cu ₂ O and the Cu metal having the {100} surface coexist, the C 2 hydrocarbon-forming dimerization reaction in which the CO atoms in the Cu atoms and the CO atoms in the + 1-valent Cu ions are OCCO This results in a difference of free energy of 0.71 eV in the transition stage and 0.12 eV in the final stage. This means that in a catalyst in which a metal oxide of Cu ₂ O and a Cu metal catalyst having a {100} surface coexist, the reaction may occur only when externally supplying energy of 0.71 eV or more.

The reason why CC coupling occurs more energetically in the complex catalyst of the Cu ₂ O metal oxide and the Cu metal is that C in the CO adsorbed on the + monovalent Cu ions is positively charged, while Cu atoms This is because C in CO adsorbed at is negatively charged. Thus, due to the electrostatic attraction for the formation of CC bonds between the two Cs, CC coupling occurs more energetically in the complex catalyst of Cu ₂ O metal oxide and Cu metal. This means that for the C2 dimerization reaction, the electrostatic attraction increases the kinetics or thermodynamics driving force.

Accordingly, the present invention includes a Cu metal catalyst having a new structure that controls and regulates the crystallographic orientation of a conventional Cu metal catalyst together with a Cu ₂ O metal oxide catalyst to reduce and convert carbon dioxide to form C 2 or more hydrocarbons with high efficiency. Developed complex catalyst.

Meanwhile, FIG. 5 illustrates in more detail the structure of the electrochemical cell for decomposing carbon dioxide as shown in FIG. 1 and the cathode used in the cell.

As shown in FIG. 5, the negative electrode is first directly or indirectly contacted with an electrolyte to transfer H ⁺ or OH ⁻ ions to the catalyst, a catalyst layer positioned in the middle and supported on a support such as carbon, and involved in the reaction. It consists of a gas diffusion layer that introduces gases into the catalyst and exhausts the formed hydrocarbons.

Conventionally used cathodes are formed by coating the catalyst on the membrane with the catalyst of the catalyst layer pasted or inkized with the ionomer of the same component as the membrane, as shown in the figure below in FIG. 5. Therefore, a conventional cathode used in the prior art, as shown in Figure 5, has a two-layer structure of a membrane electrode assembly (MEA) and a gas diffusion layer (GDL).

H ⁺ or OH ^- ions in the electrolyte and CO ₂ and H ₂ O and electrons present in the gaseous state are moved to the catalyst layer coated on the membrane through a mechanism such as diffusion, and then hydrocarbon products as products in the catalyst layer and Is converted to H ₂ . Afterwards, hydrocarbons and H ₂ generated in the catalyst layer again escape out of the cathode through a mechanism such as diffusion.

At this time, the conventional gas diffusion layer (GDL) is designed to be too dense (dense), the reaction gas (reactant) is difficult to reach the catalyst layer has a problem that the reaction efficiency is reduced.

On the contrary, in the case of the conventional membrane structure, the electrolyte and H ⁺ or OH ^- ions were not sufficiently supplied to the coated catalyst layer, which causes a problem of decreasing the reaction efficiency again.

In addition to the above problems, in the conventional catalysts, generated gases such as hydrocarbons and hydrogen may also be difficult to escape from the dense gas diffusion layer or may be contaminated by soot present in the gas diffusion layer.

Previously used catalysts were used in the form of a two-dimensional structure, such as Cu foil, if the catalyst was a metal such as Cu. In contrast, if the catalyst is in the form of particles (powder, powder) such as Cu or Cu ₂ O, a form in which the powders are supported on a two-dimensional flake structure is mainly used. Since the conventional catalysts have a two-dimensional structure, they have a fundamental limit in increasing the surface area in terms of shape.

6 is a diagram schematically illustrating a catalyst supported on a conventional two-dimensional support. As shown in FIG. 6, the conventional catalyst has various problems due to diffusion resistance because a catalyst powder is supported on a Vulcan carbon support, and thus a path necessary for supply of source gas and diffusion of a product is lengthened. In addition, it is also used as a two-dimensional Cu foil has a small surface area problem.

Therefore, in order to further reduce the carbon dioxide efficiency by reducing decomposition of carbon dioxide, the path of mass transfer is shortened to overcome the restrictions on reactant supply and product discharge, and more particularly, in order to maximize the chemical reaction in the case of gas phase reduction reaction. A catalyst with a high specific surface area is essential.

Accordingly, in the present invention, a complex catalyst including a Cu ₂ O metal oxide catalyst is developed together with a support having a large surface area and controlling a pore size and a Cu metal catalyst having a controlled and controlled crystallographic orientation on the surface of the support. It was.

First, the support or support in the catalyst of the present invention comprises a first support (or first support), the first support being spherical or hollow or spherical in shape, and including protrusions on the surface. It is preferable that it is a shape to say.

Furthermore, in the present invention, it is preferable to further include a second carrier (or a second support) in addition to the first carrier.

At this time, the second carrier in the present invention is more preferably different in shape or different in size from the first carrier.

By way of non-limiting example, the second carrier may have a plate shape, a rod, needle, or flake shape.

Furthermore, the second carrier must have a smaller particle size than the first carrier. At this time, the average size of the second carrier (D ₅₀ ) (if the second carrier is not spherical equivalent diameter (equivalent diameter) is preferably 20 to 80% of the diameter of the first carrier. The average size of the two carriers is more preferably 28 to 72%.

The reason for limiting the average size of the second carrier in the present invention is as follows.

First, the first carrier in the present invention has a spherical shape or a shape close to a spherical shape. When the particles of the spherical first carrier are spatially arranged and stacked in a closest packing form, voids cannot be formed between the first carriers.

In order to prevent this, the present invention additionally includes a second carrier. At this time, if the size of the second carrier is too small, the second carrier is positioned without spatial interference in the space between the particles of the first laminated body that is most densely stacked, so that even if the second carrier includes the second carrier There is a problem that it is difficult to form voids between the retardation particles. Therefore, the second carrier particle is located between the particles constituting the first carrier so that the first carrier particles do not form a close adaptation, that is, the voids are formed between the first carrier particles. It must be done.

If the first carrier particles are densely stacked in two dimensions, the first carrier particles are arranged in a triangular lattice in a plane. At this time, the maximum particle size that can penetrate between the first carrier particles is calculated as about 15.5% of the size of the first carrier particles.

On the other hand, particles such as the first and second carriers of the present invention have a statistically normal particle size distribution (as described above, therefore, the size of the particles in the present invention is always based on D ₅₀ ). do.)

Therefore, the second carrier (or the second support) of the present invention has a lower limit of 20% in order to prevent the first carrier (or the first support) from forming a planar dense layer while considering the distribution of particles. It is desirable to have.

On the contrary, when the size of the second support or the second support is similar to that of the first support (or the first support), the second support cannot be distinguished from each other in terms of the lamination effect of the first support and the particles. do. Therefore, it is preferable that the upper limit of the size of the second carrier has 80% of the first carrier.

On the other hand, if the first carrier particles form a two-dimensional closest stacked, the first carrier particles are arranged in a three-dimensional tetrahedral lattice. At this time, the maximum particle size that can penetrate between the first carrier particles is calculated as about 22.5% of the size of the first carrier particles. If the size of the second carrier particle is 15.5 to 22.5% of the size of the first carrier particle, the second carrier particle may destroy the formation of the two-dimensional closest stacked layer of the first carrier particle, but the spatial Forming the (three-dimensional) closest layer becomes indestructible.

Therefore, it is more preferable that the second carrier or the second support in the present invention has a lower limit of 28% so that the first carrier or the first support does not form a spatially dense layer while considering the distribution of particles. Do.

On the contrary, when the size of the second support or the second support is similar to that of the first support or the first support, the second support cannot be distinguished from each other in terms of the lamination effect of the first support and the particles. Therefore, it is more preferable that the upper limit of the size of the second carrier has 72% of the first carrier.

On the other hand, it is preferable that the mixing ratio of the second carrier to the first carrier has a ratio of 5 to 20 wt.% Relative to the first carrier.

If the second carrier is added less than 5 wt.% Relative to the first carrier, the first carrier tends to be most closely stacked, thereby reducing the voids between the carriers excessively.

On the other hand, when the second carrier is added more than 20wt.% Compared to the first carrier, there is a high possibility that a problem that the size of the entire void is reduced.

It is preferable that the particle size which comprises the said 1st support body (or support body) in this invention is 50 nm-50 micrometers.

If the particle size of the first carrier is smaller than 50 nm, the size of the voids formed between the carrier particles is too small, which leads to a long path of the material.

On the other hand, if the particle size of the first carrier is larger than 50 μm, the bonding force between the particles is weakened, thereby causing a weak mechanical strength of the electrode.

On the other hand, the size of the pores located between the carriers of the present invention, based on the maximum size of the pores, it is preferably 30 nm to 1㎛.

If the size of the pores is smaller than 30 nm, the size of the pores formed between the carrier particles is too small, there is a problem that the path of the material is long.

On the other hand, if the size of the pore is larger than 1㎛, there is a problem that the bonding strength between the particles is weakened thereby weakening the mechanical strength of the electrode.

In addition, the porosity (or porosity) of the carrier of the present invention is preferably 10 to 50%.

If the porosity is less than 10%, there is a problem in that the fraction of the voids formed between the carrier particles is too small so that the path of the material is long.

On the other hand, if the porosity is greater than 50%, there is a problem that the bonding strength between the particles constituting the carrier is weakened, thereby weakening the mechanical strength of the electrode.

The carrier in the present invention includes a second carrier having a smaller size and / or different shape than the first carrier as described above. Therefore, in the present invention, since the second carrier is positioned between the first carriers, the carriers may additionally have an advantageous effect in maintaining mechanical strength even at a relatively high porosity of 50%.

It is preferable that the material of the said support body (or support body) in this invention is carbon, a metal, or a conductive oxide.

This is because the catalyst of the present invention is used for electrodes in electrochemical cells, and therefore electrical conductivity is required in terms of materials.

In particular, when the electrical conductivity is high, the series resistance and contact resistance in the electrochemical cell can be minimized only by the electrical conductivity characteristics. In particular, if the electrochemical cell is implemented in large areas, the high electrical conductivity of the catalyst has the additional advantage of reducing or minimizing the electrical losses of the entire cell.

The carrier (or support) of the present invention may be used by coating on a membrane of an electrode comprising the carrier of the present invention. In this case, the membrane of the electrode may be a membrane used for a membrane electrode assembly or a gas diffusion layer as a specific example.

On the other hand, the catalyst coated on the support in the present invention, the mechanical properties and electrical properties including the surface area is in charge of the support, in consideration of the electrochemical reaction with reactants such as carbon dioxide purely without considering the electrical conductivity It can have a degree of freedom in composition that can be selected.

In addition, the use of the support can greatly reduce the amount of catalyst used, there is an advantage that can increase the efficiency of the catalyst and reduce the cost to increase the economics.

As a non-limiting example, it is not necessarily limited to Cu ₂ O effective for C2 or more hydrocarbon generation, and may include other oxides or nitride compounds that can replace the Cu ₂ O catalyst.

Non-limiting examples of other oxides or nitrides in the present invention include Cu, Ta, Os, Nb, Mo, Ir, Ag, V, Ru, Mn, Rh, Pd, Ni, Co, Fe, Cr, Hf, Ti Oxides or nitrides comprising one or more of, Y, Zr, Sc may be applied.

In addition to the metal catalyst of Cu, the catalyst in the present invention may be applied to a metal such as Ag, Ni, Au, Pt, Ti, Zn, Cd or an alloy catalyst containing these metals.

However, as described above with reference to FIGS. 2 and 3, the catalyst in the present invention includes a Cu ₂ O catalyst having a high C2 or higher hydrocarbon production rate and a Cu metal catalyst whose orientation is controlled to have a {100} preferred orientation on the surface thereof. The combined catalyst is more preferable.

In particular, as shown in FIG. 4, in the case of a composite catalyst in which a metal oxide catalyst of Cu ₂ O and a Cu metal having a {111} plane coexist, CC coupling occurs well even at very low energy. This means that, in the case of the composite catalyst of the present invention, C2 or more hydrocarbons are likely to be produced by the promoted C2 dimerization reaction.

However, in the electrode of the present invention, as shown in Figure 7, the catalyst of the above components is located on the surface of the carrier (or support) in the front.

Therefore, if the catalyst in the present invention is a complex catalyst in which a metal oxide catalyst of Cu ₂ O and a Cu metal having a {111} plane coexist, the catalyst of the Cu metal component in the present invention is a particle having a shape other than the conventional Cu foil shape. It should be a Cu ₂ O metal oxide catalyst in shape. Furthermore, the catalyst of the Cu metal component in the present invention must be a particle whose surface has a {100} preferred orientation in order to increase the C2 or higher hydrocarbon production rate.

In the present invention, in order to form a particulate Cu metal catalyst, a Cu metal catalyst having a {100} preferred orientation was produced using the following method.

Specifically, in the Cu metal catalyst particles of the present invention, Cu ₂ O particles were first formed, and then Cu metal particles of cubic shape were produced through a reduction reaction.

Specifically, in order to obtain uniform CuCl nanocrystals, in the present invention, CuCl microparticles are first dissolved in an aqueous hydrochloric acid (HCl) solution having a pH of 0.5, and HCuCl ₂ is synthesized according to the following equation (7) by a complex reaction. Formed.

CuCl + _x HCl ↔ H _x CuCl _{1 + x} (7)

The pH value of the solution then increased to 6.5 by adding pure water. As a result, the reverse reaction (that is, precipitation of CuCl) of Equation (7) proceeded at a very high rate, and uniform CuCl nanocrystals were formed according to fast and uniform nucleation and growth (see FIG. 8 (a), Where the scale bar is 100 nm).

Since the medium has a sufficiently high pH of 6.5, the precipitated CuCl nanocrystals gradually undergo alkaline hydrolysis according to equation (8), resulting in hollow Cu ₂ O nanocrystals.

^{2CuCl + 2OH - = 2Cl - +} Cu 2 O + H 2 O (8)

In order to track the morphological evolution at this stage, the CuCl nano lattice formed rapidly when pure water was added was observed by TEM using a transmission electron microscope (TEM) lattice (grid) of nickel.

In the early stage of hydrolysis (2 minutes), the separated Cu ₂ O nanoparticles form on the surface of the CuCl nanocrystals. The number of Cu ₂ O nanoparticles increases with increasing reaction time, so that the nanoparticles are gradually connected at a reaction time of about 5 minutes.

After 10 minutes of hydrolysis time, CuCl—Cu ₂ O core-shell nanocrystals are found in the final product. At this stage the Cu ₂ O shells appear to be porous (see inset in FIG. 8 (b)).

After 20 minutes of hydrolysis, the form of the product looks like a yolk shell, and the shell becomes denser (Fig. 8 (c)). As expected, a Cu ₂ O diffraction pattern was observed in the selected area diffraction pattern (SADP). This means that this nanocrystal is Cu2O.

After 30 minutes of hydrolysis, hollow Cu ₂ O nanocrystals are formed, some of which show a double shell (FIG. 8 (d)). SADP in the inset of FIG. 8D demonstrates that the hollow nanocrystals are almost pure Cu ₂ O.

As described above, Cu nanocrystals were prepared by heat treatment with a reducing gas such as hydrogen using nanocrystals having undergone hydrolysis for 30 minutes or more.

As shown in FIG. 8, the Cu nanocrystals of the present invention have the same size as several tens of nanometers in size with CuCl or Cu ₂ O nanocrystals, which are precursors, and the crystal orientation of the shell is {100} in terms of shape. It has a cubic shape having a.

The Cu nanocrystals thus obtained may be uniformly coated on a gas diffusion layer (GDL), an ion exchange membrane, and an electrolyte membrane carrier (or support) in the present invention by coating a catalyst slurry such as a spray method or a decal method. have.

At this time, the mixing ratio of the catalyst to the support (or support) in the present invention is preferably 1 to 60 wt.% Of the catalyst relative to the support.

If the proportion of the catalyst is less than 1 wt.%, The content of the catalyst is so small that the efficiency of carbon dioxide reduction and C2 formation at the cathode is too low.

On the other hand, when the ratio of the catalyst is more than 60 wt.%, Even if the support is formed of carbon lighter than the catalyst, the amount of added catalyst is excessively larger than that of the catalyst which can be located on the surface of the support, resulting in an increase in efficiency. There is a problem that the amount of the catalyst lost in the manufacturing process without an increase increases.

Meanwhile, in the present invention, a functional group capable of inducing a carbon surface reactant at the surface of the catalyst may be introduced as necessary. By way of non-limiting example, the surface of the catalyst may be coated or doped with functional groups including components such as S, N, B, and the like.

When such a functional group is coated or doped, the electronic structure of the catalyst may be deformed to affect the activity of the catalyst, and the agglomeration phenomenon of the catalyst that may occur during the reaction by strengthening the bonding force between the support (support) and the catalyst may be caused. There is an advantage that can be prevented.

The electrode of the present invention is capable of controlling the pore size according to the support (or support) size, shape and ratio, and diffusion by smoothly supplying the reactant and the discharge of the product by the catalyst layer coated on the support surface The resistance can be greatly reduced.

Through this electrode configuration having pores, it is possible to form a three-phase interface between the solid electrode and the liquid and gaseous reactants and products, thereby increasing the hydrocarbon generation efficiency of C2 or higher and improving the durability of the catalyst and the electrode. It is expected.

As described above, the present invention has been described with reference to the drawings, but the present invention is not limited to the embodiments and drawings disclosed herein, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is obvious that modifications can be made. In addition, even if the above described embodiments of the present invention while not explicitly described and described the operation and effect according to the configuration of the present invention, it is obvious that the effect predictable by the configuration is also to be recognized.

Claims (13)

First carrier particles;
Second carrier particles smaller in size than the first carrier;
A membrane supporting the first carrier particle and the second carrier particle;
A complex catalyst positioned on the surfaces of the first carrier particles and the second carrier particles and including catalyst particles of a metal component and catalyst particles of a metal oxide or metal nitride component;
Electrode comprising a.
The method of claim 1,
The first carrier particle has a spherical shape or a hollow shape or a spherical shape with protrusions formed on a surface thereof.
Electrode characterized in that.
The method of claim 2,
The equivalent diameter of the second carrier particle is 20 to 80% of the diameter of the first carrier particle;
Electrode characterized in that.
The method of claim 3,
The equivalent diameter of the second carrier particle is 28 to 72% of the diameter of the first carrier particle;
Electrode characterized in that.
The method of claim 1,
The content of the second carrier particle is in a ratio of 5 to 20 wt.% Relative to the first carrier particle;
Electrode characterized in that.
The method of claim 1,
The size of the first carrier particle is 50 nm to 50 μm;
Electrode characterized in that.
The method of claim 1,
The first carrier particle and the second carrier particle are one of carbon, metal or conductive oxide;
Electrode characterized in that.
The method of claim 1,
The catalyst particles of the metal component are Cu, and the catalyst particles of the metal oxide or metal nitride component are Cu ₂ O;
Electrode characterized in that.
The method of claim 8,
Cu has {100} preferred orientation at the particle surface;
Electrode characterized in that.
The method of claim 1,
The catalyst particles of the metal oxide or metal nitride component are Cu, Ta, Os, Nb, Mo, Ir, Ag, V, Ru, Mn, Rh, Pd, Ni, Co, Fe, Cr, Hf, Ti, Y, Zr , An oxide or nitride comprising one or more of Sc;
Electrode characterized in that.
The method of claim 1,
The catalyst particles of the metal component are one of Ag, Ni, Au, Pt, Ti, Zn, Cd or an alloy containing these metals;
Electrode characterized in that.
The method of claim 1,
The content of the complex catalyst is 1 to 60 wt.% Of the total carrier;
Electrode characterized in that.
The method of claim 1,
The surface of the multicatalyst particles comprises a functional group capable of inducing a carbon surface reactant;
Electrode characterized in that.

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