KR20220148753A - Electrochemical electrode including hydrogel protective layer and method for producing gas using same - Google Patents

Abstract

An electrochemical electrode according to the present invention uses a protective layer including a hydrogel to prevent aggregation and desorption even when a particulate catalyst is used, thereby securing stability to realize an electrode with long duration. The present invention includes: a gas generating electrode including a transparent electrode layer and a catalytic material layer; and a hydrogel protective layer covering the gas generating electrode.

Description

Electrochemical electrode including hydrogel protective layer and method for producing gas using same

The present invention relates to an electrochemical electrode having improved stability by preventing aggregation and desorption of a catalyst and preventing photocorrosion of a light absorption layer and a charge transport layer, and a method for producing a gas by using the same for electrolysis.

In order to put solar-powered hydrogen production technology to practical use, solar-to-hydrogen efficiency (STH) of 10% or more and a low cost comparable to the fossil fuel-based hydrogen production unit cost are required. can be broadly divided into three categories. The first is a powder-type photocatalyst-based system, and the highest efficiency reported so far is very low at the level of 1% STH, and it is difficult to separate generated oxygen and hydrogen, making it difficult to put into practical use. Currently, the most mature technology, the photovoltaic-electrolysis (PV-EC) system utilizing the voltage obtained from the solar cell achieved high efficiency of up to 30% of STH, but the high unit cost due to the complex system is an obstacle to practical use. becomes this On the other hand, in the case of a photoelectrode-based photoelectrochemical (PEC) system in which the absorption layer and the catalyst are integrated into one device, the production cost can be lowered by using low-cost materials, and it is considered an intermediate step in terms of efficiency and complexity.

Photoelectrochemical water decomposition is an eco-friendly method that can generate hydrogen energy using water and solar energy. In order to construct an efficient photoelectrochemical system, attempts have been made to increase the efficiency by changing the size and structure of the electrode or synthesizing the catalyst together with the electrode.

In the photoelectrochemical water splitting process, the design of durable electrodes is very important as it plays an important role in determining the cost. However, the reality is that it is very difficult to achieve long-term stability due to corrosion and separation of the constituent materials. Although the stability of the device could be improved to some extent through various strategies such as inserting a functional layer between the catalyst and the protective layer or adjusting the electrolyte composition, the gradual photocurrent degradation is still a problem that cannot be avoided. In addition, in the case of simply using a layered protective film, since it is difficult to transfer ions and materials from the electrolyte to the catalyst, there is still a problem in that the initial current is lowered, so that the increase in driving time is insignificant.

Accordingly, research and development for practical use of the electrochemical electrode is still required.

An object of the present invention is to provide an electrochemical electrode having a long duration by ensuring stability.

Another object of the present invention is to provide an electrochemical electrode capable of physically preventing desorption of a catalyst, which is a major cause of deterioration of electrode stability, and suppressing photocorrosion.

The present invention is a transparent electrode layer; A gas generating electrode including a catalyst material layer positioned on the transparent electrode layer and a hydrogel protective layer covering the gas generating electrode, wherein the hydrogel protective layer is conformally bound on the gas generating electrode An electrochemical electrode is provided.

In the electrochemical electrode according to an embodiment of the present invention, a light absorption layer and a charge transfer layer may be included between the transparent electrode layer and the catalyst material layer.

In the electrochemical electrode according to an embodiment of the present invention, the light absorption layer may be selected from the group consisting of a post-transition metal, a metalloid, and a transition metal.

In the electrochemical electrode according to an embodiment of the present invention, the charge transport layer may be made of a metal or a metal oxide, and the catalyst material layer is a metal and its oxide, nitride, oxynitride, carbide, sulfide, phosphide, and At least one catalyst selected from the group consisting of alloys may be included.

In the electrochemical electrode according to an embodiment of the present invention, the thickness of the hydrogel protective layer may be 10 to 2,000 μm, the pore diameter of the hydrogel protective layer may be 1 to 1,000 nm.

In the electrochemical electrode according to an embodiment of the present invention, the surface of the gas generating electrode may include a first region in which the catalyst material layer is located, and a second region in which the catalyst material layer is not located, The hydrogel protective layer may be covalently bonded to the surface of the gas generating electrode, and the hydrogel protective layer may include a multimer having an electric charge.

In the electrochemical electrode according to an embodiment of the present invention, the hydrogel protective layer may have rigidity and ductility such that when the _rs value is 0.2 mm or less, the P _max /P _f value is 1 or less, (where r _s is the radius of the initial crack of the hydrogel, P _max is the maximum pressure applied to the hydrogel as the bubble expands, and P _f is the critical pressure required for cracking of the hydrogel.) The hydrogel protective layer and The bonding strength of the gas generating electrode may be stronger than P _max .

The present invention comprises the steps of (a) preparing a first liquid containing an alkoxyalcohol-based solvent; (b) preparing a second liquid comprising a mercapto acid-based solvent and an alkanolamine-based solvent; (c) forming a light absorption layer by applying a mixture of the first liquid and the second liquid to the transparent electrode layer; (d) forming a charge transfer layer on the light absorption layer formed in step (c); (e) forming a catalyst material layer on the charge transport layer formed in step (d); and (f) forming a hydrogel protective layer covering the gas generating electrode including the light absorption layer, the charge transfer layer and the catalyst material layer formed in the steps (c) to (e). provides

In the method of manufacturing an electrochemical electrode according to an embodiment of the present invention, the mercapto acid-based solvent is mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptohexanoic acid, mercaptooctanoic acid, mercapto. It may be selected from the group consisting of todecanoic acid and mercaptododecanoic acid, and the alkanolamine-based solvent is NH ₂ -(CH ₂ ) _m -OH (m is an integer of 1 to 4) represented by the formula compound, and the molar ratio of the mercapto acid-based solvent and the alkanolamine-based solvent of the second solution may be 18:1 to 20:1.

In the method of manufacturing an electrochemical electrode according to an embodiment of the present invention, the step (c) may be to coat the mixed solution on a transparent electrode layer and annealed in an inert gas atmosphere, in step (d), The charge transport layer may be formed by atomic layer deposition (ALD). In addition, after step (e), 3-(trimethoxysilyl)propyl methacrylate or alkoxysilaneamine may further comprise the step of modifying the surface of the gas generating electrode, in step (f), the The hydrogel protective layer may be prepared by polymerizing a polymerizable monomer and a polyfunctional monomer including an amine group.

The present invention provides a method for producing a gas selected from the group consisting of hydrogen, oxygen, nitrogen and chlorine using the electrochemical electrode.

The electrochemical electrode according to the present invention secures stability by preventing aggregation and desorption of the catalyst, thereby realizing an electrode with a long duration. In addition, by inducing rapid desorption of air bubbles generated on the surface of the electrochemical electrode, high photocurrent density can be maintained, and photocorrosion phenomenon can be suppressed. The electrochemical electrode according to the present invention can improve the stability by 100 times or more compared to the conventional electrode, thereby dramatically reducing the production cost of the system.

1 is a graph showing electrical characteristics of an electrode when different concentrations of monomers are made.
Figure 2 is a graph showing the stability of the electrode when the concentration of the monomers are different from each other.
3 is a graph showing electrical characteristics of an electrode in a neutral electrolyte (pH 7).
4 is a graph showing electrical characteristics of an electrode in a basic electrolyte (pH 8).
5 is a diagram showing the structure of an electrode immediately after fabrication.
6 is a diagram showing the structure of an electrode that is not coated with a hydrogel protective layer after driving for 5 hours.
7 is a diagram showing the structure of an electrode coated with a hydrogel protective layer after driving for 100 hours.
8 is a diagram illustrating the formation, growth and separation of air bubbles on the surface without a hydrogel protective layer and on the surface of 10% PAAM through a high-speed camera.
9 is a graph evaluating the stability of the electrode when the concentration of the surfactant is changed.
10 is a diagram of observing bubbles immediately before separation after reaching CFR (hydrogel/electrolyte interface).
11 is a diagram observing the surface of the electrode coated with a low-rigidity hydrogel protective layer.
12 is a graph evaluating the stability of an electrode coated with a low stiffness hydrogel protective layer.
13 is a graph evaluating the stability of the electrode when the thickness of the hydrogel protective layer is changed.
14 is a view of the surface of the electrode coated with a hydrogel protective layer having a thickness of 100 μm.
15 is a diagram of observing the surface of the electrode coated with a hydrogel protective layer having a thickness of 200 μm.
16 is a view of the surface of the electrode coated with a hydrogel protective layer having a thickness of 1,200 μm.
17 is a graph evaluating the stability of the electrode when the thickness of the hydrogel protective layer is changed.
18 is a graph evaluating the stability of the electrode when the thickness of the hydrogel protective layer is changed.

Hereinafter, the electrochemical electrode of the present invention and a manufacturing method thereof will be described in detail with reference to the accompanying drawings.

The drawings introduced below are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention.

At this time, if there is no other definition in the technical terms and scientific terms used, it has the meaning commonly understood by those of ordinary skill in the art to which this invention belongs, and in the following description and accompanying drawings, the subject matter of the present invention Description of known functions and configurations that may unnecessarily obscure will be omitted.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

In this specification and the appended claims, terms such as first, second, etc. are used for the purpose of distinguishing one component from another, not in a limiting sense.

In this specification and the appended claims, the terms include or have means that a feature or element described in the specification is present, and unless specifically limited, one or more other features or elements are added. This does not preclude the possibility that it will be.

In this specification and the appended claims, when a part of a film (layer), region, component, etc. is said to be on or on another part, not only when it is directly on top of another part in contact with it, but also another film ( layer), other regions, and other components are also included.

Electrochemical electrode according to the present invention, a transparent electrode layer; A gas generating electrode including a catalyst material layer positioned on the transparent electrode layer and a hydrogel protective layer covering the gas generating electrode, wherein the hydrogel protective layer is conformally bound on the gas generating electrode characterized.

In one embodiment, a light absorption layer and a charge transfer layer may be included between the transparent electrode layer and the catalyst material layer.

In one embodiment, the light absorption layer may include a material selected from the group consisting of a post-transition metal, a metalloid, and a transition metal. The type of the post-transition metal may be selected from the group consisting of Ga, In, Sn, Tl, Pb and Bi, and the type of the metalloid may be selected from the group consisting of Ge, Sb and Te, and the transition metal The type may be selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo. In addition, the light absorption layer may include a chalcogenide or an oxide thereof including a material selected from the group consisting of post-transition metals, metalloids and transition metals. Here, the type of chalcogen may be selected from the group consisting of S (sulfur), Se (selenium), and Te (tellurium). The light absorption layer having a low bandgap energy is very advantageous for absorption of sunlight, particularly absorption of a long wavelength. More specifically, when the bandgap energy is 1.50 eV or less, it is advantageous to absorb sunlight, more preferably 1.40 eV or less, and most preferably, when it is 1.25 eV or less, it is advantageous to absorb sunlight.

In one embodiment, the charge transfer layer may be made of a metal or a metal oxide, preferably the metal or metal oxide may be a Group 4 metal or a Group 4 metal oxide, more preferably the Group 4 metal is It may be Ti (titanium) or Zr (zirconium), and more preferably Ti. Accordingly, the Group 4 metal oxide may be TiO ₂ or ZrO ₂ , preferably TiO ₂ . Here, when TiO ₂ receives light energy corresponding to the band gap, electrons are excited from the valence band (VB) to the conduction band (CB), and a hole is left in the valence band. The holes generated in the valence band form OH radicals on the TiO ₂ surface and react with substrates adsorbed on the catalyst surface to oxidize organic matter. The electrons excited in the conduction band lose their recombination site when the holes return to their original state by oxidation reaction with the substrate adsorbed on the surface of the catalyst, and transfer electrons to neighboring Ti(IV) on the surface or Ti inside the catalyst. It is reduced from 4(IV) valence to 3(III) valence, and in this principle, TiO ₂ can be used as a charge transfer layer of an electrode.

In one embodiment, the catalyst material layer may include at least one catalyst selected from the group consisting of metal and its oxides, nitrides, oxynitrides, carbides, sulfides, phosphides, and alloys, wherein the metal is Pt, Ti, Sn, Zn, Mn, Mg, Ni, W, Co, Fe, Ba, In, Zr, Cu, Al, Bi, Pb, Ag, Cd, Ga, Y, Mo, Rh, Pd, Sb, Cs, It may include at least one of La, V, Si, Al, and Sr. Since the band gap of TiO ₂ is 3.0 to 3.2 eV, light in the ultraviolet region having a wavelength shorter than 388 nm is required to overcome this band gap. However, the ultraviolet region included in the sunlight is only less than 5%, so it is one of the methods for using the light in the visible region that accounts for most of the sunlight. Platinum is used as a material that receives electrons from the conduction band of TiO ₂ . By facilitating electron transport, electron-hole recombination is reduced, thereby improving the overall reaction rate.

In addition, the catalyst material layer may be formed of a catalyst in the form of a thin film or particles, and the catalyst in the form of particles may be 0-dimensional particles or an aggregate of 0-dimensional particles. Here, the particle-form catalyst may have a diameter of 1 to 20 nm, preferably 1 to 10 nm, and more preferably 1 to 5 nm.

In one embodiment, the surface of the charge transport layer may include a first region in which the catalyst material layer is located and a second region in which the catalyst material layer is not located. Accordingly, the hydrogel protective layer may be in contact with the first region in which the catalyst material layer is located, and may be in contact with the second region in which the catalyst material layer is not located. As will be described later, in the first region, the hydrogel protective layer is positioned as a protective layer on the catalyst material layer to stably protect the catalyst of thin films, zero-dimensional particles, or aggregates of zero-dimensional particles, and in the second region, the gas generating electrode can form covalent bonds with the surface of

Here, the first region and the second region preferably have an area ratio of 100:1 to 1:100, more preferably 70:1 to 1:70, and more preferably 40:1 to 1:70. It may be formed in an area ratio of 1:40, and most preferably in an area ratio of 10:1 to 1:10.

In one embodiment, the hydrogel protective layer covering the gas generating electrode may be prepared by polymerizing a polymerizable monomer and a polyfunctional monomer including an amine group. That is, by forming a three-dimensional network structure by cross-linking the polymerizable monomer and the polyfunctional monomer including an amine group, it can be stably coated on the gas generating electrode. The catalyst used for the electrode is preferably used in the form of particles rather than in the form of a thin film. To overcome this disadvantage, the hydrogel protective layer is coated on the gas generating electrode to form a three-dimensional network structure to form a physical bond, as well as to chemically bond by covalent bonding as described below.

The polymerizable monomer for preparing the hydrogel protective layer may be applied without limitation as long as it is a polymerizable monomer including an amine group, and specifically, an acrylamide or methacrylamide monomer may be applied.

The hydrogel protective layer is preferably formed to a thickness of 10 to 2,000 μm, more preferably may be formed to a thickness of 30 to 1,500 μm, and more preferably formed to a thickness of 50 to 1,200 μm. . When the thickness of the hydrogel protective layer is formed to a thickness of 10 to 2,000 μm, the bubbles generated from the gas generating electrode easily escape the hydrogel protective layer, and at the same time, there is no phenomenon in which the bubbles escape and form larger bubbles. It has the advantage of improving stability.

The pores of the hydrogel protective layer are preferably formed with a diameter of 1 to 1,000 nm, more preferably may be formed with a diameter of 2 to 100 nm, and more preferably be formed with a diameter of 3 to 50 nm. It may be formed, more preferably with a diameter of 4 to 40 nm, and more preferably formed with a diameter of 5 to 30 nm. When the pores of the hydrogel protective layer are formed with a diameter in the above range, the network is dense and the bubbles generated in the gas generating electrode easily escape the hydrogel protective layer, thereby improving stability.

The hydrogel protective layer is preferably polymerized from an aqueous monomer solution having a concentration of 8 to 20% by volume, more preferably from an aqueous monomer solution having a concentration of 8 to 16% by volume, and most preferably from 8 to 12% by volume. % concentration of an aqueous monomer solution. When the hydrogel protective layer is polymerized from an aqueous monomer solution having a concentration of 8 to 20% by volume, the bubbles generated from the gas generating electrode easily escape the hydrogel protective layer, and at the same time, the bubbles escape and form larger bubbles. This has the advantage of improving stability.

The hydrogel protective layer is synthesized by crosslinking a monomer and a crosslinking agent. Here, the monomer and the crosslinking agent are preferably included in a molar ratio of 60:1 to 100:1, more preferably in a molar ratio of 70:1 to 90:1, and most preferably 75:1 to 85 It may be included in a molar ratio of :1.

The hydrogel protective layer may be conformally bound on the gas generating electrode. A hydrogel is densely formed along the surface of the gas-generating electrode, and the hydrogel is bound on the gas-generating electrode, thereby preventing the hydrogel from being desorbed from the gas-generating electrode, and at the same time, the bubbles generated in the gas-generating electrode are generated from the hydrogel. There is an advantage in that the gel protective layer easily escapes and the stability of the electrochemical electrode is improved.

In addition, the hydrogel protective layer may be covalently bonded to the surface of the gas generating electrode to form a coating layer. The gas generating electrode may be covalently bonded with a compound having a reactivity on the surface of the gas generating electrode to form a self-assembled monolayer, and may be activated as described below by further including the compound with a reactive functional group have.

Specifically, the compound having reactivity on the surface of the gas generating electrode may be an alkoxysilaneamine compound, and the formula Si(OR) ₃ (CH ₂ ) _p NH ₂ (p is an integer of 1 to 4, R is hydrogen or C ₁ -C ₄ may be a compound represented by a), more specifically (3-aminopropyl) triethoxysilane ((3-aminopropyl) triethoxysilane; APTES).

As the surface of the gas generating electrode forms a self-assembled monolayer with the alkoxysilaneamine compound, an amine group, which is a reactive functional group, may be exposed on the surface, and the amine group may be subsequently activated with an aldehyde group. The amine group can be activated as an aldehyde group by treatment with a compound containing 2 to 4 aldehyde groups for aldehyde group activation. Non-limiting examples of the 2 to 4 aldehyde groups may be glutaraldehyde, but is not limited thereto.

As the aldehyde group and the amine group of the polymerizable monomer constituting the hydrogel protective layer are covalently bonded to each other, the hydrogel protective layer may be stably covalently bonded to the surface of the gas generating electrode. Through the covalent bond as described above, the hydrogel protective layer is selectively covalently bonded to the surface of the gas generating electrode, and since it does not form a covalent bond with the catalyst material layer, rapid desorption of hydrogen bubbles generated on the surface of the catalyst material layer is not achieved. It may be possible, and since the hydrogel protective layer stably protects the catalyst material layer, desorption of the catalyst material layer can be effectively suppressed, which is preferable.

In addition, since the hydrogel protective layer contains a multimer having an electric charge, it is possible to suppress the dissolution of the electrode surface by inhibiting the movement of ions generated by dissolving the elements constituting the gas generating electrode is preferable.

In conclusion, the hydrogel protective layer not only prevents the desorption of the catalyst present on the surface of the gas generating electrode, but also the hydrogel protective layer has a high concentration of dissolved metal ions from the periphery of the coated electrode surface, so the Le Chatelier principle This has the effect of inhibiting the dissolution of additional metal ions.

In one embodiment, as the reaction proceeds in the electrochemical electrode, bubbles are generated, and as the generated bubbles expand, the pressure applied to the hydrogel increases. Here, the maximum pressure (P _max ) applied to the hydrogel as the bubble expands can be calculated by Equation 1 below.

[Equation 1]

(Where r _s is the radius of the initial crack of the hydrogel, E is the elastic modulus of the hydrogel, and γ is the surface energy of the hydrogel (0.072 J/m ² ).)

In addition, the critical pressure required for cracking the hydrogel can be calculated by Equation 2 below.

[Equation 2]

(Where G _c means the critical energy-release ratio of the hydrogel.)

That is, when the pressure applied to the hydrogel protective layer is greater than the critical pressure, the bubbles expand and cracks occur in the hydrogel.

When the _rs value is 0.2 mm or less, the P _max /P _f value may have a stiffness and ductility of 1 or less, and when the P _max /P _f ratio is 1 or more, the hydrogel protective layer is cracked by the generated air bubbles This occurs, and when cracks occur in the hydrogel protective layer, the electrode surface is not protected and damaged, and the current is gradually reduced. Therefore, when the bonding strength between the hydrogel protective layer and the gas generating electrode is stronger than P _max , there is an advantage in that the hydrogel protective layer does not easily detach.

The present invention also provides a method for preparing a gas selected from the group consisting of hydrogen, oxygen, nitrogen and chlorine by irradiating light to the electrochemical electrode.

The method for manufacturing an electrochemical electrode according to the present invention includes the steps of: (a) preparing a first liquid containing an alkoxyalcohol-based solvent; (b) preparing a second liquid comprising a mercapto acid-based solvent and an alkanolamine-based solvent; (c) forming a light absorption layer by applying a mixture of the first liquid and the second liquid to the transparent electrode layer; (d) forming a charge transfer layer on the light absorption layer formed in step (c); (e) forming a catalyst material layer on the charge transport layer formed in step (d); and (f) forming a hydrogel protective layer covering the gas generating electrode including the light absorption layer, the charge transfer layer and the catalyst material layer formed in the steps (c) to (e).

In one embodiment, the first liquid prepared in step (a) may contain an alkoxyalcohol-based solvent as a solvent. Here, the alkoxyalcohol-based solvent may be a solvent selected from 2-methoxyethanol, 2-methoxypropanol, and 3-methoxypropanol. At this time, it is preferable to prepare the first solution at a concentration of 0.02 to 0.4M, more preferably a concentration of 0.04 to 0.3M, more preferably a concentration of 0.06 to 0.2M, and most preferably 0.08 to 0.1M concentration, but is not limited thereto.

In one embodiment, the second liquid prepared in step (b) may contain an alkanolamine-based solvent and a mercapto acid-based solvent as a solvent. Here, the alkanolamine-based solvent may be a compound represented by the formula of NH ₂ -(CH ₂ ) _m -OH (m is an integer of 1 to 4), and preferably NH ₂ -( CH ₂ ) _m -OH (m is an integer of 1 to 4) may be a compound represented by the formula, most preferably may be ethanolamine.

In addition, the mercapto acid-based solvent may be a solvent selected from mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptohexanoic acid, mercaptooctanoic acid, mercaptodecanoic acid and mercaptododecanoic acid. .

The molar ratio of the mercapto acid solvent of the second liquid: the alkanolamine solvent may be 15:1 to 20:1, preferably 16:1 to 20:1, more preferably 17:1 to 20:1, and most preferably 18:1 to 20:1. At this time, it is preferable to prepare the second solution at a concentration of 0.2 to 1.0M, more preferably a concentration of 0.3 to 0.9M, more preferably a concentration of 0.4 to 0.8M, and most preferably 0.5 to 0.7M concentration, but is not limited thereto.

In one embodiment, the light absorption layer may be formed by coating a mixture of the first liquid and the second liquid in step (c) on the transparent electrode layer and annealing in an inert gas atmosphere.

The coating may be performed by a method commonly used in forming a film by applying a solution in the semiconductor field. For example, spin coating, roll coating, spray coating, blade coating, bar coating, dip coating, etc. may be performed, but the present invention is not limited by a specific coating method.

The annealing is to improve the crystallinity of the light absorption film generated by application of the solution, and the temperature during the first annealing or the second annealing may be 150 to 400° C., specifically 200 to 350° C., but is not limited thereto. During annealing, the inert gas atmosphere may be nitrogen, argon, helium, or a mixed gas atmosphere thereof.

In addition, before annealing, drying to remove the solvent from the applied liquid may be performed. Specifically, the drying may be carried out at a temperature of 180 to 300 ℃, it may be carried out for 1 to 10 minutes. More specifically, the drying may be a multi-stage drying including primary drying carried out at a temperature of 150 to 200 ℃ and secondary drying carried out at a temperature of 280 to 320 ℃. In multi-stage drying, primary drying and secondary drying may be performed independently of each other for 1 to 5 minutes, but the present invention is not limited by the drying time.

In one embodiment, in step (d), the charge transport layer may be formed by atomic layer deposition (ALD). Atomic layer deposition is a technique capable of depositing a thin film at the level of an atomic layer, and is a method of chemically adsorbing an introduced source gas to the substrate surface, purging the remaining source gas, and then forming a material layer from the adsorbed source gas. According to this method, since the thickness of the material layer can be adjusted in units of atomic layers, a material layer having excellent step coverage can be formed, and the concentration of impurities contained in the material layer is also very low.

In one embodiment, TiO ₂ may be used as the metal oxide, and as a precursor as a Ti source of the atomic layer deposition method, tetraisopropoxytitanium, tetrapropoxytitanium, tetrakis (dimethylamido) ) may be selected from the group consisting of titanium (tetrakis(dimethylamido)titanium; TDMAT), preferably TDMAT. In addition, the TiO ₂ charge transport layer may be deposited on the light absorption layer through an atomic layer deposition method using H ₂ O as an O source.

In one embodiment, the step of forming the catalyst material layer in step (e) may be formed through sputtering of the catalyst. In addition, after step (e), the step of modifying the surface of the gas generating electrode with 3-(trimethoxysilyl)propyl methacrylate or alkoxysilaneamine may be further included.

In the method of manufacturing the electrode, the hydrogel protective layer in step (f) may be prepared by polymerizing a polymerizable monomer and a polyfunctional monomer containing an amine group. The polymerizable monomer for preparing the hydrogel protective layer may be applied without limitation as long as it is a polymerizable monomer including an amine group, and specifically, may be acrylamide or methacrylamide, but is not limited thereto. The amine group of the polymerizable monomer including the aldehyde group activated in step (e) and the amine group constituting the hydrogel protective layer is covalently bonded to each other so that it can be chemically bonded as well as a physical bond.

Hereinafter, the present invention will be described in detail through examples. However, these are for describing the present invention in more detail, and the scope of the present invention is not limited by the following examples.

<Example> Preparation of electrochemical electrode

1. Fabrication of the gas generating electrode

The Sb ₂ Se ₃ electrode was fabricated through spin coating on 70 nm thick Au-coated FTO glass. Since Sb ₂ Se ₃ is a low-cost material capable of collecting solar photons with a wavelength of up to 1050 nm, it was selected as a light absorption layer.

First, 0.258 g of SbCl ₃ was dissolved in 12 mL of 2-methoxyethanol (2-methoxy ethanol). In addition, 0.385 g of Se powder was dissolved in 8 mL of a solution in which the molar ratio of thioglycolic acid (TGA) and ethanol amine (EA) was TGA:EA = 95:5. After mixing the above two solutions to obtain a 20 mL Sb-Se solution, the Sb-Se solution was magnetically stirred at 80° C. overnight.

Spin coating was performed for 10 cycles. Each cycle consisted of spin-coating the Sb-Se solution at 2000 rpm for 30 seconds, followed by sequential drying in two steps at 180°C and 300°C for 3 minutes, respectively. The sample was then heat treated at 350° C. for 20 minutes. In order to prevent unnecessary oxidation reaction, spin coating and heat treatment were performed under N ₂ conditions. Finally, heat treatment was carried out at 200° C. for 30 minutes in air to burn off residual organic matter.

The TiO ₂ layer was deposited on the Sb ₂ Se ₃ layer using tetrakis(dimethylamido)titanium (TDMAT) and water as sources of Ti and O, respectively. The deposition process was performed for 600 cycles, each cycle consisting of 0.3 sec of TDMAT pulse, 15 sec of N ₂ purging, 0.2 sec of H ₂ O pulse and 15 sec of N ₂ purging. The approximate growth rate of TiO ₂ was 0.58 Åle.

The Pt promoter was sputtered on the TiO ₂ /Sb ₂ Se ₃ electrode under an applied current of 10 mA for 120 seconds.

2. Surface treatment of gas generating electrode

The surface of the Pt/TiO ₂ /Sb ₂ Se ₃ electrode was coated with sodium hydroxide (NaOH), (3-aminopropyl)triethoxysilane ( (3-aminopropyl)triethoxysilane; APTES) and glutaraldehyde were treated.

A 1N NaOH solution and a 50 vol% glutaraldehyde solution were diluted with deionized water (DI) to prepare a 0.1N NaOH and 0.5 vol% glutaraldehyde solution, and the APTES solution was diluted with an ethanol solution to prepare a 0.5 vol% APTES solution. did. The prepared Pt/TiO ₂ /Sb ₂ Se ₃ electrode was immersed in 0.1N NaOH solution for 5 minutes. After removing the NaOH solution, 0.5 vol% APTES solution was poured over the electrode for 5 minutes. After the APTES solution was removed, the electrode was washed 6 times with an ethanol solution. After the washing step, 0.5 vol% glutaraldehyde solution was poured onto the electrode for 30 minutes. The glutaraldehyde solution was removed from the electrode, and the electrode was washed with deionized water 6 times, and then dried at 60° C. for 30 minutes.

3. Deposition of PAAM hydrogel protective layer on gas generating electrode

The PDMS mold was prepared by cutting a thin film of silicone rubber. After washing the PDMS mold with ethanol and removing dust using double-sided tape, it was placed on the surface-treated electrode. A 100% w/v acrylamide (AAM) solution was prepared by dissolving 1 g of acrylamide powder in 1 mL of DI. 2% w/v N,N'-methylenebisacrylamide (N,N'-Methylenebisacrylamide; bis-acrylamide) was prepared by dissolving 20 mg of bis-acrylamide powder in 1 mL DI. A 10% w/v ammonium persulfate (AP) solution was prepared by dissolving 10 mg of AP powder in 100 μL DI. According to Table 1, an acrylamide solution, a bis-acrylamide solution, and deionized water were mixed to prepare a gel solution, and then degassed for at least 1 hour.

Volume (μL) Monomer concentration(%) 6% 10% 30% DI water 888 817.4 464 100% AAm 65.2 108.6 326 2% Bis-acrylamide 40.8 68 204 10% AP 5 5 5 TEMED One One One Total 1000 1000 1000

The concentration ratio of the monomer and the crosslinking agent was fixed at 80:1. The AP solution and N,N,N',N'-tetramethylethylenediamine (N,N,N',N'-tetramethylethylenediamine; TEMED) solution were added together with the pre-gel solution to start gelation. The final concentrations of AP and TEMED were 0.05wt% and 0.1wt%, respectively. After 30 minutes of gelation, the cover glass and the PDMS mold were carefully removed.

<Comparative example>

Except that steps 2 and 3 were not performed, it was prepared in the same manner as in the preparation method of Examples.

<Experimental Example 1> Analysis of electrical properties of electrochemical electrodes

1 is a graph showing the electrical characteristics of an electrochemical electrode when the concentration of the monomer constituting the hydrogel protective layer is different from each other. When the electrode was coated with the hydrogel, there was no significant change in the initial photocurrent density (J _ph ) and the onset potential at 0 V _RHE .

However, it was found that the lifetime of the electrode was significantly extended when the hydrogel protective layer was used.

Figure 2 is a graph showing the stability of the electrode in an acidic (pH 1) electrolyte when the concentration of the monomer constituting the hydrogel protective layer is different. In the case of using a 10% hydrogel protective layer, while maintaining about 70% of the initial photocurrent density and showing stability for more than 90 hours, the electrochemical electrode according to the comparative example showed a rapid photocurrent decrease, and was almost completely damaged within 3 hours became Through this, the electrode using the hydrogel protective layer did not have a significant difference compared to the case where the protective layer was not used in terms of initial photocurrent density or onset potential, but it was confirmed that it was improved by more than 100 times in terms of stability.

In addition, as can be seen in FIGS. 3 and 4 , as a result of testing the stability of the electrode using a neutral (pH 7) electrolyte or a basic (pH 8) electrolyte, an electrode using a hydrogel protective layer as in the case of using an acidic electrolyte It was confirmed that the electrode and hydrogel protective layer of the present invention can be used in various electrolytes by confirming that the initial photocurrent density is maintained for a long time.

<Experimental Example 2> Structural analysis of electrodes

By observing the surface structure of the Sb ₂ Se ₃ electrode, it was confirmed that the hydrogel protective layer provided structural stability to the PEC device.

5 to 7 , in the case of the electrochemical electrode according to the comparative example, a phenomenon in which part of Pt was separated or agglomerated was observed after driving for 5 hours, and it was confirmed that the TiO ₂ layer was completely dissolved. In contrast, when the 10% hydrogel protective layer was coated, not only Pt remained well attached even after 100 hours of operation, but also it was confirmed that the TiO ₂ layer was hardly damaged. That is, the hydrogel protective layer not only prevents the desorption of platinum particles present on the electrode surface, but also has a high concentration of metal ions dissolved from the periphery of the hydrogel protective layer-coated electrode surface. It was confirmed that there is an effect of inhibiting the dissolution of additional metal ions.

<Experimental Example 3> Generation and separation of air bubbles in the electrode

8 is a diagram illustrating the formation, growth and separation of air bubbles on the surface without a hydrogel protective layer and on the electrode surface with a 10% hydrogel protective layer through a high-speed camera.

On the surface of the electrochemical electrode according to the comparative example, bubbles grew in a spherical shape within 200 ms. In contrast, in the case of the electrode surface with a 10% hydrogel protective layer, the bubble was oval and grew to a size similar to the thickness of the hydrogel, reaching the 'confinement-free region' (CFR) within 8 seconds, and the grown bubble was As the gel was separated from the protective layer, it was confirmed that an elliptical 'bubble path' was formed in the direction perpendicular to the electrode surface. The movement of bubbles to areas other than the bubble path was hardly observed, which means that the hydrogen gas molecules generated on the electrode surface gather and escape through the bubble path. That is, it was confirmed that, when a 10% hydrogel protective layer was used, it was possible to induce rapid desorption of hydrogen bubbles generated on the electrode surface.

In addition, in order to understand the role of the hydrogel protective layer on the stability of the electrode, the effect of bubble separation was analyzed by adding a surfactant to the electrolyte.

9 is a graph evaluating the stability of the Pt/TiO ₂ /Sb ₂ Se ₃ electrode when the concentration of the surfactant is changed. Changes in the photocurrent can be observed due to the formation and separation of large bubbles that coalesce from microbubbles. Large bubbles can temporarily lower the photocurrent density by scattering incoming light or blocking the electrochemically active area. Although surfactant was added to the electrolyte to prevent the formation of large bubbles and reduce the change in photocurrent, the stability was hardly improved.

In conclusion, in the case of using a 10% hydrogel protective layer, not only can it induce rapid desorption of hydrogen bubbles generated on the surface, but also in a situation where it is difficult to obtain high stability by simply separating the bubbles, not only the bubble separation but also the hydrogel It was confirmed that the safety was improved due to the structural and physical effects imposed by the network.

<Experimental Example 4> Stability evaluation according to the concentration of the hydrogel protective layer

The stability of the electrode depends on the concentration of the monomer for preparing the hydrogel protective layer. In order to explain how the mechanical properties of the hydrogel contribute to the bubble path formation, when using 6%, 10%, and 30% hydrogel protective layers, each hydrogen bubble generation was observed.

Figure 10 shows an image of the bubble just before separation after reaching the CFR (hydrogel/electrolyte interface). In the case of the 6% hydrogel protective layer, adjacent bubble paths merge with each other to form a large bubble inside the hydrogel network, and it was confirmed that the abnormally large bubble covered the entire surface. In the case of the 30% hydrogel protective layer, hydrogen bubbles were either trapped near the electrode/hydrogel protective layer interface by the high-density hydrogel network or ejected in the form of small bubbles. Bubbles trapped near the electrodes were expanded by the additionally generated hydrogen gas and coalesced to form large bubbles. Since these large bubbles scatter most of the incident light, it was confirmed that the photocurrent rapidly dropped in the stability test. In contrast, in the 10% hydrogel protective layer, bubbles escape along the bubble path, and unlike the 6% or 30% hydrogel protective layer, abnormally large bubbles are not generated, so that the photocurrent is relatively constant in the stability test. was confirmed to be maintained.

In addition, when using a low rigidity hydrogel protective layer using a low concentration hydrogel protective layer, as can be seen in FIGS. It was confirmed that the current was close to 0 due to the problem of covering the .

In conclusion, when the hydrogel protective layer having a specific range of rigidity is coated by controlling the concentration of the hydrogel protective layer, an electrode having excellent stability can be prepared.

<Experimental Example 5> Stability evaluation according to the thickness of the hydrogel protective layer

13 is a graph evaluating the stability of the Pt/TiO ₂ /Sb ₂ Se ₃ electrode when the thickness of the hydrogel protective layer is changed. If the thickness of the hydrogel protective layer is more than 2,000 μm, the initially growing bubbles hardly reach the CFR, resulting in the accumulation of large bubbles near the surface. Conversely, if the thickness of the hydrogel protective layer is reduced to 10 μm, a relatively large bubble path is formed because the bubbles reach the CFR quickly. Thus, a bubble large enough to cover the entire PEC element is formed. As large bubbles were formed, peeling of the protective layer, which was not found under other conditions, was observed. As a result, when using a 10% hydrogel protective layer with a thickness of 100 μm, it exhibited low stability similar to that without a protective layer.

More specifically, in a thin hydrogel protective layer, the pressure due to bubble expansion is concentrated on the interface between the hydrogel protective layer and the device. Therefore, when the maximum pressure (P _max ) due to bubble expansion is greater than the bonding strength between the hydrogel protective layer and the electrode interface, there is a problem in that the hydrogel protective layer is detached. In this case, there is a problem in that the electrode surface is damaged within a few hours, and the current also rapidly decreases. 14 and 15, when including a hydrogel protective layer having a thickness of 100 μm, it can be confirmed that the hydrogel protective layer is detached from when J _ph /J ₀ is about 80%, but the thickness of 200 μm In the case of including a hydrogel protective layer, it was confirmed that the hydrogel protective layer was desorbed from when J _ph /J ₀ was about 50%.

In addition, in the thick hydrogel protective layer, the bubbles generated in the device are accumulated in the hydrogel trapped state. There is a problem in that the current decreases as the size of the trapped bubble increases. Referring to FIG. 16 , when the thickness of the hydrogel protective layer is about 1,200 μm, it can be confirmed that air bubbles are accumulated on the surface from when J _ph /J ₀ is about 80%.

In conclusion, referring to FIGS. 17 and 18 , when the thickness of the hydrogel protective layer is within a certain range, the electrode having excellent stability by preventing the desorption of the hydrogel protective layer and at the same time preventing bubbles from accumulating on the surface can be manufactured.

In summary, the electrode proposed in the present invention has demonstrated its performance by implementing an electrode with improved stability through structural and physical protection while inducing rapid desorption of hydrogen bubbles generated from the surface, and has better performance than the existing invention. can confirm.

Claims (21)

transparent electrode layer;
A gas generating electrode comprising; a catalyst material layer positioned on the transparent electrode layer; and
Includes; hydrogel protective layer covering the gas generating electrode;
The hydrogel protective layer is conformally bound on the gas generating electrode, the electrochemical electrode.
According to claim 1,
An electrochemical electrode comprising a light absorption layer and a charge transport layer between the transparent electrode layer and the catalyst material layer.
3. The method of claim 2,
The light absorption layer comprises a material selected from the group consisting of post-transition metals, metalloids and transition metals, electrochemical electrode.
3. The method of claim 2,
The charge transport layer comprises a metal or metal oxide, electrochemical electrode.
According to claim 1,
The catalytic material layer is an electrochemical electrode comprising at least one catalyst selected from the group consisting of metals and their oxides, nitrides, oxynitrides, carbides, sulfides, phosphides, and alloys.
According to claim 1,
The thickness of the hydrogel protective layer is 10 to 2,000 μm, the electrochemical electrode.
According to claim 1,
The pore diameter of the hydrogel protective layer is 1 to 1,000 nm, the electrochemical electrode.
According to claim 1,
The surface of the gas generating electrode comprises a first region in which the catalytic material layer is located and a second region in which the catalytic material layer is not located.
According to claim 1,
The hydrogel protective layer is covalently bonded to the surface of the gas generating electrode, electrochemical electrode.
According to claim 1,
The hydrogel protective layer is an electrochemical electrode comprising a multimer having an electric charge.
According to claim 1,
The hydrogel protective layer has a rigidity and ductility such that when the _rs value is 0.2 mm or less, the P _max /P _f value is 1 or less, the electrochemical electrode.
(Where _rs is the radius of the initial crack of the hydrogel, P _max is the maximum pressure applied to the hydrogel as the bubble expands, and P _f is the critical pressure required for cracking of the hydrogel.)
12. The method of claim 11,
The bonding strength of the hydrogel protective layer and the gas generating electrode is stronger than P _max , the electrochemical electrode.
(a) preparing a first liquid containing an alkoxyalcohol-based solvent;
(b) preparing a second liquid comprising a mercapto acid-based solvent and an alkanolamine-based solvent;
(c) forming a light absorption layer by applying a mixture of the first liquid and the second liquid to the transparent electrode layer;
(d) forming a charge transfer layer on the light absorption layer formed in step (c);
(e) forming a catalyst material layer on the charge transport layer formed in step (d); and
(f) forming a hydrogel protective layer covering the gas generating electrode including the light absorption layer, the charge transfer layer and the catalyst material layer formed in the steps (c) to (e); .
14. The method of claim 13,
The mercapto acid-based solvent is selected from the group consisting of mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, mercaptohexanoic acid, mercaptooctanoic acid, mercaptodecanoic acid and mercaptododecanoic acid, A method for manufacturing an electrochemical electrode.
14. The method of claim 13,
The alkanolamine-based solvent is a compound represented by the formula of NH ₂ -(CH ₂ ) _m -OH (m is an integer of 1 to 4), a method of manufacturing an electrochemical electrode.
14. The method of claim 13,
The molar ratio of the mercapto acid-based solvent and the alkanolamine-based solvent of the second liquid is 18:1 to 20:1, the method of manufacturing an electrochemical electrode.
14. The method of claim 13,
In the step (c), the mixed solution is coated on the transparent electrode layer and annealed in an inert gas atmosphere, the method of manufacturing an electrochemical electrode.
14. The method of claim 13,
In the step (d), the charge transport layer is formed by atomic layer deposition (ALD), the method of manufacturing an electrochemical electrode.
14. The method of claim 13,
After the step (e), 3- (trimethoxysilyl) propyl methacrylate or alkoxysilane amine further comprising the step of modifying the surface of the gas generating electrode, the electrochemical electrode manufacturing method.
14. The method of claim 13,
In the step (f), the hydrogel protective layer is prepared by polymerizing a polymerizable monomer and a polyfunctional monomer containing an amine group, the method for producing an electrochemical electrode.
A method for producing a gas selected from the group consisting of hydrogen, oxygen, nitrogen and chlorine using the electrochemical electrode according to claim 1 .

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