KR102210525B1 - Electrode for Oxygen Evolution Reaction and The Fabrication Method Thereof - Google Patents

Abstract

The present invention relates to an oxygen evolution reaction (OER) electrode, wherein the OER electrode according to the present invention comprises: a first active metal substrate; And nanometer order doedoe fine particles having a diameter of (nanometer order) to 10 ¹ nanometer order (10 ¹ nanometer order) are randomly agglomerated, the surface layer having a porous by irregular aggregation; comprises, the fine particles of the second active It is a metal-containing hydroxide.

Description

Electrode for Oxygen Evolution Reaction and The Fabrication Method Thereof}

The present invention relates to an oxygen generating reaction electrode and a method of manufacturing the same, and more particularly, to an oxygen generating reaction electrode used for electrochemical water decomposition and a method of manufacturing the same.

As various environmental problems such as global warming and air and marine pollution occur, interest in clean and clean energy is increasing. Among them, hydrogen is the most efficient and clean renewable energy, and water produced by reacting with oxygen is the only reaction product. Hydrogen can be used in internal combustion engines or electrochemical cells to provide power or generate electricity. Fuel cells that use hydrogen as fuel are considered to be the most powerful alternative to fossil fuel-based engines as they are highly energy efficient and free from pollution emissions.

Hydrogen can be produced through petroleum cracking, biomass cracking, or water cracking. Water splitting is considered the cleanest and most efficient method of producing hydrogen, as it produces only two types of hydrogen and oxygen from water without producing other pollutants.

Water decomposition consists of two reactions, one is a cathodic (reduction) reaction, which is a hydrogen evolution reaction (HER), and the other is an anodic (oxidation) reaction, which is an oxygen evolution reaction (OER). to be. The water decomposition reaction between HER and OER can be accomplished through a photocatalytic, electrocatalyst or photoelectric catalyst system. Among the total reactions between HER and OER, OER is a reaction that determines the overall rate and efficiency of water decomposition reactions due to high overvoltage and low stability of the catalyst. Accordingly, research for developing an OER catalyst having a low overvoltage and high durability has been continuously conducted. The state of the art of OER catalysts is a technology that uses iridium dioxide (IrO ₂ ) or ruthenium dioxide (RuO ₂ ) nanoparticles as catalysts, but iridium and ruthenium are expensive and rare metals and are not commercially viable.

Accordingly, there is a need to develop an OER catalyst (electrode) based on non-rare metals such as Ni, Fe, Co, Mo, etc., but having superior OER activity and durability than iridium dioxide or ruthenium dioxide.

J. Lim, D. Park, S. S. Jeon, C. W. Roh, J. Choi, D. Yoon, M. Park, H. Jung, H. Lee, Advanced Functional Materials 2018, DOI 10.1002/adfm. 201704796.

The present invention is to provide an oxygen generating reaction electrode that can be commercialized based on a non-rare metal, has high OER activity at low overvoltage, and has excellent durability.

An oxygen evolution reaction (OER) electrode according to the present invention comprises: a first active metal substrate; And doedoe nanometer order fine particles having a diameter of (nanometer order) to 10 ¹ nanometer order (10 ¹ nanometer order) are randomly agglomerated, the surface layer having a porous by irregular aggregation; includes, fine particles of the second active metal It is a hydroxide containing.

In the OER electrode according to an embodiment of the present invention, by oxidation of the first active metal and reduction of the second active metal caused by the standard reduction potential difference between the first and second active metals, the surface layer is It may be formed directly (in-situ) on the surface of the active metal substrate.

In the OER electrode according to an embodiment of the present invention, in the elemental composition (atomic%) between the first active metal, the second active metal, and oxygen, measured by X-ray photoelectron spectroscopy (XPS) The composition may be 3.5 to 10.0 atomic%, and the composition of the first active metal may be 16.0 to 30.0 atomic%.

In the OER electrode according to an embodiment of the present invention, the surface layer contains both a trivalent second active metal and a tetravalent second active metal, and is calculated from X-ray photoelectron spectroscopy 2P _3/2 spectrum of the second active metal. The atomic ratio of the tetravalent second active metal/3valent second active metal may be 0.2 or more.

In the OER electrode according to an embodiment of the present invention, M-OH calculated from the X-ray photoelectron spectroscopy analysis O 1s spectrum of oxygen using M as a metal selected from at least one of the first and second active metals The ratio of /MO may be 5 or more.

In the OER electrode according to an embodiment of the present invention, the first active metal substrate is a foam, film, mesh, felt, or perforated film of the first active metal. Can be

In the OER electrode according to an embodiment of the present invention, the fine particles may be amorphous.

In the OER electrode according to an embodiment of the present invention, in addition to the diffraction peak derived from the first active metal, on the X-ray diffraction pattern using Cu Kα, the diffraction peak may be located in a region of 2θ 21 to 24°.

In the OER electrode according to an embodiment of the present invention, the first active metal may be Ni, and the second active metal may be Fe, Mo, or Fe and Mo.

The OER electrode according to an embodiment of the present invention may have an overvoltage of 250 mV or less based on a current density of 10 mA/cm ² .

The OER electrode according to an exemplary embodiment of the present invention may have a Tapel slope of 84 mV/decade or less.

In the OER electrode according to an embodiment of the present invention, the double layer capacitance value of the oxygen generating reaction electrode calculated by the cyclic voltammetry may be 1.2 μFcm ^{-2 or} more.

The present invention includes an electrochemical water decomposition cell comprising the above-described OER electrode.

The present invention includes an apparatus comprising an electrochemical water cracking cell comprising the aforementioned OER electrode.

The device according to an embodiment of the present invention may further include a solar cell connected in series with the electrochemical water decomposition cell.

The present invention includes a method of manufacturing an OER electrode.

The method of manufacturing an OER electrode according to the present invention includes: contacting a first active metal with a precursor of a second active metal having a higher standard reduction potential than the first active metal, an inorganic acid, and a reaction solution containing hydrogen peroxide; do.

In the method of manufacturing an OER electrode according to an embodiment of the present invention, the volume fraction occupied by the inorganic acid and hydrogen peroxide in the reaction solution may be 0.05% to 3.00%.

In the method of manufacturing an OER electrode according to an embodiment of the present invention, the volume ratio of the inorganic acid: hydrogen peroxide in the reaction solution may be 0.5 to 10:1.

In the method of manufacturing an OER electrode according to an embodiment of the present invention, the inorganic acid may include sulfuric acid.

The OER electrode according to the present invention is a transition metal-based OER electrode, which is a non-rare metal, and has excellent OER activity with very low overvoltage and small tapel slope, and excellent durability because low overvoltage is stably maintained even during long-term reactions up to 500 hours. There are advantages to having.

The method of manufacturing an OER electrode according to the present invention can produce an electrode having excellent OER activity and durability by a simple process of contacting a reaction solution containing a first active metal and a second active metal only at room temperature and pressure. It is an efficient method and has the advantage of excellent commerciality.

1 is a NF-Fe-W (Fig. 1 (d) to (f)), NF-Fe-PS (Fig. 1 (g) to (i)) of NF (Fig. 1 (a) to (c)) This is a scanning electron microscope photograph of the surface.
FIG. 2 is a transmission electron microscope observation photograph of a cross section of NF-Fe-PS (FIGS. 2(a) to (c) and elemental mapping results of particles deposited on the nickel foam surface (FIG. 2(d) to (g))). It is a drawing.
3 is a diagram showing the XPS measurement results of each of NF-Fe-PS, NF-Fe-W, and NF, FIG. 3(a) is a full spectrum, FIG. 3(b) is a Ni 2p spectrum, and FIG. 3(c) ) Is a Fe 2p spectrum, Figure 3 (d) is a diagram showing the O 1s spectrum.
4 is a diagram showing the XPS measurement results of each of NF-Fe-H2O2 and NF-Fe-H2SO4, FIG. 4(a) is a full spectrum, FIG. 4(b) is a Ni 2p spectrum, and FIG. 4(c) is Fe 2p spectrum, Figure 4 (d) is a diagram showing the O 1s spectrum.
5 is a diagram showing the results of X-ray diffraction measurements of NF, NF-Fe-PS, NF-Fe-H2O2, and NF-Fe-H2SO4.
6 is a view showing the measurement of the electrochemical activity of each OER electrode using NF, RuO2, NF-Fe-W, NF-Fe-PS, NF-Fe-H2SO4, and NF-Fe-H2O2 as OER electrodes.
7 is a diagram showing the results of LSV (Linear Sweep Voltammetry) measurement for each OER electrode of NF-PS, NF-W, NF-H2SO4, and NF-H2O2 to which Fe is not introduced.
8 is a diagram showing the electrochemical impedance spectra (EIS) of each OER electrode of NF, NF-Fe-W, NF-Fe-PS, NF-Fe-H2SO4, NF-Fe-H2O2, The drawing inserted in the upper left is a diagram showing an equivalent circuit.
9 is a diagram showing the CV measurement results (scan speed = 20 mV/s) of each OER electrode of NF, NF-Fe-W, NF-Fe-PS, NF-Fe-H2SO4, and NF-Fe-H2O2.
10 is a diagram showing a result of a durability test of NF-Fe-PS manufactured in Example.
11 is a diagram showing the XPS measurement results of each of NF-Fe-PS (Fresh in FIG. 11) before durability test and NF-Fe-PS (After in FIG. 11) after 500 hours durability test, FIG. 11(a) ) Is a full spectrum, FIG. 11(b) is a Ni 2p spectrum, FIG. 11(c) is a Fe 2p spectrum, and FIG. 11(d) is a view showing an O 1s spectrum.
12 is a diagram showing a result of testing the catalyst stability of NF-Fe-PS prepared in Example.
13 is a diagram showing the CV results of each OER electrode of NF, NF-Fe-W, NF-Fe-PS, changing the scan speed to 10, 20, 50, 100, or 200 mV/s for each OER electrode It is a diagram (Fig. 13(d)) showing the measured result and the difference in anode and cathode current density (Ja-Jc) according to the scan speed at 0.65V.
14 is a diagram showing an optical photograph and time-current (chronoamperometric) characteristics of a solar cell-water electrolysis system constructed so that water electrolysis is performed by power generated from a solar cell.

Hereinafter, an oxygen generating reaction electrode of the present invention and a method of manufacturing the same 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, unless there are other definitions in the technical terms and scientific terms used, they have the meanings commonly understood by those of ordinary skill in the technical field to which this invention belongs, and the gist of the present invention in the following description and accompanying drawings Descriptions of known functions and configurations that may be unnecessarily obscure will be omitted.

The oxygen evolution reaction (hereinafter referred to as OER) electrode may be an OER electrode for electrochemical water decomposition, and may be an OER electrode for electrochemical water decomposition based on an alkaline electrolyte, but is not limited thereto.

The active metal may be a transition metal known as a catalyst material for accelerating the oxygen evolution reaction. The first active metal and the second active metal are different transition metals (catalysts), but in one embodiment, the second active metal may be an active metal whose standard reduction potential is higher than the standard reduction potential of the first active metal. In one embodiment, the first active metal and the second active metal may be two or more transition metals selected from Mn, Fe, Co, Ni, Mo and Cu, Ru, Ir, etc., and the lowest standard reduction among the selected transition metals. The transition metal having a potential may be the first active metal, but is not limited thereto.

The OER electrode according to the present invention includes a first active metal substrate; And doedoe nanometer order fine particles having a diameter of (nanometer order) to 10 ¹ nanometer order (10 ¹ nanometer order) are randomly agglomerated, the surface layer having a porous by irregular (random) aggregation; includes, microparticles of claim 2 It may be a hydroxide containing an active metal.

Nanometer order is 10 ⁰ may mean the nanometer order (10 ⁰ nanometer order), which may indicate the size of the nanometer order to 10 ^nanometer order is several nanometers to several tens of nanometers to 1 in detail It may be 90 nm, more specifically 5 to 50 nm, substantially 10 to 40 nm, and more substantially 10 to 30 nm.

Irregular aggregation may include irregular aggregation between particulates, between secondary particles (agglomerated particles of particulates) and/or between particulates and secondary particles. The surface layer is irregular and may have a porous structure having open pores having a very wide size distribution ranging from a few nanometers to hundreds of nanometers, specifically, from 2 nm to 500 nm due to sparse aggregation. As the surface layer has an open porous structure, not only the second active metal-containing hydroxide fine particles of the surface layer, but also the surface of the first active metal substrate to which the fine particles are not directly bound may affect OER activity. In this case, the thickness of the surface layer is not particularly limited, but may be in the range of 5 to 500 nm.

The surface layer may include fine particles of a hydroxide containing the second active metal, and the second active metal of the hydroxide containing the second active metal may have both trivalent and tetravalent oxidation values. That is, the surface layer may contain both a trivalent second active metal and a tetravalent second active metal.

The tetravalent second active metal is advantageous because it provides an OER reaction active point and can greatly improve OER activity. OER electrode, specifically, the atomic ratio of the tetravalent second active metal/3valent second active metal contained in the surface layer is 0.2 or more, specifically 0.4 or more, more specifically 0.5 or more, and even more specifically 0.7 or more May be, and may be substantially 3.0 or less. This atomic ratio may be calculated from the 2P _3/2 spectrum of X-ray photoelectron spectroscopy of the second active metal. Specifically, by using the previously known binding energy for each bond and state according to the specific material of the second active metal, the ratio of the peak area due to the tetravalent second active metal and the peak area due to the trivalent second active metal The atomic ratio can be calculated.

Characteristically, the surface layer may include second active metal hydroxide fine particles, and the second active metal hydroxide may be represented by the formula M2(OH)y. In this case, M2 means a second active metal. In M2(OH)y, y may be a real number that satisfies the charge neutrality according to the molar ratio of the trivalent second active metal and the tetravalent second active metal by making the total number of moles of the second active metal contained in the surface layer 1 .

However, it should not be interpreted as being limited to that the surface layer consists only of the second active metal hydroxide fine particles. The surface layer is formed with fine particles, which are the hydroxides of the second active metal, the hydroxide of the first active metal in the form of particles, the complex hydroxide of the first active metal and the second active metal in the form of particles, the oxide of the first active metal in the form of particles, and the second in the form of particles. An oxide of an active metal, a composite oxide of a particulate first active metal and a second active metal, or a mixture thereof, or both may be further included. Specifically, the oxide contained in the surface layer is an oxide selected from one or two or more oxides containing a second active metal, an oxide containing a first active metal, and an oxide containing both the first and second active metals. I can. In this case, the case where the surface layer includes both an oxide and a hydroxide may include a case where an oxide and a hydroxide are mixed in a single fine particle, or a case where an oxide particle and a hydroxide fine particle are mixed in the surface layer, or both.

In one embodiment, the hydroxide fine particles containing the second active metal, specifically, the second active metal hydroxide fine particles may be amorphous (amorphous). At this time, in addition to the diffraction peak derived from the first active metal (diffraction peak of the first active metal) on the X-ray diffraction pattern using Cu Kα of the OER electrode due to the irregularity of the amorphous phase, the diffraction peak is located in the region of 2θ 21 to 24°. can do. At this time, the diffraction peak located in the 2θ 21 to 24° region may be due to the hydroxide or oxide fine particles containing the second active metal, and the FHWM (Full width at half maximum) of the diffraction peak is 5° or more, specifically 5 It can be a very broad peak of to 10 degrees.

As described above, since the surface layer has an open porous structure and the base material is also an active metal, the surface of the base material, particularly the base material, may also affect OER activity during the oxygen evolution reaction.

The surface of the substrate to which the fine particles are not bound may be a surface in which the -OH functional group is formed, and the surface first active metal positioned on the surface of the substrate may be bonded with the -OH functional group. Thus, at least the surface area of the substrate to which the fine particles are not bound may be the surface on which M1s(OH)z is formed, in which case M1s refers to the first active metal atom (surface atom) located on the surface of the substrate, and z is the first active metal atom (surface atom). 1 It may be a mistake that satisfies neutrality depending on the oxidation value of the active metal.

The fine particles, which are the second active metal hydroxide, and the first active metal bonded with the -OH functional group on the surface of the substrate can have superior OER activity and durability than the composite hydroxide of each of the first and second active metals due to the synergistic effect between them. have. Although not necessarily limited to this interpretation, a large amount of tetravalent second active metal may be contained by the fine particles as the second active metal hydroxide and the first active metal bonded with the -OH functional group on the surface of the substrate, and long-term oxygen generation Even during the reaction, the tetravalent state of the second active metal can be stably maintained.

In one embodiment, the OER electrode has a metal selected from one or more of the first and second active metals as M, and the ratio of M-OH/MO calculated from the X-ray photoelectron spectroscopy analysis O 1s spectrum of oxygen is May be 5 or more. When both the first active metal and the second active metal are combined with -OH, the catalytic activity may be remarkably enhanced and a synergy effect between the fine particles and the surface of the substrate may be exhibited. On the other hand, through various comparative experiments and additional experiments, it is judged that the binding of M-O, that is, metal oxide, does not substantially cause a synergy effect between the fine particles and the substrate surface, or enhance the catalytic activity.

Specifically, the OER electrode has an atomic ratio of the first active metal in the oxidized state / the first active metal in the metal state is 10 based on the 2P 3/2 spectrum of X-ray photoelectron spectroscopy analysis of the first active metal. It may be below.

In one embodiment, the OER electrode is measured by X-ray photoelectron spectroscopy (XPS), the second active metal is 3.5 to 10 atomic% in the elemental composition (atomic %) between the first active metal, the second active metal and oxygen , Specifically 4.0 to 8.0 atomic%, more specifically 4.0 to 6.0 atomic%, the first active metal may be 16.0 to 30.0 atomic%, specifically 20 to 25 atomic%, more specifically 20 to 24 atomic% However, it is not necessarily limited thereto. In this case, the elemental composition (atomic %) between the first active metal, the second active metal, and oxygen means an elemental composition in which the total amount of the first active metal, the second active metal, and oxygen is 100.

In one embodiment, the first active metal substrate may be a foam, foil, mesh, felt, or perforated film of the first active metal, in terms of improving the surface area. Foam, mesh, felt, etc. are advantageous, but are not necessarily limited thereto.

In one embodiment, the surface layer is formed on the surface of the first active metal substrate by oxidation of the first active metal and reduction of the second active metal generated by a standard reduction potential difference between the first and second active metals of the substrate. It may be formed directly (in-situ). In addition, the bonding between the -OH functional group and the first active metal located on the surface of the substrate may also be made simultaneously in the process of directly forming the surface layer. Thus, in one embodiment, the second active metal may be an active metal whose standard reduction potential is higher than the standard reduction potential of the first active metal, and oxidation of the first active metal and reduction of the second active metal are corrosion reactions. Can be That is, the surface layer may be a porous deposited layer in which the first active metal of the substrate contacts ions of the second active metal having a higher standard reduction potential than the first active metal, and is deposited by spontaneous corrosion reaction.

As the fine particles of the surface layer are produced in-situ on the surface of the first active metal substrate by the above-described corrosion reaction, the fine particles of the hydroxide containing the second active metal in contact with the surface of the first active metal substrate 1 It forms an interface boundary with the active metal substrate, and may be in a state bound to the first active metal substrate.

In an advantageous example, the first active metal may be Ni, and the second active metal may be Fe, Mo, or Fe and Mo. When the first active metal of the OER electrode is Ni and the second active metal is Fe, Mo, or Fe and Mo, hydroxide particles containing iron, molybdenum or iron and molybdenum are combined with -OH functional groups on the surface of the substrate. The synergistic effect between the surface Ni ²⁺ shows excellent OER activity at surprisingly low overpotential, and at the same time, the OER activity can be stably maintained for a long time in an alkaline electrolyte.

Low overvoltage means that less power is used for the same level of water decomposition, and the amount of water decomposition can be increased with the same power. Thus, low overvoltage is one of the important factors that determine the commercialization of electrochemical water decomposition. In one embodiment, the OER electrode may have an overvoltage of 250mV or less, specifically, 245mV or less, based on a current density of 10mA/cm ² , and may have an overvoltage of substantially 150mV or more.

The Tafel slope is a standard for OER electrode activity and is an index indicating the degree of increase in electrical potential due to an increase in oxygen generation. The lower the tapel slope, the smaller the voltage required for decomposition of water, and the tapel slope along with the overvoltage is one of the important factors that determine commercialization. In one embodiment, the OER electrode may have a Tafel slope of 84 mV/decade or less, specifically 83 mV/decade, and may have a Tafel slope of substantially 30 mV/decade or more.

In addition, the double layer capacitance (C _dl ) value of the OER electrode calculated using cyclic voltammetry (CV) is an index indicating the amount of reactive active points of the OER electrode. In one embodiment, the double layer capacitance value of the OER electrode calculated by cyclic voltammetry may be 1.2 μFcm ^-2 or more, specifically 1.3 μFcm ^-2 or more, and substantially 2.5 μFcm ^-2 or less.

In addition, the OER electrode may have excellent durability in which the overvoltage is maintained at 270mV or less even under an alkaline electrolyte, a current density of 10mA/cm ² and a reaction condition of 500 hours.

In addition, the OER electrode has a very low charge transfer resistance (Rct) calculated using an electrochemical impedance spectrum of 0.8 Ω or less, specifically 0.6 Ω or less, and thus may have more improved OER activity.

At this time, the electrochemical properties (activity) of the OER electrode may be physical properties (activity) based on an OER electrode, a Pt counter electrode, and an alkaline electrolyte solution of 1M KOH according to an embodiment. In addition, the voltage presented is a reversible hydrogen electrode reference potential value (vs.RHE), unless otherwise limited, regarding the electrochemical properties (activity) of the OER electrode.

The present invention includes an apparatus comprising an electrochemical water cracking cell comprising the aforementioned OER electrode. The hydrogen generation reaction (HER) electrode and electrolyte of the electrochemical water decomposition cell may be any HER electrode and alkaline electrolyte commonly used in the electrochemical water decomposition field. As a specific example, the alkali electrolyte may be a solution containing an alkali selected from the group consisting of KOH, NaOH and CsOH at a concentration of 0.1M to 2M, and the HER electrode is hydrogen such as Pd, Pt, Rh, Ir, Re, Ru, etc. Electrodes provided with a generation catalyst may be mentioned, but it goes without saying that the present invention cannot be limited by the type of specific HER electrode or the type of alkaline electrolyte.

In one embodiment, the device may further include a solar cell connected in series with the OER electrode and the HER electrode of the electrochemical water cracking cell. If the device further includes a solar cell, water is electrolyzed by electricity produced from solar energy and hydrogen can be produced, thereby increasing energy efficiency, and converting solar energy into chemical energy called hydrogen. It is the cleanest energy production device. It goes without saying that the solar cell provided in the device may be in the form of a solar cell module in which two or more solar cells are connected in series/parallel as well as a single solar cell so that an appropriate voltage can be applied to the cell in consideration of the desired hydrogen production rate. .

The present invention includes a method of manufacturing the OER electrode described above.

The method of manufacturing an OER electrode according to the present invention includes: contacting a first active metal with a precursor of a second active metal having a higher standard reduction potential than the first active metal, an inorganic acid, and a reaction solution containing hydrogen peroxide; do. At this time, the first active metal may be in the form of foam, foil, mesh, felt, or perforated film, and a desired corrosion reaction by contact with the reaction solution. The completed first active metal corresponds to the first active metal substrate described above in the OER electrode.

The reaction solution used for manufacturing the OER electrode may be an aqueous solution containing an inorganic acid and hydrogen peroxide. When the reaction solution contains an inorganic acid and hydrogen peroxide at the same time, by synergistic effect between an inorganic acid and hydrogen peroxide, in particular, sulfuric acid and hydrogen peroxide, an electrode having remarkably superior OER activity than a reaction solution containing inorganic acid alone or hydrogen peroxide alone can be prepared.

In one embodiment, the inorganic acid may be sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or a mixed acid thereof, and as a precursor of the second active metal, chloride, sulfate, nitrate, acetate, hydroxide, these And a mixture of these or a hydrate thereof, but are not necessarily limited thereto.

In an advantageous example, when the reaction solution contains an inorganic acid, particularly sulfuric acid and hydrogen peroxide at the same time, a spontaneous corrosion reaction, which is a reduction reaction of the oxidation of the first active metal and the second active metal ions derived from the precursor of the second active metal, is performed. Through this, the second active metal hydroxide fine particles can be deposited, and the content of the tetravalent second active metal in the fine particles can be greatly increased, which is advantageous.

In addition, when the reaction solution contains an inorganic acid, particularly sulfuric acid and hydrogen peroxide at the same time, the oxide (MO) form of M, which is the first or second active metal, is suppressed, and the formation of the hydroxide of M and the bonding of M and -OH functional groups It is promoted and is advantageous.

In one embodiment, the volume fraction occupied by the inorganic acid and hydrogen peroxide in the reaction solution may be 0.05% to 3.00%, specifically 0.05 to 1.00%, and more specifically 0.05 to 0.50%. By this volume fraction, the oxidation rate of the first active metal and the reduction rate of the second active metal (ions) are appropriately controlled, so that the surface layer having a porous structure of the above-described fine particles, especially, is very wide and large from several nanometers to hundreds of nanometers. It is advantageous because a surface layer having an open pore distribution can be stably formed.

In one embodiment, the volume ratio of inorganic acid: hydrogen peroxide in the reaction solution may be 0.5 to 10:1, specifically 2.5 to 4.5:1. The volume ratio of these inorganic acids, particularly sulfuric acid: hydrogen peroxide, causes a greater synergistic effect, promoting the introduction of a tetravalent second active metal and bonding with the -OH functional group of the surface first active metal, and at the same time, an oxide of the active metal (MO ) It is advantageous because it can suppress the formation.

In one embodiment, the contact between the reaction solution and the first active metal is performed using any contact method, as long as the corrosion reaction of spontaneous oxidation of the first active metal and spontaneous reduction of the second active metal (ion) can occur smoothly. It is also okay. As a practical example, a method such as applying a reaction solution to the first active metal or immersing the first active metal in the reaction solution may be used, but, of course, the present invention cannot be limited by the specific contact method.

As the OER electrode is manufactured using a corrosion reaction, the contact between the reaction solution and the first active metal is sufficient if it is performed at room temperature (20 to 25°C) and atmospheric pressure (1 atm), but is not limited thereto.

The contact time between the reaction solution and the first active metal, that is, the corrosion reaction time, may be such that the target surface layer is stably formed. For example, the contact may be made for 0.5h to 2h, but is not limited thereto .

In addition, after the corrosion reaction is completed, it goes without saying that the step of washing the first active metal substrate on which the surface layer is formed (the first active metal in which the reaction has been completed) may be further performed. At this time, the surface layer and the first active metal substrate are similar to or the same as those described above for the OER electrode, and thus, the method of manufacturing the OER electrode according to an embodiment of the present invention includes all the details described above for the OER electrode.

(Example 1)

Nickel foam (Wellcos corp. thickness = 0.8 mm, hereinafter NF) was cut to a size of 2x5 cm ² and then ultrasonically washed sequentially using 2M HCl, ethanol and water. The washed NF was stored overnight in a vacuum oven at 60°C.

A reaction solution was prepared by dissolving Fe(NO3) ₃ ㅇ9H ₂ O in a mixed aqueous solution of sulfuric acid and hydrogen peroxide at a concentration of 12.5 mM. The volume ratio of sulfuric acid and hydrogen peroxide in the mixed aqueous solution was 3: 1, and the total volume of sulfuric acid and hydrogen peroxide in the mixed aqueous solution was 0.1% by volume. The washed NF was immersed in the reaction solution for 1 hour and recovered to prepare an OER electrode. The prepared OER electrode was washed with ethanol and water, and dried in a vacuum oven at 60° C. overnight.

(Example 2)

A standard three-electrode cell was prepared using the OER electrode prepared in Example 1. In a standard three-electrode cell, a Pt coil was used as a counter electrode, Hg/HgO (1M NaOH) was used as a reference electrode, and a 1.0 M KOH solution (pH=14) was used as an alkaline electrolyte.

(Comparative Example 1)

An OER electrode was prepared in the same manner as in Example 1, except that water was used instead of the mixed aqueous solution when preparing the reaction solution.

(Comparative Example 2)

An OER electrode was prepared in the same manner as in Example 1, except that the washed NF was added to the mixed aqueous solution instead of the reaction solution in which Fe(NO3) ₃ ㅇ9H ₂ O was dissolved in the mixed aqueous solution.

(Comparative Example 3)

An OER electrode was prepared in the same manner as in Example 1, except that washed NF was added to water instead of the reaction solution.

(Comparative Example 4)

A RuO ₂ OER electrode was manufactured using a drop casting method. Specifically, RuO ₂ nanoparticles were dispersed in 0.84 g H ₂ O, and 0.38 g of IPA and 0.33 g of 5 wt% Nafion solution were added and stirred to prepare a slurry. The prepared slurry was dropped on both sides of the washed nickel foam (1x1cm ² ) and dried in a vacuum oven at 60° C. overnight, to prepare an OER electrode loaded with RuO ₂ nanoparticles at 0.2 mg/cm ² .

(Comparative Example 5)

The OER electrode was prepared in the same manner as in Example 1, except that Fe(NO3) ₃ ㅇ9H ₂ O was dissolved in an aqueous hydrogen peroxide solution of the same concentration as the mixed aqueous solution to prepare a comparative reaction solution, and washed NF was added to the comparative reaction solution. Was prepared.

(Comparative Example 6)

The OER electrode was prepared in the same manner as in Example 1, except that Fe(NO3) ₃ ㅇ9H ₂ O was dissolved in a sulfuric acid aqueous solution having the same concentration as the mixed aqueous solution to prepare a comparative reaction solution, and washed NF was added to the comparative reaction solution. Was prepared.

(Comparative Example 7)

An OER electrode was prepared in the same manner as in Example 1, except that the washed NF was added to an aqueous hydrogen peroxide solution having the same concentration as the mixed aqueous solution.

(Comparative Example 8)

An OER electrode was prepared in the same manner as in Example 1, except that the washed NF was added to an aqueous solution of sulfuric acid having the same concentration as the mixed aqueous solution.

Hereinafter, the OER electrode manufactured in Example 1 is collectively referred to as'NF-Fe-PS', the OER electrode manufactured in Comparative Example 1 is collectively referred to as'NF-Fe-W', and the OER electrode manufactured in Comparative Example 2 Is collectively referred to as'NF-PS', the OER electrode manufactured in Comparative Example 3 is collectively referred to as'NF-W', the OER electrode manufactured in Comparative Example 4 is collectively referred to as'RuO2', and the OER electrode manufactured in Comparative Example 5 The OER electrode is collectively referred to as'NF-Fe-H ₂ O ₂ ', the OER electrode manufactured in Comparative Example 6 is collectively referred to as'NF-Fe-H ₂ SO ₄ ', and the OER electrode manufactured in Comparative Example 7 is' It is collectively referred to as NF-H ₂ O ₂ ', and the OER electrode prepared in Comparative Example 8 is collectively referred to as'NF-H ₂ SO ₄ '. In addition, for comparison, a standard three-electrode cell was prepared in the same manner as in Example 2 using not only the electrode prepared in Comparative Examples, but also the washed NF as an OER electrode. When the cleaned NF itself is an OER electrode, it is collectively referred to as'NF'.

Analysis method: X-ray diffraction (XRD) was performed using an X-ray diffraction equipment (Rigaku Smartlab diffractometer), and a Cu Kα ray generated at 40kV and 15mA was used, and the scan speed was 4˚ per minute. Scanning electron microscope (SEM) analysis was performed using a Hitachi-SU8230 apparatus (3kV). Transmission electron microscopy analysis was performed by observing the cross section of the OER electrode vertically cut with a forced ion beam (FIB) using a Hitachi HF-3300 device (300kV acceleration voltage). Energy dispersion spectroscopy (EDS) and elemental mapping were performed using a scanning electron microscope analysis device and a transmission electron microscope analysis device. The EDS elemental analysis value may be performed in an area of at least 500 μmx500 μm or more in the OER electrode, and may be a value obtained by taking an average of 5 or more EDS analysis performed on an area of 500 μmx 500 μm or more at random. XPS (X-ray photoelectron spectroscopy) analysis was performed using an ESCALAB 250 XPS system equipped with an Al Kα (150W) source.

Electrochemical measurement: The potential value in a standard three-electrode cell was converted into a reversible hydrogen electrode reference potential value (vs.RHE) using the known equation in Equation 1. Equation 1: V(RHE) = 0.118 V + 0.059 V x pH + V _applied ; In Equation 1, V(RHE) is the reference potential value of the reversible hydrogen electrode, pH is the pH value of the electrolyte (=14), and V _applied is the applied voltage. When converting the voltage drop due to the solution resistance from the reversible hydrogen electrode reference potential value (vs.RHE) to the compensated potential (vs.RHE.IR _comp ), Equation 2 was used. Equation 2: V(RHE.IR _comp ) = V(RHE) -iRx0.85; In Equation 2, V(RHE.IR _comp ) means the potential for which the voltage drop due to the solution resistance is compensated, V(RHE) means the reversible hydrogen electrode reference potential calculated by Equation 1, and R is the electrochemical impedance It is the solution resistance value measured by spectroscopy, and i is the current value. Before measuring the electrochemical properties of the prepared OER electrode, 10 cyclic voltammetry (CV) measurements were performed. Cyclic voltammetry and linear sweep voltammetry (LSV) were measured at scan rates of 10mV/s and 20mV/s, and the cyclic voltammetry measurement result performed 85% voltage drop compensation according to Equation 2. I did. The Tafel plot was calculated from the measurement results of the linear perimeter method according to Equation 3. Equation 3: η = bㅇlog(j/j ₀ ); η is the overvoltage, b is the Tafel slope, j is the current density, and j ₀ is the exchange current density. The electrochemical impedance (ESI) spectrum was measured in the range of 102-106 Hz with an AC voltage of 10 mV amplitude. CP (Chronopotentiometric) measurement was performed in the range of 10mA/cm ² or 10-200mA/cm ² stepwise. To calculate the double-layer charge capacity (C _dl ), cyclic voltammetry measurements were performed at various speeds, and calculated using the difference between the anode (j _a ) and the cathode current (j _c ) at 0.65V.

1 is a NF-Fe-W (Fig. 1 (d) to (f)), NF-Fe-PS (Fig. 1 (g) to (i)) of NF (Fig. 1 (a) to (c)) This is a scanning electron microscope photograph of the surface.

As can be seen from Figure 1, it can be seen that the NF itself has a very smooth and clean surface. However, looking at NF-Fe-W and NF-Fe-PS reacted with Fe ³⁺ , it can be seen that during the corrosion reaction, Fe ions are deposited as hydroxide and a rough surface is formed. In particular, when looking at the NF-Fe-PS prepared in Example, particles having a diameter of about 10-30 nm are aggregated, but it can be seen that a rough surface layer having a porous agglomerated structure with empty spaces formed between the particles is formed, and the particles are aggregated. It can be seen that secondary particles were also formed.

FIG. 2 is a transmission electron microscope observation photograph of a cross section of NF-Fe-PS (FIGS. 2(a) to (c) and elemental mapping results of particles deposited on the nickel foam surface (FIG. 2(d) to (g))). It can be seen from the results of the transmission electron microscope of Fig. 2 that amorphous particles are aggregated to form secondary particles, in addition, Ni mapping of Fig. 2(e) and Fe of Fig. 2(f) Mapping, O mapping in Fig. 2(g), and mapping results of Ni, Fe and O in Fig. 2(d) show that the fine particles deposited on the nickel foam surface are iron hydroxides that do not contain nickel, and Fe ³ It can be seen that ⁺ is reduced and deposited into iron hydroxide.

3 is a diagram showing the XPS measurement results of each of NF-Fe-PS, NF-Fe-W, and NF, FIG. 3(a) is a full spectrum, FIG. 3(b) is a Ni 2p spectrum, and FIG. 3(c) ) Is a Fe 2p spectrum, Figure 3 (d) is a diagram showing the O 1s spectrum.

Looking at the XPS spectrum of NF, it can be seen that the surface of the nickel foam is covered with NiO by surface passivation. Looking at NF-Fe-PS and NF-Fe-W in FIG. 3(b), in the case of NF-Fe-PS prepared in the example, the peak of Ni ²⁺ (855.2 eV) increased significantly and Ni ⁰ ( 852.3 eV) is detected in a very small amount, whereas in the case of NF-Fe-W, even if the peak of Ni ²⁺ (855.2 eV) increases, the Ni ⁰ peak only slightly decreases. Through this, it can be seen that the surface oxidation of the nickel foam is greatly promoted by the reaction solution containing both inorganic acid and hydrogen peroxide.In the case of NF-Fe-PS prepared in the examples, most of the Ni present on the surface is in an ionic state (Ni It can be seen that it exists as ²⁺ ). Looking at NF, NF-Fe-PS and NF-Fe-W in FIG. 3(c), Fe ³⁺ (~710.8 eV) and Fe ^4+, which were not present in NF, were both F-Fe-PS and NF-Fe-W. It can be seen that (~712.5 eV) is detected. In addition, it can be seen that in the case of NF-Fe-PS prepared in Example, a larger amount of Fe ⁴⁺ is detected than NF-Fe-W. 3(d), Ni-O (529.3 eV) was detected in NF, and M-OH (531.05 eV) and Fe-O (529.7 eV) were detected in NF-Fe-PS and NF-Fe-W. You can see that it is. In addition, in the case of NF-Fe-PS, M-OH forms the main peak and Fe-O is present in a very small amount, indicating that Fe ions are mainly reduced in the form of hydroxide. In the case of NF-Fe-W, the Fe-O peak It can be seen that Fe ions tend to be reduced mainly in the form of oxides (Fe-O).

4 is a diagram showing the XPS measurement results of each of NF-Fe-H ₂ O ₂ and NF-Fe-H ₂ SO ₄ , FIG. 4(a) is a full spectrum, FIG. 4(b) is a Ni 2p spectrum, Fig. 4(c) is a view showing an Fe 2p spectrum, and Fig. 4(d) is a view showing an O 1s spectrum.

As can be seen from Figure 4, it can be seen that the Ni ⁰ peak is significantly reduced in both NF-Fe-H ₂ O ₂ and NF-Fe-H ₂ SO ₄ , and oxidation of nickel (Ni ² It can be seen that the formation of ⁺ ) is promoted. In addition, it can be seen that NF-Fe-H ₂ SO ₄ has a broad and asymmetric Fe 2p3/2 peak by Fe3+ and Fe4+ similar to NF-Fe-PS. In addition, in the case of NF-Fe-H ₂ SO ₄ , it can be confirmed that an O 1s peak similar to NF-Fe-PS in which M-OH is mainly detected is detected. In the case of NF-Fe-H ₂ O ₂ , it can be seen that various bonds such as MO (~529.7 eV), M-OH (~530.9 eV) and M-OOH (532.4 eV) are detected, especially Fe oxide (Fe- It can be seen that the formation of O) was very promoted.

5 is a diagram showing the results of X-ray diffraction measurements of NF, NF-Fe-PS, NF-Fe-H ₂ O ₂ , and NF-Fe-H ₂ SO ₄ . In FIG. 5, the peak detected at 2θ 40 to 80° is a nickel peak due to NF. In the case of NF-Fe-PS, it can be seen that there is a broad peak due to amorphous fine particles deposited on the nickel foam surface at 2θ 22°. However, in the case of NF-Fe-H ₂ O ₂ and NF-Fe-H ₂ SO ₄ , it was confirmed that the broad peak at 2θ 22° did not appear.

Table 1 is a table summarizing the elemental composition (atomic %) of each OER electrode prepared in Examples and Comparative Examples organized based on the XPS measurement results.

(Table 1)

As can be seen from Table 1, in the case of NF, it can be seen that most of the surface is covered with NiO, and in the case of NF-Fe-W, it contains about 10 atomic% Fe, but in the case of NF-Fe-PS, about 5 atomic% Fe It can be seen that it contains. In addition, it can be seen that NF-Fe-H ₂ O ₂ contains the largest amount of oxygen, but NF-Fe-H ₂ SO ₄ contains the smallest amount of oxygen.

From the XPS results of FIGS. 3 to 4 and the results of Table 1, the NF-Fe-PS prepared in the Example had very strong Fe-OH and Fe ⁴⁺ species due to the synergistic effect of hydrogen peroxide and sulfuric acid, an inorganic acid. You can see that it develops.

6 is a diagram showing the measurement of the electrochemical activity of each OER electrode by using NF, RuO ₂ , NF-Fe-W, NF-Fe-PS, NF-Fe-H2SO4, and NF-Fe-H2O2 as OER electrodes. In detail, FIG. 6(a) is a diagram showing the result of LVS measurement (10mV/s, iR compensated RHE) for each OER electrode, and FIG. 6(b) is a diagram showing a Tafel plot for each OER electrode. In this case, the potential in FIG. 6A is a (reference) potential value compared to the reversible hydrogen electrode in which the iR voltage drop is compensated.

As can be seen from FIG. 6, the NF-Fe-PS prepared in Example exhibits an overpotential of 245 mV at 10 mA/cm ² and has a Tafel slope of 82.9 mV/dec, indicating that it has the most excellent OER activity. I can. This is a far superior activity than OER electrodes using RuO ₂ nanoparticles known as state of the art. In addition, looking at the influence of the medium on the OER activity when introducing Fe ³⁺ into the nickel foam, it can be seen that the medium containing sulfuric acid and hydrogen peroxide in the examples significantly improved OER activity than sulfuric acid alone or hydrogen peroxide alone. In addition, it can be seen that the sulfuric acid alone medium improves the OER activity than the hydrogen peroxide alone medium, which can be interpreted as a relatively large amount of tetravalent Fe and MO and M-OOH species. In addition, a part to be noted is the Tafel slope in the Tafel plot of FIG. 6(b), and the Tafel slope is a measure of catalytic activity. In Figure 6(b), when water is the reaction medium, the Tafel slope is lower than that of sulfuric acid alone or hydrogen peroxide alone, but in the case of NF-Fe-PS in which Fe ³⁺ is introduced in a medium containing both sulfuric acid and hydrogen peroxide, NF- It can be seen that it has a lower Tafel slope than Fe-W. This is the result of showing a synergistic effect by the inorganic acid of sulfuric acid and hydrogen peroxide water when Fe ³⁺ is introduced into the nickel foam.

Although not necessarily limited to this analysis, the excellent activity of NF-Fe-PS is due to the synergy between the iron hydroxide fine particles and the Fe-modified nickel surface, and stably maintaining a large amount of surface -OH functional groups and a large amount of Fe ^4+. It can be interpreted, and it can be interpreted that the iron hydroxide particles act as an active site, and at the same time, due to the surface Fe-Ni, Fe ⁴⁺ remains stable even in OER, and high activity appears.

7 is a diagram showing the LVS measurement results (vs. iR compensated RHE) for each OER electrode of NF-PS, NF-W, NF-H ₂ SO ₄ , and NF-H ₂ O ₂ in which Fe is not introduced. . As can be seen from FIG. 7, it can be seen that when Fe is not introduced, it has almost similar activity to that of the pure nickel foam OER electrode (NF), and the medium (medium of the reaction solution) itself has little effect on the OER activity. Can be seen.

8 is an electrochemical impedance spectrum of each OER electrode of NF, NF-Fe-W, NF-Fe-PS, NF-Fe-H ₂ SO ₄ and NF-Fe-H ₂ O ₂ (Electrochemical Impedance spectra; EIS) Is a diagram showing an equivalent circuit, and Rs is a solution resistance, Rct is a charge transfer resistance, and Cdl is an electric double layer capacitor. As can be seen from FIG. 8, it can be seen that the NF-Fe-PS manufactured in Example has a lower charge transfer resistance (Rct) than any other OER electrode. This low Rct is advantageous because it can enhance OER activity.

9 is a diagram showing the CV measurement results (scan speed = 20 mV/s) of each OER electrode of NF, NF-Fe-W, NF-Fe-PS, NF-Fe-H2SO4, NF-Fe-H2O2, The inset drawing is an enlarged drawing in which some sections are enlarged. As can be seen from FIG. 9, it can be seen that the oxidation from Ni ²⁺ to Ni ³⁺ moves in the positive direction from about 1.44 V (NF) to about 1.47 V (NF-Fe-PS). The movement in the positive direction indicates an interaction between Ni and Fe species because Fe has a higher oxidation potential than Ni. NF-Fe-H2SO4 shows the highest current density at 1.46V due to its high content of Ni species, and in the case of NF-Fe-W (1.48V), it is known that the curve shifted in the positive direction by a large amount of Fe species. I can. The results of FIG. 9 are in good agreement with the Fe content in each OER electrode and the element ratio of Fe for each OER electrode shown in Table 1.

10 is a diagram showing a result of a durability test of NF-Fe-PS manufactured in Example. The durability test was performed for 500 hours at a fixed current density of 10 mA/cm ² , and the alkaline electrolyte (1.0 M KOH) was replaced every 100 hours. It was confirmed that the OER electrode of NF-Fe-PS has very good stability in that the voltage is maintained below 1.5V (270mV overvoltage) even after 500 hours of durability test.

11 is a diagram showing the XPS measurement results of each of NF-Fe-PS (Fresh in FIG. 11) before durability test and NF-Fe-PS (After in FIG. 11) after 500 hours durability test, FIG. 11(a) ) Is a full spectrum, FIG. 11(b) is a Ni 2p spectrum, FIG. 11(c) is a Fe 2p spectrum, and FIG. 11(d) is a view showing an O 1s spectrum.

As a result of XPS analysis of the tested OER electrode (NF-Fe-PS) after the durability test for 500 hours, it was confirmed that the atomic composition of Fe, Ni, and O is substantially the same as before the test in Table 1. , As can be seen from FIG. 11, Ni0 disappears by the OER reaction, the oxidation state of Fe changes from Fe ³⁺ to Fe ⁴⁺ , which is the OER activity center, and the Fe 2p 3/2 peak is a little wider. It can be seen that the bond disappears and only M-OH is detected.

12 is a diagram showing a result of testing the catalyst stability of NF-Fe-PS prepared in Example. The catalyst stability was carried out by increasing the current density stepwise to 10, 20, 30, 100 and 200 mA/cm ² at 1 hour intervals for 5 hours, and repeating this three times. As can be seen from Fig. 12, no performance degradation was observed even when performing three repetitions.

13 is a diagram showing the CV results of each OER electrode of NF, NF-Fe-W, NF-Fe-PS, and the scan speed is changed to 10, 20, 50, 100, or 200 mV/s for each OER electrode. It is a diagram (Fig. 13(d)) showing the measurement result and the difference in anode and cathode current density (Ja-Jc) according to the scan speed at 0.65V. The active site of the OER electrode can be evaluated through the double-layer capacitance (Cdl) value using CV. As can be seen from FIG. 13(d), the NF-Fe-PS prepared in the Example has a significantly higher Cdl of 1.4 μFcm ^-2 than NF-Fe-W (0.8 μFcm ^{- 2} ) and NF (0.4 μFcm ^-2 ). It can be seen that it has a value, and through this, it can be seen that NF-Fe-PS has a very high active surface area and high OER activity.

14 is a diagram showing an optical photograph and time-current (chronoamperometric) characteristics of a solar cell-water electrolysis system constructed so that water electrolysis is performed by power generated from a solar cell.

In order to perform water electrolysis by electric power generated from the solar cell, the solar cell-water electrolysis system was manufactured by connecting a commercial solar cell (Ф 59, 5V, 40 mA) and a two-electrode cell in series. In the two-electrode cell, the alkaline electrolyte was a 1.0 M KOH solution, and the counter electrode of the OER electrode prepared in Example 1 was a Pt coil. During light irradiation, a 300W Xe arc lamp equipped with an AM 1.5G filter was used as a light source, and the light intensity was adjusted to 1 SUN.

As can be seen from FIG. 14, it can be seen that a very high current density of about 23 to 24 mA/cm ² appears by the power supplied from the commercial solar cell under the light irradiation condition of 1 SUN, and any deterioration occurs for 10 hours. It can be seen that the OER performance is stably maintained without doing so.

As described above, the present invention has been described by specific matters and limited embodiments and drawings, but this is provided only to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is Those of ordinary skill in the relevant field can make various modifications and variations from this description.

Therefore, the spirit of the present invention is limited to the described embodiments and should not be defined, and all things that are equivalent or equivalent to the claims as well as the claims to be described later fall within the scope of the spirit of the present invention. .

Claims (18)

A first active metal substrate; And a surface layer in which fine particles having a diameter of 1 to 90 nm are irregularly agglomerated, but having porosity by irregular aggregation, wherein the fine particles include a hydroxide of a second active metal different from the first active metal, and the The microparticles are amorphous, the surface layer contains both a trivalent second active metal and a tetravalent second active metal, and a tetravalent second active metal calculated from X-ray photoelectron spectroscopy 2P _3/2 spectrum of the second active metal An oxygen generating reaction electrode having an atomic ratio of 0.2 or more of the second active metal of /3 valency.
delete The method of claim 1,
An oxygen generating reaction electrode in which the ratio of M-OH/MO calculated from the X-ray photoelectron spectroscopy O 1s spectrum of oxygen is 5 or more, using the metal selected from at least one of the first and second active metals as M. The method of claim 1,
By oxidation of the first active metal and reduction of the second active metal caused by the standard reduction potential difference between the first and second active metals, the surface layer is directly on the surface of the first active metal substrate (in-situ). ) Formed of an oxygen generating reaction electrode. The method of claim 1,
The composition of the second active metal in the elemental composition (atomic %) between the first active metal, the second active metal and oxygen as measured by X-ray photoelectron spectroscopy (XPS) is 3.5 to 10.0 atomic%, and the first The composition of the active metal is 16.0 to 30.0 atomic% of the oxygen generating reaction electrode. The method of claim 1,
The first active metal substrate is a first active metal foam (foam), foil (film), mesh (mesh), felt (felt) or a porous foil (perforated film) of the oxygen generating reaction electrode. delete The method of claim 1,
On the X-ray diffraction pattern using Cu Kα, in addition to the diffraction peak derived from the first active metal, an oxygen generating reaction electrode having a diffraction peak located in a region of 2θ 21 to 24°. The method according to any one of claims 1, 3 to 6, and 8,
The first active metal is Ni, and the second active metal is Fe, Mo, or Fe and Mo. The method of claim 9,
The oxygen generating reaction electrode is an oxygen generating reaction electrode having an overvoltage of 250 mV or less based on a current density of 10 mA/cm ² . The method of claim 9,
The oxygen generating reaction electrode is an oxygen generating reaction electrode having a Tafel slope of 84mV/decade or less. The method of claim 9,
An oxygen generating reaction electrode having a double layer capacitance value of 1.2 μFcm ^-2 or more, calculated by cyclic voltammetry. An apparatus comprising an electrochemical water decomposition cell comprising an oxygen generating reaction electrode according to any one of claims 1, 3 to 6, and 8. The method of claim 13,
The device further comprises a solar cell connected in series with the electrochemical water cracking cell. It is a method of manufacturing an oxygen generating reaction electrode according to any one of claims 1, 3 to 6, and 8,
A step of contacting a substrate of a first active metal; and a reaction solution containing a precursor of a second active metal different from the first active metal, an inorganic acid, and hydrogen peroxide having a higher standard reduction potential than the first active metal; Method for producing an oxygen generating reaction electrode. The method of claim 15,
The volume fraction occupied by the inorganic acid and hydrogen peroxide in the reaction solution is 0.05% to 3.00%. The method of claim 15,
The inorganic acid: hydrogen peroxide volume ratio is 0.5 to 10: 1, the method of producing an oxygen generating reaction electrode. The method of claim 15,
The inorganic acid is a method for producing an oxygen generating reaction electrode containing sulfuric acid.

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