Electrode material with self-supporting sandwich structure as well as preparation method and application of electrode material

Abstract

The invention belongs to the technical field of oxygen evolution electrode materials, and particularly discloses an electrode material of a self-supporting sandwich structure and a preparation method and application of the electrode material of the self-supporting sandwich structure. S2, according to the proportion, metal nickel salt, urea and ammonium fluoride are dissolved in water and stirred uniformly to obtain a mixed solution A, and metal cobalt salt, urea and ammonium fluoride are dissolved in water and stirred uniformly to obtain a mixed solution B; s3, transferring the mixed solution A into a high-pressure reaction kettle, and carrying out hydrothermal treatment on the mixed solution A and carbon fiber cloth; s4, carrying out hydrothermal treatment on the mixed solution B and nickel-carbon cloth; and S5, carrying out hydrothermal treatment on the mixed solution A and cobalt-nickel-carbon cloth to obtain the self-supporting sandwich structure electrode material. According to the electrode material with the self-supporting sandwich structure as well as the preparation method and the application of the electrode material, the preparation method simplifies the electrode preparation process and reduces the cost, and the prepared electrode material has relatively good oxygen evolution reaction performance and reduces the energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of oxygen evolution electrode materials, and in particular to an electrode material with a self-supporting sandwich structure, a preparation method thereof, and an application thereof. Background Art

[0002] The oxygen evolution reaction is an important half-reaction in new energy conversion and storage devices such as metal-air batteries and water electrolysis systems. However, the slow kinetics of the oxygen evolution reaction seriously hinders the large-scale application of these systems. Designing and developing efficient catalysts is the key to improving the efficiency of the oxygen evolution reaction. At present, some noble metal-based materials such as Ir and RuO2 are considered to be the most active oxygen evolution reaction catalysts, but their reserves are scarce and the cost is high. Therefore, efficient non-noble metal oxygen evolution electrode materials (catalysts) are of great practical significance for simplifying the design of electrolyzer systems, reducing the energy consumption of water electrolysis, and ultimately reducing the production cost of oxygen.

[0003] Transition metals are considered potential substitutes due to their environmental friendliness, rich reserves, and moderate overpotential. However, on the one hand, due to insufficient active sites and unsatisfactory adsorption strength for oxygen-containing intermediates, and on the other hand, due to their inherent semiconductor properties and weak electron conduction ability, the catalytic efficiency of transition metals still cannot meet the requirements of commercial applications.

[0004] In the prior art, during the preparation process of the electrode material, it is necessary to use an adhesive for coating, which not only makes the preparation process cumbersome, but also causes the coverage of active sites and the blockage of pores, resulting in a significant reduction in the electron conduction ability of the electrode material. Therefore, how to avoid the problem of the reduction of the self-performance of the electrode material caused by the adhesive coating still needs to be further explored. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrode material with a self-supporting sandwich structure, a preparation method thereof, and an application thereof. The preparation method simplifies the electrode preparation process, reduces costs, and the prepared electrode material has good oxygen evolution reaction performance and reduces energy consumption.

[0006] To achieve the above purpose, the present invention provides a preparation method of an electrode material with a self-supporting sandwich structure, including the following steps:

[0007] S1. Pretreatment of carbon fiber cloth;

[0008] S2. According to the proportion, dissolve metal nickel salt, urea, and ammonium fluoride in water and stir evenly to obtain a mixed solution A, and dissolve metal cobalt salt, urea, and ammonium fluoride in water and stir evenly to obtain a mixed solution B;

[0009] S3. Transfer the mixed solution A obtained in S2 to a high-pressure reaction kettle, put the carbon fiber cloth obtained in S1, and perform hydrothermal treatment to obtain nickel-carbon cloth;

[0010] S4. Transfer the mixed solution B obtained in S2 to a high-pressure reactor, put in the nickel-carbon cloth obtained in S3, and perform hydrothermal treatment to obtain cobalt-nickel-carbon cloth;

[0011] S5. Transfer the mixed solution A obtained in S2 to a high-pressure reactor, put in the cobalt-nickel-carbon cloth obtained in S4, and perform hydrothermal treatment to obtain a self-supporting sandwich-structured electrode material.

[0012] Preferably, S1 is specifically:

[0013] Cut the carbon fiber cloth into pieces, then soak it in 1M nitric acid solution for 6h, then wash it with deionized water and dry it to obtain the pretreated carbon fiber cloth.

[0014] Preferably, in S2, the mixed solution A includes 0.01M - 0.10M metal nickel salt and 0.05M - 1.00M regulator;

[0015] The mixed solution B includes 0.01M - 0.10M metal cobalt salt and 0.05M - 1.00M regulator.

[0016] Preferably, the regulator is a mixture of urea and ammonium fluoride, and the molar ratio of urea to ammonium fluoride is 1:1.

[0017] Preferably, in S2, the metal cobalt salt is one of cobalt nitrate or cobalt hydrochloride.

[0018] Preferably, in S2, the metal nickel salt is one of nickel nitrate or nickel hydrochloride.

[0019] Preferably, in S3, the hydrothermal treatment is specifically:

[0020] Treat at a hydrothermal temperature of 100°C - 180°C for 5h - 40h, take it out and perform ultrasonic washing 3 times with deionized water and absolute ethanol respectively, and then dry it.

[0021] Preferably, in S3, the high-pressure reactor uses a polytetrafluoroethylene reactor liner.

[0022] The present invention also provides a self-supporting sandwich-structured electrode material, including a carbon fiber cloth and nickel layers, cobalt layers and nickel layers successively coated on the surface of the carbon fiber cloth.

[0023] The present invention also provides an application of the self-supporting sandwich-structured electrode material in the oxygen evolution reaction.

[0024] Therefore, the present invention adopts the above-mentioned self-supporting sandwich-structured electrode material, its preparation method and application, and the beneficial effects are as follows:

[0025] (1) The oxygen evolution electrode material prepared by the present invention has a nickel-cobalt-nickel layered, three-dimensional porous and self-supporting sandwich structure. The preparation method simplifies the electrode preparation process, is easy to operate, reduces costs, is conducive to large-scale industrial application, and has high popularization potential. Moreover, no binder is used, ensuring rapid charge transfer and exposing more active sites.

[0026] (2) The oxygen evolution electrode material prepared by the present invention utilizes the coupling effect between layers of the sandwich structure, the three-dimensional porous structure and the self-supporting carbon fiber cloth without using a binder. It can not only effectively regulate the electronic structure and surface properties of the electrocatalyst, enhancing the electron conduction ability; but also expose abundant active sites, and the three-dimensional porous structure is conducive to the penetration of the electrolyte and the separation of gas bubble products. The abundant active sites and the contact with the reactants are beneficial to the adsorption and conversion of the reactants at the active sites, promoting the kinetic process of the oxygen evolution reaction. The two work together to achieve excellent oxygen evolution performance.

[0027] (3) The electrode material prepared by the present invention has good oxygen evolution reaction performance. A current density of 10 mA / cm² can be achieved at an overpotential of 212 mV, which is superior to most of the transition metal catalysts in the prior art, reducing energy consumption and solving problems such as high voltage required for the oxygen evolution process and large energy consumption. 2

[0028] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the linear sweep voltammogram of the self-supporting sandwich-structured electrode material of the present invention;

[0030] Figure 2 is the overpotential result of the self-supporting sandwich-structured electrode material of the present invention at 10 mA / cm² -2 and 50 mA / cm² -2 ;

[0031] Figure 3 is the Tafel slope result of the self-supporting sandwich-structured electrode material of the present invention;

[0032] Figure 4 is the cross-sectional scanning electron micrograph of Example 3 of the self-supporting sandwich-structured electrode material of the present invention;

[0033] Figure 5 is the cross-sectional element distribution diagram of Example 3 of the self-supporting sandwich-structured electrode material of the present invention;

[0034] Figure 6It is the planar scanning electron micrograph of the third embodiment of the self-supporting sandwich-structured electrode material of the present invention. Detailed implementation manners

[0035] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0036] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs.

[0037] Embodiment 1

[0038] A self-supporting sandwich-structured electrode material, and its preparation method is as follows:

[0039] S1. Pretreatment of carbon fiber cloth:

[0040] Cut the carbon fiber cloth into cloth pieces with a size of 1 cm × 3 cm, then soak them in a 1 M nitric acid solution for 6 h, wash them with deionized water and then dry them for standby to obtain the pretreated carbon fiber cloth.

[0041] S2. Dissolve 0.1454 g of nickel nitrate hexahydrate, 0.1502 g of urea and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution A with a concentration of 0.025 M of metal nickel salt and 0.125 M of regulator. Dissolve 0.1455 g of cobalt nitrate hexahydrate, 0.1502 g of urea and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution B with a concentration of 0.025 M of metal cobalt salt and 0.125 M of regulator.

[0042] S3. Transfer 20 mL of the mixed solution A to the inner lining of a polytetrafluoroethylene reaction kettle, put the carbon fiber cloth obtained in S1, treat it at a hydrothermal temperature of 100 °C for 5 h, take it out and ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain nickel-carbon cloth;

[0043] S4. Transfer 20 mL of the mixed solution B to the inner lining of a polytetrafluoroethylene reaction kettle, put the nickel-carbon cloth obtained in S3, treat it at a hydrothermal temperature of 100 °C for 5 h, take it out and ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain cobalt-nickel-carbon cloth;

[0044] S5. Transfer 20 mL of the mixed solution A to the inner lining of a polytetrafluoroethylene reaction kettle, put the cobalt-nickel-carbon cloth obtained in S4, treat it at a hydrothermal temperature of 100 °C for 5 h, take it out and ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain the self-supporting sandwich-structured electrode material.

[0045] Embodiment 2

[0046] An electrode material with a self-supporting sandwich structure, and its preparation method is as follows:

[0047] S1. Pretreatment of carbon fiber cloth:

[0048] Cut the carbon fiber cloth into cloth pieces with a size of 1 cm × 3 cm, then soak them in 1 M nitric acid solution for 6 h, wash them with deionized water and then dry them for standby to obtain the pretreated carbon fiber cloth.

[0049] S2. Dissolve 0.1454 g of nickel nitrate hexahydrate, 0.1502 g of urea and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution A of metal nickel salt with a concentration of 0.025 M and a regulator with a concentration of 0.125 M. Dissolve 0.1455 g of cobalt nitrate hexahydrate, 0.1502 g of urea and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution B of metal cobalt salt with a concentration of 0.025 M and a regulator with a concentration of 0.125 M.

[0050] S3. Transfer 20 mL of the mixed solution A to the inner lining of a polytetrafluoroethylene reaction kettle, put in the carbon fiber cloth obtained in S1, treat it at a hydrothermal temperature of 100 °C for 10 h, take it out and ultrasonically wash it 3 times with deionized water and anhydrous ethanol respectively, and then dry it to obtain nickel-carbon cloth;

[0051] S4. Transfer 20 mL of the mixed solution B to the inner lining of a polytetrafluoroethylene reaction kettle, put in the nickel-carbon cloth obtained in S3, treat it at a hydrothermal temperature of 100 °C for 10 h, take it out and ultrasonically wash it 3 times with deionized water and anhydrous ethanol respectively, and then dry it to obtain cobalt-nickel-carbon cloth;

[0052] S5. Transfer 20 mL of the mixed solution A to the inner lining of a polytetrafluoroethylene reaction kettle, put in the cobalt-nickel-carbon cloth obtained in S4, treat it at a hydrothermal temperature of 100 °C for 10 h, take it out and ultrasonically wash it 3 times with deionized water and anhydrous ethanol respectively, and then dry it to obtain the self-supporting sandwich structure electrode material.

[0053] Example 3

[0054] An electrode material with a self-supporting sandwich structure, and its preparation method is as follows:

[0055] S1. Pretreatment of carbon fiber cloth:

[0056] Cut the carbon fiber cloth into cloth pieces with a size of 1 cm × 3 cm, then soak them in 1 M nitric acid solution for 6 h, wash them with deionized water and then dry them for standby to obtain the pretreated carbon fiber cloth.

[0057] S2. Dissolve 0.1454 g of nickel nitrate hexahydrate, 0.1502 g of urea, and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution A of metal nickel salt with a concentration of 0.025 M and a regulator with a concentration of 0.125 M. Dissolve 0.1455 g of cobalt nitrate hexahydrate, 0.1502 g of urea, and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution B of metal cobalt salt with a concentration of 0.025 M and a regulator with a concentration of 0.125 M.

[0058] S3. Transfer 20 mL of the mixed solution A to the inner lining of a polytetrafluoroethylene reaction kettle, put in the carbon fiber cloth obtained in S1, treat it at a hydrothermal temperature of 100 °C for 20 h, take it out, and ultrasonically wash it 3 times with deionized water and anhydrous ethanol respectively, then dry it to obtain nickel-carbon cloth.

[0059] S4. Transfer 20 mL of the mixed solution B to the inner lining of a polytetrafluoroethylene reaction kettle, put in the nickel-carbon cloth obtained in S3, treat it at a hydrothermal temperature of 100 °C for 20 h, take it out, and ultrasonically wash it 3 times with deionized water and anhydrous ethanol respectively, then dry it to obtain cobalt-nickel-carbon cloth.

[0060] S5. Transfer 20 mL of the mixed solution A to the inner lining of a polytetrafluoroethylene reaction kettle, put in the cobalt-nickel-carbon cloth obtained in S4, treat it at a hydrothermal temperature of 100 °C for 20 h, take it out, and ultrasonically wash it 3 times with deionized water and anhydrous ethanol respectively, then dry it to obtain a self-supporting sandwich-structured electrode material.

[0061] Example 4

[0062] A self-supporting sandwich-structured electrode material, and its preparation method is as follows:

[0063] S1. Pretreatment of carbon fiber cloth:

[0064] Cut the carbon fiber cloth into cloth pieces with a size of 1 cm × 3 cm, then soak it in 1 M nitric acid solution for 6 h, wash it with deionized water and dry it for standby to obtain the pretreated carbon fiber cloth.

[0065] S2. Dissolve 0.1454 g of nickel nitrate hexahydrate, 0.1502 g of urea, and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution A of metal nickel salt with a concentration of 0.025 M and a regulator with a concentration of 0.125 M. Dissolve 0.1455 g of cobalt nitrate hexahydrate, 0.1502 g of urea, and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution B of metal cobalt salt with a concentration of 0.025 M and a regulator with a concentration of 0.125 M.

[0066] S3. Transfer 20 mL of the mixed solution A into the PTFE reactor liner, place the carbon fiber cloth obtained in S1, and treat it at a hydrothermal temperature of 100 °C for 40 h. After taking it out, ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain nickel-carbon cloth;

[0067] S4. Transfer 20 mL of the mixed solution B into the PTFE reactor liner, place the nickel-carbon cloth obtained in S3, and treat it at a hydrothermal temperature of 100 °C for 40 h. After taking it out, ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain cobalt-nickel-carbon cloth;

[0068] S5. Transfer 20 mL of the mixed solution A into the PTFE reactor liner, place the cobalt-nickel-carbon cloth obtained in S4, and treat it at a hydrothermal temperature of 100 °C for 40 h. After taking it out, ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain a self-supporting sandwich-structured electrode material.

[0069] Comparative Example 1

[0070] An electrode material with a pure nickel self-supporting sandwich structure is prepared as follows:

[0071] S1. Pretreatment of carbon fiber cloth:

[0072] Cut the carbon fiber cloth into cloth pieces with a size of 1 cm × 3 cm, then soak it in 1 M nitric acid solution for 6 h, wash it with deionized water and then dry it for standby to obtain the pretreated carbon fiber cloth.

[0073] S2. Dissolve 0.1454 g of nickel nitrate hexahydrate, 0.1502 g of urea and 0.0926 g of ammonium fluoride in 20 mL of water, stir evenly to obtain a mixed solution A with a concentration of 0.025 M of metal nickel salt and 0.125 M of regulator.

[0074] S3. Transfer 20 mL of the mixed solution A into the PTFE reactor liner, place the carbon fiber cloth obtained in S1, and treat it at a hydrothermal temperature of 100 °C for 20 h. After taking it out, ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain nickel-carbon cloth;

[0075] S4. Transfer 20 mL of the mixed solution A into the PTFE reactor liner, place the nickel-carbon cloth obtained in S3, and treat it at a hydrothermal temperature of 100 °C for 20 h. After taking it out, ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and then dry it to obtain nickel-nickel-carbon cloth;

[0076] S5. Transfer 20 mL of the mixed solution A into the inner lining of a polytetrafluoroethylene reaction kettle, place the nickel-nickel-carbon cloth obtained in S4, treat it at a hydrothermal temperature of 100 °C for 20 h, take it out, wash it ultrasonically 3 times with deionized water and absolute ethanol respectively, and dry it to obtain a self-supporting sandwich-structured electrode material.

[0077] Experimental tests

[0078] The electrode materials prepared in Examples 1 to 4 and Comparative Example 1 were used to conduct electrocatalytic performance tests by linear sweep voltammetry. Using an electrochemical workstation, a three-electrode system was adopted during the test. That is, the prepared electrode material was the working electrode, Pt was the counter electrode, Hg / HgO was the reference electrode, and 1 mol / L KOH solution was used as the electrolyte, with a scanning rate of 10 mV / s. The test results are as Figure 1 shown.

[0079] It can be Figure 1 seen that the prepared sandwich-structured catalysts all showed good oxygen evolution reaction performance. At the same overpotential, the current density of the catalyst prepared for 20 h was the largest, indicating that its oxygen evolution reaction performance was the best.

[0080] The overpotential results at 10 mA / cm -2 and 50 mA / cm -2 are as Figure 2 shown.

[0081] It can be Figure 2 seen that the overpotentials of the prepared sandwich-structured catalysts at 10 mA / cm -2 and 50 mA / cm -2 were lower than those of the pure nickel catalyst, indicating that the heterogeneous interfaces and three-dimensional porous structures existing in the sandwich structure can not only effectively regulate the electronic structure and surface characteristics of the electrocatalyst and improve the electron conduction ability, but also expose abundant active sites. Moreover, the three-dimensional porous structure is conducive to the penetration of the electrolyte and the separation of gas bubble products. The abundant active sites and the contact of reactants are beneficial to the adsorption and conversion of reactants at the active sites, promoting the kinetic process of the oxygen evolution reaction. The two work together to achieve excellent oxygen evolution performance.

[0082] The Tafel slope results are as Figure 3 shown.

[0083] It can be Figure 3 seen that among the prepared sandwich-structured catalysts, the Tafel slope of the catalyst prepared for 20 h was 150 mV / dec, while the Tafel slope of the pure nickel catalyst was 188 mV / dec, indicating that the sandwich-structured catalyst had a faster oxygen evolution reaction kinetic performance.

[0084] The electrode material prepared in Example 3 was used for structural analysis. The cross-sectional scanning electron micrograph is as shown in Figure 4 and the elemental distribution map is as shown in Figure 5 and the planar scanning electron micrograph is as shown in Figure 6 .

[0085] It can be seen from Figures 4 - 6 that nickel and cobalt grow uniformly on the carbon fiber cloth substrate, and the cross-sectional electron micrograph and elemental distribution clearly show that the nickel-cobalt-nickel sandwich structure has been successfully prepared, proving the existence of a heterogeneous interface and a three-dimensional porous structure in the catalyst.

[0086] Therefore, the present invention adopts the above-mentioned electrode material with a self-supporting sandwich structure, its preparation method and application. The preparation method simplifies the electrode preparation process and reduces costs. The prepared electrode material has good oxygen evolution reaction performance and reduces energy consumption.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of an electrode material with a self-supporting sandwich structure, characterized in that, It includes the following steps: S1. Pretreatment of carbon fiber cloth; S2. Dissolve metal nickel salt, urea and ammonium fluoride in water in proportion and stir evenly to obtain mixed solution A, and dissolve metal cobalt salt, urea and ammonium fluoride in water and stir evenly to obtain mixed solution B; S3. Transfer the mixed solution A obtained in S2 to a high-pressure reaction kettle, put the carbon fiber cloth obtained in S1, carry out hydrothermal treatment to obtain nickel-carbon cloth; S4. Transfer the mixed solution B obtained in S2 to a high-pressure reaction kettle, put the nickel-carbon cloth obtained in S3, carry out hydrothermal treatment to obtain cobalt-nickel-carbon cloth; S5. Transfer the mixed solution A obtained in S2 to a high-pressure reaction kettle, put the cobalt-nickel-carbon cloth obtained in S4, carry out hydrothermal treatment to obtain a self-supporting sandwich-structured electrode material.

2. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 1, characterized in that, Specifically, S1 is: Cut the carbon fiber cloth into pieces, then soak it in 1M nitric acid solution for 6h, then wash it with deionized water and dry it to obtain the pretreated carbon fiber cloth.

3. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 1, characterized in that, In S2, the mixed solution A includes 0.01M - 0.10M metal nickel salt and 0.05M - 1.00M regulator; The mixed solution B includes 0.01M - 0.10M metal cobalt salt and 0.05M - 1.00M regulator.

4. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 3, characterized in that, The regulator is a mixture of urea and ammonium fluoride, and the molar ratio of urea to ammonium fluoride is 1:

1.

5. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 1, characterized in that, In S2, the metal cobalt salt is one of cobalt nitrate or cobalt hydrochloride.

6. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 1, characterized in that, In S2, the metal nickel salt is one of nickel nitrate or nickel hydrochloride.

7. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 1, characterized in that, In S3, the hydrothermal treatment is specifically: Treat at a hydrothermal temperature of 100°C - 180°C for 5h - 40h, take it out and ultrasonically wash it 3 times with deionized water and absolute ethanol respectively, and dry it.

8. The preparation method of an electrode material with a self-supporting sandwich structure according to claim 1, characterized in that, In S3, the high-pressure reaction kettle uses a polytetrafluoroethylene reaction kettle liner.

9. A self-supporting sandwich-structured electrode material prepared by the preparation method of the self-supporting sandwich-structured electrode material according to any one of claims 1-8, characterized in that, It includes a carbon fiber cloth and nickel layers, cobalt layers and nickel layers successively coated on the surface of the carbon fiber cloth.

10. Application of the self-supporting sandwich-structured electrode material prepared by the preparation method of the self-supporting sandwich-structured electrode material according to any one of claims 1 - 8 or the self-supporting sandwich-structured electrode material according to claim 9 in the oxygen evolution reaction.

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