Preparation method and application of bimetallic phosphate oxygen evolution electrode

Abstract

The invention discloses a preparation method and application of a bimetallic phosphate oxygen evolution electrode. The preparation method of the bimetallic phosphate oxygen evolution electrode comprises the following steps: cleaning a nickel substrate in an alkaline solution to remove oil, and cleaning the nickel substrate with pure water; soaking the cleaned nickel substrate in an acid solution, cleaning the nickel substrate with pure water, and placing the nickel substrate in the pure water for later use; the nickel substrate placed in the pure water serves as a cathode, two pure nickel materials are placed on the two sides of the nickel substrate to serve as two anodes, and electro-deposition is conducted on the nickel substrate in a bimetallic phosphate solution; and washing an electrode obtained after electrodeposition of the nickel substrate, and drying to obtain the bimetallic phosphate electrode. According to the preparation method, the adsorption free energy of a catalytic layer on the surface of the bimetallic phosphate oxygen evolution electrode on a reaction intermediate is optimized through the synergistic electronic effect of two metals, so that the intrinsic activity of oxygen evolution reaction is improved, meanwhile, a relatively stable catalytic layer structure is formed, and the stability of the bimetallic phosphate oxygen evolution electrode in the oxygen evolution process is improved.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, specifically relating to a method for preparing a bimetallic phosphate oxygen evolution electrode and its application. Background Technology

[0002] With the increasing global demand for clean energy and sustainable development, hydrogen energy, as a zero-carbon, highly efficient secondary energy source, has received widespread attention for its development and utilization. Among numerous hydrogen production technologies, alkaline water electrolysis has become one of the mainstream technologies due to its relatively mature technology, low cost, and scalability. The water electrolysis process involves two half-reactions: the hydrogen evolution reaction at the cathode and the oxygen evolution reaction at the anode. Among these, the oxygen evolution reaction is a complex process involving the transfer of four electrons, with slow kinetics and high overpotential, becoming a bottleneck restricting the improvement of the overall water electrolysis efficiency.

[0003] To reduce the overpotential of the oxygen evolution reaction (OER) and improve energy conversion efficiency, developing high-performance and highly stable OER electrocatalysts is crucial. Currently, noble metal-based catalysts (such as IrO2 and RuO2) are considered the best performing OER catalysts. However, the scarcity and high cost of these noble metal materials greatly limit their application in large-scale industrial hydrogen production.

[0004] Transition metal-based materials (such as phosphides, sulfides, and hydroxides) have become a research hotspot due to their low cost, abundant reserves, and potentially excellent catalytic performance. Traditional phosphate electrode preparation methods are complex, with many synthetic routes involving high-temperature phosphating, hydrothermal / solvothermal processes. These steps are cumbersome, energy-intensive, and may use toxic phosphorus sources, hindering large-scale, environmentally friendly production. Furthermore, traditional powdered catalysts require coating the current collector with polymer binders (such as Nafion) to form the electrode. The introduction of binders can cover some active sites, increasing interfacial resistance. During long-term operation, especially under high current density and strongly alkaline conditions, the catalyst is prone to detachment from the substrate due to bubble erosion, severely affecting the electrode's stability and lifespan.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a bimetallic phosphate oxygen evolution electrode, which can form a stable catalytic layer structure on the surface of a nickel substrate, thereby improving the stability of the oxygen evolution electrode during the oxygen evolution process.

[0007] To achieve the above objectives, a specific embodiment of the present invention provides a method for preparing a bimetallic phosphate oxygen evolution electrode, comprising: cleaning and degreasing a nickel substrate in an alkaline solution and rinsing it with pure water; immersing the cleaned nickel substrate in an acidic solution and rinsing it with pure water, and placing it in pure water for later use; using the nickel substrate placed in pure water as a cathode, placing two pure nickel materials on both sides of the nickel substrate as two anodes, and performing electrodeposition on the nickel substrate in a bimetallic phosphate solution; rinsing the electrode obtained after electrodeposition on the nickel substrate and drying it to obtain a bimetallic phosphate electrode.

[0008] In one or more embodiments of the present invention, the bimetallic phosphate solution comprises a phosphate solution, at least two metal salt solutions, and a stabilizer.

[0009] In one or more embodiments of the present invention, the phosphate solution is selected from one or more of sodium hypophosphite solution, sodium phosphite solution, or sodium phosphate solution; and / or, the concentration of the phosphate solution is 0.3 to 0.7 M.

[0010] In one or more embodiments of the present invention, the metal salt solution is selected from two of nickel salt solution, cobalt salt solution and iron salt solution; and / or, the stabilizer is selected from one or more of sodium citrate, ethylenediaminetetraacetic acid and ascorbic acid.

[0011] In one or more embodiments of the present invention, the nickel salt solution is selected from nickel sulfate, nickel chloride or nickel nitrate; and / or, the concentration of the nickel salt solution is 20 to 50 mM.

[0012] In one or more embodiments of the present invention, the cobalt salt solution is selected from cobalt sulfate, cobalt chloride or cobalt nitrate; and / or, the concentration of the cobalt salt solution is 10 to 30 mM.

[0013] In one or more embodiments of the present invention, the iron salt solution is selected from ferric sulfate, ferric chloride or ferric nitrate; and / or, the concentration of the iron salt solution is 10 to 30 mM.

[0014] In one or more embodiments of the present invention, the nickel substrate is selected from nickel mesh, nickel foam, and nickel felt.

[0015] In one or more embodiments of the present invention, the current density of the electrodeposition is 10 to 30 mA / cm². 2 The time is 20 to 60 minutes, and the temperature is 20°C to 30°C.

[0016] In one or more embodiments of the present invention, the alkaline solution is one of soapy water, 30% KOH and metal cleaning solution; and / or, the acidic solution is an HCl solution; and / or, the concentration of the acidic solution is 1 to 3M.

[0017] In one or more embodiments of the present invention, the nickel-based substrate is ultrasonically cleaned in an alkaline solution for 10 to 30 minutes; and / or, the nickel-based substrate is immersed in an acidic solution for 5 to 10 minutes.

[0018] Another specific embodiment of the present invention provides a bimetallic phosphate oxygen evolution electrode prepared using the preparation method described in any of the above embodiments.

[0019] Another specific embodiment of the present invention provides an application of the above-mentioned bimetallic phosphate oxygen evolution electrode in the field of alkaline water electrolysis for hydrogen production.

[0020] Compared with existing technologies, the bimetallic phosphate oxygen evolution electrode of this invention utilizes bimetallic phosphate as the active material and employs a one-step electrodeposition method to directly grow the active material on a nickel substrate, forming a strong chemical bond. This avoids the use of binders, ensuring excellent electronic conduction and structural stability. The entire preparation process does not require high temperature and high pressure; the phosphating process is carried out under mild liquid phase conditions. The process is simple, safe, and low-cost, making it suitable for large-scale production. Furthermore, this preparation method optimizes the adsorption free energy of the catalytic layer on the surface of the bimetallic phosphate oxygen evolution electrode for reaction intermediates through the synergistic electronic effect of the two metals, thereby enhancing the intrinsic activity of the oxygen evolution reaction. Simultaneously, it forms a more stable catalytic layer structure, improving the stability of the bimetallic phosphate oxygen evolution electrode during the oxygen evolution process. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the preparation method of the bimetallic phosphate oxygen evolution electrode in one embodiment of the present invention;

[0023] Figure 2 This is a surface morphology diagram of the nickel-iron phosphate electrode of Embodiment 1 of the present invention;

[0024] Figure 3 This is a comparison image of the nickel-iron phosphate electrode of Example 1 of the present invention and the blank substrate LSV;

[0025] Figure 4This is a voltage diagram for the stability test of the nickel-iron phosphate electrode in Example 1 of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0027] like Figure 1 As shown, a method for preparing a bimetallic phosphate oxygen evolution electrode in one embodiment of the present invention includes steps S1-S4.

[0028] Step S1: Clean the nickel substrate in an alkaline solution and rinse with pure water.

[0029] Specifically, in step S1, the nickel substrate refers to a pure nickel material used as the electrode substrate. The nickel substrate is ultrasonically cleaned in an alkaline solution for 10 to 30 minutes to remove oil stains from its surface, and then rinsed with pure water.

[0030] Preferably, the alkaline solution is selected from soapy water, 30% KOH, and metal cleaning solution. The alkaline solution can effectively remove oil stains from the surface of the nickel substrate.

[0031] The nickel substrate is selected from one of nickel mesh, nickel foam, and nickel felt. The aforementioned nickel substrates are resistant to high-temperature alkaline corrosion, have excellent catalytic performance, and exhibit better stability.

[0032] Step S2: Immerse the cleaned nickel substrate in an acidic solution and rinse it with pure water. Place it in pure water for later use.

[0033] Specifically, in step S2, the alkaline-washed nickel substrate is immersed in an acidic solution of 1 to 3 M (mol / L) for 5 to 10 minutes to remove oxides from the surface of the nickel substrate. Then, it is rinsed with pure water and the treated nickel substrate is placed in pure water for later use. The acidic solution can be an HCl solution.

[0034] Step S3: Use a nickel substrate placed in pure water as the cathode, and place two pure nickel materials on both sides of the nickel substrate as two anodes to perform electrodeposition on the nickel substrate in a bimetallic phosphate solution.

[0035] Specifically, in step S3, the treated nickel substrate is used as the cathode, and two pure nickel materials are placed on both sides of the nickel substrate as two anodes, in a bimetallic phosphate solution at a rate of 10 to 30 mA / cm. 2Electrodeposition of nickel substrates was performed at a current density of 20°C to 30°C for 20 to 60 minutes.

[0036] By controlling the current density, temperature, and time, the catalytic layer structure on the nickel substrate surface can be made more stable and have better catalytic performance.

[0037] The bimetallic phosphate solution is prepared by mixing a phosphate solution, at least two metal salt solutions, and a stabilizer.

[0038] Preferably, the phosphate solution is selected from one or more of sodium hypophosphite solution, sodium phosphite solution, or sodium phosphate solution, and the concentration of the phosphate solution is 0.3 to 0.7 M.

[0039] The metal salt solution is selected from two of the following: nickel salt solution, cobalt salt solution, and iron salt solution. Among them, the nickel salt solution is selected from one of nickel sulfate, nickel chloride, or nickel nitrate, and the concentration of the nickel salt solution is 20 to 50 mM (millomoles / L).

[0040] The cobalt salt solution is selected from one of cobalt sulfate, cobalt chloride, or cobalt nitrate, and the concentration of the cobalt salt solution is 10 to 30 mM.

[0041] The iron salt solution is selected from one of ferric sulfate, ferric chloride, or ferric nitrate, and the concentration of the iron salt solution is 10 to 30 mM.

[0042] The combination of phosphate solution and two metal salt solutions forms a bimetallic phosphate solution. The synergistic effect between the bimetallic ions in the bimetallic phosphate can effectively optimize the adsorption energy of the reaction intermediate on the surface of the catalyst layer, thereby significantly improving the intrinsic catalytic activity of the catalyst layer. At the same time, the chemical bond formed between phosphate ions and metal ions is very strong, which enables the bimetallic phosphate to maintain its crystal structure and chemical composition for a long time in high-temperature and high-concentration alkaline electrolytes. It is not easily dissolved or destroyed and has good structural stability and durability.

[0043] The stabilizer is selected from sodium citrate, ethylenediaminetetraacetic acid, and ascorbic acid. Preferably, a 0.1 to 0.5 M sodium citrate solution is used. The stabilizer helps maintain the stability of the solution.

[0044] In one embodiment, two pure nickel materials are placed parallel to each other on both sides of a nickel substrate. This arrangement ensures that during electroplating, the electric field lines are parallel to each other and perpendicular to the cathode (i.e., the nickel substrate), resulting in more uniform electrodeposition.

[0045] Step S4: Rinse the electrode obtained after electrodeposition on the nickel substrate and dry it to obtain a bimetallic phosphate oxygen evolution electrode.

[0046] The present invention will be further described below with reference to specific embodiments.

[0047] Example 1

[0048] Step S1: Select a nickel mesh as the nickel substrate, sonicate the nickel mesh in soapy water for 30 minutes to remove oil, and then clean it with pure water.

[0049] Step S2: Soak the nickel mesh in a 3 M HCl solution for 5 min to remove oxides from the surface of the nickel mesh, then rinse it with pure water and place it in pure water for later use.

[0050] Step S3: At 20 mA / cm 2 At a current density of [value missing], a nickel mesh was used as the cathode, and two pure nickel materials were placed parallel to each other on both sides of the nickel mesh for electrodeposition in a bimetallic phosphate solution. The bimetallic phosphate solution was a mixture of 20 mM nickel chloride solution, 10 mM ferrous sulfate solution, 0.4 M sodium hypophosphite solution, and 0.2 M sodium citrate solution. The electrodeposition time was 60 min, and the temperature was 25 °C.

[0051] Step S4: Rinse the electrode obtained after nickel mesh electrodeposition and dry it to obtain a bimetallic phosphate oxygen evolution electrode (i.e., nickel iron phosphate electrode).

[0052] The bimetallic phosphate oxygen evolution electrode obtained in Example 1 was subjected to structural analysis and EDS analysis.

[0053] like Figure 2 As shown, a spherical catalytic layer structure was formed on the surface of the bimetallic phosphate oxygen evolution electrode. Table 1 below shows that the mass fractions of Ni, Fe, O, and P on the surface of the nickel-iron phosphate electrode are 21.5%, 65.5%, 6.2%, and 5.5%, respectively, indicating that the preparation of the nickel-iron phosphate catalytic layer was successfully achieved.

[0054] Table 1 Elemental content on the surface of nickel-iron phosphate electrode

[0055]

[0056] Using an electrochemical workstation, the nickel-iron phosphate electrode and the blank nickel grid electrode from Example 1 were tested under conditions of 30% KOH and 80°C, and their LSV (linear sweep voltammetry) curves were obtained. Figure 3 As shown, at a current density of 500 mA / cm² 2 Under the given conditions, the overpotential of the nickel-iron phosphate electrode is 226 mV lower than that of the blank substrate, thus the electrochemical reaction of the nickel-iron phosphate electrode is more efficient and consumes less energy.

[0057] A long-term stability test was conducted for 240 h in 30% KOH at 80°C, using a bright nickel mesh as the counter electrode and the nickel-iron phosphate electrode from Example 1 as the anode, under zero-gap conditions. Figure 4As shown, the electrode voltage of nickel-iron phosphate remained stable without any increase, indicating that the electrode has good stability.

[0058] The nickel-iron phosphate electrode was subjected to ultrasonic weight loss test in 30% KOH solution at 60℃. The results are shown in Table 2. The weight loss rate of the nickel-iron phosphate electrode was extremely low, indicating that the catalyst layer of the nickel-iron phosphate electrode prepared by electrodeposition method has a strong bonding force with the substrate and a more stable structure, thus the nickel-iron phosphate electrode has good stability.

[0059] Table 2. Results of ultrasonic weight loss test of nickel-iron phosphate electrode

[0060]

[0061] Another embodiment of the present invention provides a bimetallic phosphate oxygen evolution electrode prepared by the preparation method of any of the above embodiments.

[0062] Another embodiment of the present invention provides an application of the above-mentioned bimetallic phosphate oxygen evolution electrode in the field of alkaline water electrolysis for hydrogen production.

[0063] In summary, the bimetallic phosphate oxygen evolution electrode of this invention utilizes bimetallic phosphate as the active material and employs a one-step electrodeposition method to directly grow the active material on a nickel substrate, forming a strong chemical bond. This avoids the use of binders, ensuring excellent electronic conduction and structural stability. The entire preparation process does not require high temperature and high pressure; the phosphating process is carried out under mild liquid phase conditions. The process is simple, safe, and low-cost, making it suitable for large-scale production. Furthermore, this preparation method optimizes the adsorption free energy of the catalyst layer on the surface of the bimetallic phosphate oxygen evolution electrode for reaction intermediates through the synergistic electronic effect of the two metals, thereby enhancing the intrinsic activity of the oxygen evolution reaction. Simultaneously, it forms a relatively stable catalyst structure, improving the stability of the bimetallic phosphate oxygen evolution electrode during the oxygen evolution process.

[0064] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a bimetallic phosphate oxygen evolution electrode, characterized in that, include: The nickel substrate was cleaned in an alkaline solution to remove oil and then rinsed with pure water. The cleaned nickel substrate is immersed in an acidic solution and rinsed with pure water, then placed in pure water for later use. The nickel substrate placed in pure water is used as the cathode, and two pure nickel materials are placed on both sides of the nickel substrate as two anodes. Electrodeposition is performed on the nickel substrate in a bimetallic phosphate solution. The electrode obtained after electrodeposition on the nickel substrate is rinsed clean and dried to obtain a bimetallic phosphate electrode.

2. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 1, characterized in that, The bimetallic phosphate solution comprises a phosphate solution, at least two metal salt solutions, and a stabilizer.

3. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 2, characterized in that, The phosphate solution is selected from one or more of sodium hypophosphite solution, sodium phosphite solution, or sodium phosphate solution; and / or, the concentration of the phosphate solution is 0.3 to 0.7 M.

4. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 2, characterized in that, The metal salt solution is selected from two of nickel salt solution, cobalt salt solution and iron salt solution; and / or, the stabilizer is selected from one or more of sodium citrate, ethylenediaminetetraacetic acid and ascorbic acid.

5. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 4, characterized in that, The nickel salt solution is selected from nickel sulfate, nickel chloride, or nickel nitrate; and / or the concentration of the nickel salt solution is 20 to 50 mM.

6. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 4, characterized in that, The cobalt salt solution is selected from cobalt sulfate, cobalt chloride, or cobalt nitrate; and / or, the concentration of the cobalt salt solution is 10 to 30 mM.

7. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 4, characterized in that, The iron salt solution is selected from one of ferric sulfate, ferric chloride, or ferric nitrate; and / or the concentration of the iron salt solution is 10 to 30 mM.

8. The method for preparing the bimetallic phosphate oxygen evolution electrode according to claim 1, characterized in that, The current density of the electrodeposition is 10 to 30 mA / cm². 2 The time is 20 to 60 minutes, and the temperature is 20°C to 30°C.

9. A bimetallic phosphate oxygen evolution electrode prepared by the preparation method according to any one of claims 1-8.

10. The application of the bimetallic phosphate oxygen evolution electrode as described in claim 9 in the field of alkaline water electrolysis for hydrogen production.

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