Sandwich-structure foam electrode for anion exchange membrane electrolyzed water as well as preparation method and application of sandwich-structure foam electrode

Abstract

The invention relates to a sandwich structure foam electrode for anion exchange membrane electrolyzed water and a preparation method thereof. The foam electrode with the sandwich structure has a sandwich type sandwich structure, is represented by a general formula M1M2M1-NC, and is specifically a three-layer foam metal combination body (M1M2M1) which is formed by clamping a foam metal M2 between two foam metals M1 and the surface of which is modified by a nitrogen-doped carbon (NC) material. Compared with the prior art, in the prepared M1M2M1-NC foam electrode with the sandwich structure, the foam metal serves as a structure substrate and a catalytic active site at the same time; the NC coating layer epitaxially grown on the surface can effectively relieve the problem of demetallization dissolution of a catalyst material while optimizing an electron transmission channel, and is beneficial to prolonging the service life of a catalytic electrode; in addition, the catalyst also has the advantages of high catalytic activity, good stability, simple and convenient preparation method, capability of effectively reducing the industrial application cost and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water electrolysis hydrogen electrode, in particular to a sandwich structure foam electrode for anion exchange membrane water electrolysis and a preparation method and application thereof. BACKGROUND

[0002] As a new type of water electrolysis hydrogen production technology, anion exchange membrane electrolyzer (AEMWE) has become an important way to realize green hydrogen production due to its technical advantages of both alkaline electrolyzer (AWE) and proton exchange membrane electrolyzer (PEMWE). The use of this technology not only can significantly reduce the energy consumption of hydrogen production process, but also can realize the output of high-purity hydrogen. Specifically, its technical advantages mainly lie in three aspects: 1) benefiting from the use of non-noble metal catalyst, AEMWE has similar low-cost characteristics as AWE; 2) by introducing anion exchange membrane, AEMWE can achieve more than 80% of electrolysis efficiency at high current density; 3) modular design makes AEMWE have similar adaptability as PEMWE, and its hydrogen production rate can be flexibly adapted to the fluctuating input of renewable energy such as wind power and photovoltaic.

[0003] However, the industrialization process of AEMWE is still subject to key technical bottlenecks such as electrode and electrocatalyst. In the anode side oxygen evolution reaction (OER) process, due to the need for high activation energy for the adsorption of oxygen intermediates, the commonly used traditional Ni-based catalyst requires a high overpotential to drive the effective reaction, thus directly leading to the reduction of overall efficiency; although the hydrogen evolution reaction (HER) on the cathode side has good thermodynamic properties, the commonly used Pt-based catalyst costs up to 40% of the total system cost, while the relatively low-cost Ni-based catalyst is prone to structural changes in long-term operation, accompanied by the electrochemical dissolution of some elements, resulting in the loss of effective active sites, performance degradation and reduction of working life. In addition, the traditional electrode preparation method is to coat or attach the powder catalyst to the surface of the current collector, which is subject to the technical limitations of insufficient bonding force between the two, and the catalyst in such electrodes is prone to fall off at high working voltage, thus seriously shortening the service life of the electrolyzer.

[0004] In recent years, a large number of researches on electrocatalytic materials have been reported in the field of AEMWE, and important breakthroughs have been made. For example: noble metal oxides, 3d transition metal (Fe, Co and Ni) oxides, layered double hydroxides (LDHs), sulfides, phosphides, etc. Among them, NiFe-based and NiCo-based materials are considered to be the most promising non-noble metal electrocatalysts due to their unique structure and rich active sites. However, the synthesis process of such materials is complex, and there is a phenomenon of demetallization dissolution in alkaline environment, which limits their long-term stable application at industrial scale.

[0005] To solve the problems of the catalytic electrode in the AEMWE, at the material design level, a metal composite electrode with a self-supporting structure needs to be developed, while the strong electron capture ability of heteroatoms is used to optimize the adsorption of reaction intermediates. At the synthesis process level, simple and convenient green preparation technology needs to be developed. At the engineering application level, a three-dimensional interface system with porous structure can be constructed to improve the stability of the catalyst materials in the electrode through the synergistic effect of mechanical bonding and chemical bonding, so as to promote the commercialization application process of AEMWE technology.

[0006] Patent application CN109023412A discloses a preparation method of a nanoporous nickel-copper / amorphous composite electrode for preparing electrode materials for hydrogen production by water electrolysis. The technical route includes two core steps: (1) using melt quenching method to prepare Ni-Cu-based amorphous alloy as precursor; (2) using chemical dealloying method to selectively corrode active metal components in the precursor, finally obtaining a "sandwich" composite structure with nanoporous Ni-Cu structure on the surface and amorphous state inside. However, the existing melt quenching technology is difficult to realize continuous and mass production, and the corrosion rate of chemical dealloying is affected by many factors such as solution concentration, temperature, and uniformity of precursor composition, which increases the risk of excessive corrosion of the electrode, thereby affecting the integrity of the electrode structure and working performance.

[0007] Patent application CN119082761A discloses a preparation method of a high-current-density hydrogen evolution electrode for alkaline water electrolysis. It uses a metal mesh as the cathode by electroplating method, and grows nano Co3O4 catalyst in-situ on the metal Co interlayer, so that the prepared electrode shows a sandwich structure. However, the difference in thermal expansion coefficient between the metal Co interlayer and the Co3O4 catalyst layer easily leads to interfacial shear stress, accelerates the generation of cracks on the electrode surface, increases the charge transfer resistance, and thus reduces the catalytic performance. Secondly, the direct contact of Co3O4 with the electrolyte increases the risk of chemical dissolution or phase change of Co3O4 under strong alkaline and high potential conditions, resulting in a decrease in catalytic activity. Moreover, the preparation process involves multiple processes such as nano material synthesis and in-situ growth, which requires strict control of parameters such as temperature, time, and reactant concentration, and is difficult to control. The complex preparation process further increases the production cost, which is not conducive to large-scale industrialization and application.

[0008] Patent application CN119040932A discloses a method for preparing a catalytic electrode for anion exchange membrane electrolyzers, along with its products and applications. This invention uses nickel foam as a substrate material and grows nickel, cobalt, and iron non-precious metal catalysts on it through electrodeposition and hydrothermal synthesis, forming a self-supporting anode catalytic electrode with a multi-level nanocone-nanose needle structure. This avoids the use of ionomers, simplifies the process, and improves the catalyst's durability and active area. However, this invention employs a complex two-step chemical reaction, increasing the subsequent wastewater treatment steps / costs and the risk of environmental pollution. Furthermore, the direct exposure of the catalyst to the solution can accelerate its performance degradation.

[0009] Patent application CN111604078A discloses a NiCoP / CoP / CoSe@NC catalyst and its preparation method. This invention uses nitrogen-doped nanofibers supported on nickel foam to prepare the catalyst. The nitrogen-doped nanofibers consist of a core and a shell. The core includes heterostructures formed by NiCoP and CoP, and CoSe and CoP. The shell is amorphous nitrogen-doped carbon coating the heterostructure. "NC" is short for nitrogen-doped carbon, which not only protects the internal crystal structure but also, due to the difference in work function between itself and the internal heterostructure, generates a unique Mott-Schottky effect, forming a Schottky structure that promotes electron transfer from the interior to the exterior, thus synergistically enhancing catalytic activity. However, the catalyst provided by this invention has low mechanical strength and is prone to structural deformation and damage during electrolysis due to bubble generation or mechanical vibration, leading to a decrease in catalytic performance.

[0010] Therefore, developing catalytic electrodes with high mechanical strength, good corrosion resistance, and fast electron transport is of great significance for promoting the large-scale industrial application of AEMWE. Summary of the Invention

[0011] The purpose of this invention is to address the shortcomings of existing technologies by providing a sandwich-structured foam electrode for anion exchange membrane electrolysis of water, its preparation method, and its application. This invention improves the mechanical strength of the electrode, alleviates the demetallization problem of the catalyst in the electrode, and increases the electron transport rate on the electrode surface, thereby enhancing electrocatalytic activity and stability.

[0012] The objective of this invention can be achieved through the following technical solutions: A sandwich-structured foam electrode for anion exchange membrane electrolysis of water, wherein the sandwich-structured foam electrode has a sandwich-like interlayer structure, which is generally represented by the formula M1M2M1-NC. The interlayer structure is a three-layer foam metal composite M1M2M1 with nitrogen-doped carbon material NC on its surface.

[0013] Furthermore, the three-layer foam metal composite M1M2M1 is composed of two foam metal pieces M1 sandwiching one foam metal piece M2. Furthermore, the foam metals M1 and M2 are one of Fe, Co, Ni, Cu, Ti, and Al, and M1 and M2 are different metals.

[0014] This invention also provides a method for preparing a sandwich-structured foam electrode for anion exchange membrane water electrolysis, comprising the following steps: (1) The foam metal M2 is sandwiched between two pieces of foam metal M1, and then multi-directional compression is performed to make them tightly bonded, forming a three-layer foam metal composite M1M2M1. The compression pressure is 0.5~1.0 MPa, the compression time is 2~10 s, and the thickness of the metal foam is 0.5~2.0 mm.

[0015] (2) The three-layer foam metal composite M1M2M1 obtained in step (1) is used as the working electrode, the platinum wire as the counter electrode, and the saturated calomel electrode as the reference electrode. Constant potential deposition is carried out in KOH solution containing amine compounds and sulfates. Then the working electrode is removed from the electrolyte and dried. (3) The dried three-layer foam metal composite electrode M1M2M1 obtained in step (2) is subjected to high-temperature heat treatment in a nitrogen atmosphere to obtain a nitrogen-doped carbon-modified sandwich structure foam electrode M1M2M1-NC. Further, the amine compound includes one or more of aniline, ethylenediamine, propylamine, isopropylamine, and dopamine.

[0016] Furthermore, the sulfate includes one or more of Na2SO4, MgSO4, K2SO4, CuSO4, ZnSO4, and Fe2(SO4)3.

[0017] Furthermore, in the KOH solution containing amine compounds and sulfates, the solubility of the amine compounds is 0.01~1 M; the concentration of the sulfates is 0.01~1 M; and the concentration of the KOH solution is 0.1~6 M.

[0018] Furthermore, the constant potential deposition potential is 0.8~1.2 V relative to the SCE electrode; the deposition time is 1~20 min.

[0019] Furthermore, the drying is carried out in air for 12-24 hours.

[0020] Furthermore, the high-temperature heat treatment is performed at a temperature of 200~600 ℃ for a time of 2~4 h.

[0021] The present invention also provides an application of a sandwich-structured foam electrode for anion exchange membrane electrolysis of water, wherein the sandwich-structured foam electrode is used as the cathode or anode of anion exchange membrane electrolyzer.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The sandwich-structured foam electrode M1M2M1-NC prepared by this invention has a three-layer sandwich structure that is physically pressed and fixed to form a rigid support frame. Compared with traditional electrodes, it can effectively resist structural deformation and damage caused by bubble generation or mechanical vibration during electrolysis. The three-layer foam-metal composite M1M2M1 forms a continuous metal conductive network, which significantly improves the electron transport rate compared with traditional particle-attached electrodes, making it suitable for water electrolysis processes under high current density. The porous nature of the sandwich structure can increase the contact area between the electrolyte and the catalyst, promote bubble escape, and improve the efficiency of electrocatalytic reaction.

[0023] 2. The sandwich-structured foam electrode M1M2M1-NC prepared by this invention has a nitrogen-doped carbon (NC) coating layer formed during high-temperature heat treatment that combines with the metal surface. This layer acts as a physical barrier, inhibiting the dissolution (demetallization) of the metal under alkaline conditions, enhancing corrosion resistance, and extending service life. Nitrogen doping can adjust the electronic structure of the carbon layer, forming an electron-rich region and reducing the overpotential of the electrocatalytic reaction. The high conductivity of the NC coating layer can accelerate surface electron transfer and reduce charge transfer resistance. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the electrode obtained in Example 1 of the present invention; Figure 2 This is a comparison diagram of the OER activity of the electrodes obtained in Example 1 and Comparative Example 1 of the present invention; Figure 3 This is a comparison chart of the long-term OER stability of the electrodes obtained in Example 1 and Comparative Example 1 of the present invention. Figure 4 This is a comparison diagram of the HER activity of the electrodes obtained in Example 2 and Comparative Example 2 of the present invention; Figure 5 This is a comparison chart of the long-term HER stability of the electrodes obtained in Example 2 and Comparative Example 2 of the present invention; Figure 6 The diagram shows the working performance of anion exchange membrane electrolyzers assembled using the electrodes obtained in Examples 1 and 2 of this invention as anodes and cathodes, respectively, at 25°C.

[0025] Figure 7 The diagram shows the working performance of anion exchange membrane electrolyzers assembled using the electrodes obtained in Examples 1 and 2 of this invention as anode and cathode, respectively, at 50°C.

[0026] Figure 8 The figures show the long-term working stability curves of anion exchange membrane electrolyzers assembled using the electrodes obtained in Examples 1 and 2 of this invention as anodes and cathodes, respectively, under different conditions. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0028] The purpose of this invention is to improve the mechanical strength of the electrode, alleviate the demetallization problem of the catalyst in the electrode, and increase the electron transport rate on the electrode surface, thereby improving the electrocatalytic activity and stability.

[0029] The raw materials used in this invention are all commercially available, such as the raw materials selected in the following embodiments: Ni foam, purchased from Hebei Aegis Metal Materials Co., Ltd., 1 mm thick, 80 ppi pore size; Fe foam, purchased from Suzhou Keshenghe Metal Materials Co., Ltd., 1 mm thick, 95 ppi pore size; Foam Co, purchased from Suzhou Chint Rong New Material Co., Ltd., 0.5 mm thick, 80 ppi pore size.

[0030] The objective of this invention can be achieved through the following technical solutions: A method for preparing a sandwich-structured foam electrode for anion exchange membrane water electrolysis includes the following steps: (1) Sandwich foam metal M2 between two pieces of foam metal M1, and then press them together from different angles such as the middle and the edge to form a three-layer foam metal composite M1M2M1; metals M1 and M2 are one of Fe, Co, Ni, Cu, Ti and Al respectively, with a thickness of 0.5~2.0 mm; the pressing pressure is 0.5~1.0 MPa, and the pressing time is 2~10s. (2) Using the three-layer foam metal composite M1M2M1 obtained in step (1) as the working electrode, platinum wire as the counter electrode, and saturated calomel electrode as the reference electrode, constant potential deposition is performed in a KOH solution containing amine compounds and sulfates. The working electrode is then removed from the electrolyte and dried. The amine compounds are one or more of aniline, ethylenediamine, propylamine, isopropylamine, and dopamine; the sulfates are one or more of Na2SO4, MgSO4, K2SO4, CuSO4, ZnSO4, and Fe2(SO4)3; the solubility of the amine compounds is 0.01~1 M, the concentration of the sulfates is 0.01~1 M, and the concentration of the KOH solution is 0.1~6 M; the constant potential deposition potential is 0.8~1.2 V (vs. SCE); and the deposition time is 1~20 minutes. min; (3) The dried three-layer foam metal composite M1M2M1 electrode obtained in step (2) is subjected to high-temperature heat treatment in a nitrogen atmosphere at a temperature of 200~600℃ for 2~4 h to obtain a nitrogen-doped carbon-modified sandwich structure foam electrode M1M2M1-NC.

[0031] To further understand the present invention, the following embodiments are provided. It is worth noting that, unless otherwise specified, all raw materials used in the present invention are commercially available; and all methods and equipment employed are common in the art.

[0032] Example 1 The sandwich-structured foam electrode NiFeNi-NC-10-350-2 was prepared by the following method: (1) A 0.4 cm × 0.6 cm foam metal Fe, which has been cleaned with hydrochloric acid solution, is sandwiched between two 0.5 cm × 1 cm foam metal Ni pieces, and then pressed together with a pressure of 0.5 MPa for 10 s to obtain a three-layer foam metal composite NiFeNi. (2) The three-layer foam metal composite NiFeNi obtained in step (1) is used as the working electrode, the platinum wire as the counter electrode, the saturated calomel electrode (SCE) as the reference electrode, and 100 mL of 1M KOH solution containing 0.01 M aniline and 0.01 M Na2SO4 as the electrolyte. The constant potential deposition is carried out at a potential of 0.8 V (vs. SCE) for 10 min. Then the three-layer foam metal composite NiFeNi is taken out from the electrolyte and dried in the air for 24 h to obtain a sandwich structure foam electrode precursor containing a polyaniline (PANI) coating layer. (3) The sandwich structure foam electrode precursor with PANI coating obtained in step (2) is placed in a tube furnace filled with N2 and heat-treated at 350 °C for 2 h to obtain nitrogen-doped carbon (NC) modified sandwich structure foam electrode NiFeNi-NC-10-350-2 (in the name, 10, 250 and 2 represent electrodeposition time, high temperature and time of high temperature treatment, respectively).

[0033] The resulting foam electrode NiFeNi-NC-10-350-2 is shown in the image. Figure 1 It can be seen that the obtained electrode is a porous structure with tightly bonded foam metal.

[0034] Example 2 The sandwich-structured foam electrode NiCoNi-NC-5-350-2 was prepared by the following method: This embodiment is basically the same as Embodiment 1, except that in this embodiment, in step (1), foam metal Co is sandwiched between two pieces of foam metal Ni and pressed together with a pressure of 1.0 MPa for 2 s to obtain a three-layer foam metal composite NiCoNi; in step (2), the concentration of aniline is 0.5 M, the concentration of Na2SO4 is 0.05 M, the constant potential deposition potential is 1.0 V, the time is 5 min, and the concentration of KOH solution is 2 M; in step (3), the sandwich structure foam electrode precursor is heat-treated at 350 ℃ for 2 h in a tube furnace filled with N2. The obtained sandwich structure foam electrode is marked as NiCoNi-NC-5-350-2.

[0035] Example 3 The sandwich-structured foam electrode NiFeNi-NC-20-600-4 was prepared by the following method: This embodiment is basically the same as Embodiment 1, except that in this embodiment, in step (2), the concentration of aniline is 1 M, the concentration of Na2SO4 is 1 M, the concentration of KOH solution is 6 M, the constant potential deposition potential is 1.2 V (vs. SCE), and the time is 20 min; in step (3), the sandwich structure foam electrode precursor is heat-treated at 600 °C for 4 h in a tube furnace filled with N2. The resulting sandwich structure foam electrode is labeled as NiFeNi-NC-20-600-4.

[0036] Example 4 The sandwich-structured foam electrode NiFeNi-NC-1-200-4 was prepared by the following method: This embodiment is basically the same as Embodiment 1, except that in this embodiment, in step (2), the concentration of aniline is 0.5 M, the concentration of Na2SO4 is 0.5 M, the constant potential deposition potential is 1.2 V, the time is 1 min, the concentration of KOH solution is 0.1 M, and the drying time is 12 h; in step (3), the sandwich structure foam electrode precursor is heat-treated at 200 ℃ for 2 h in a tube furnace filled with N2. The resulting sandwich structure foam electrode is labeled as NiFeNi-NC-1-200-4.

[0037] Example 5 The sandwich-structured foam electrode NiCoNi-NC-10-200-4 was prepared by the following method: This embodiment is basically the same as Embodiment 1, except that in this embodiment, in step (1), foam metal Co is sandwiched between two pieces of foam metal Ni to obtain a three-layer metal foam composite NiCoNi; in step (2), the concentration of aniline is 0.1 M, the concentration of Na2SO4 is 0.1 M, the constant potential deposition potential is 1.2 V (vs. SCE), and the concentration of KOH solution is 0.1 M; in step (3), the sandwich structure foam electrode precursor is heat-treated at 200 °C for 4 h in a tube furnace filled with N2. The obtained sandwich structure foam electrode is labeled as NiCoNi-NC-10-200-4.

[0038] Comparative Example 1 1.5 mmol of nickel chloride hexahydrate (NiCl2·6H2O), 0.5 mmol of ferric chloride hexahydrate (FeCl3·6H2O), and 5 mmol of urea were dissolved in 35 mL of deionized water. After stirring for about 1 h, the solution was sonicated for 20 min. The resulting solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave and kept at 120 °C for 12 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed with deionized water and ethanol, and then dried in a vacuum oven at 50 °C for 12 h to obtain NiFe LDH powder.

[0039] A 0.8 × 0.5 cm nickel foam was immersed in a mixed solution containing 5 mg NiFe LDH powder, 650 µL ethanol, 300 µL deionized water and 50 µL 5 wt.% Nafion. After soaking overnight, it was rinsed with deionized water and air-dried at room temperature to obtain the NiFe LDH-NF electrode.

[0040] Comparative Example 2 1 mmol of nickel chloride hexahydrate (NiCl2·6H2O), 2 mmol of cobalt chloride hexahydrate, and 5 mmol of hexamethylenetetramine (HMTA) were dissolved in 35 mL of deionized water. After stirring for about 1 h, the solution was sonicated for 20 min. The resulting solution was then transferred to a 50 mL Teflon-lined stainless steel autoclave and kept at 95 °C for 8 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed with deionized water and ethanol, and then dried in a vacuum oven at 50 °C for 12 h to obtain NiCo LDH powder.

[0041] A 0.8 × 0.5 cm nickel foam was immersed in a mixed solution containing 5 mg NiCo LDH powder, 650 µL ethanol, 300 µL deionized water and 50 µL 5 wt.% Nafion. After soaking overnight, it was rinsed with deionized water and air-dried at room temperature to obtain a NiCo LDH-NF electrode.

[0042] The performance of the electrodes obtained in each embodiment and comparative example was tested: (1) HER and OER tests: Using the obtained sandwich-structured foam electrode M1M2M1-NC as the working electrode, platinum wire as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode, HER and OER tests were performed in 1M KOH solution at room temperature. The potential range for HER was -0.7 to 0 V (vs. RHE), and the scan rate was 5 mV / s; the potential range for OER was 1.2 to 1.8 V (vs. RHE), and the scan rate was 5 mV / s.

[0043] (2) Water electrolysis test: An anion exchange membrane electrolyzer was assembled using the obtained sandwich structure foam electrode M1M2M1-NC as the cathode or anode, and water electrolysis tests were conducted in 1 M and 6 M KOH solutions, respectively. The test voltage range was 1.2~2.0 V, and the scan rate was 5 mV / s. Stability tests were conducted at voltages of 1.75 V and 1.90 V.

[0044] like Figure 2 As shown, this is a comparison chart of the OER activity of the electrodes obtained in Example 1 and Comparative Example 1. Figure 2 It can be seen that, in 1M KOH solution, the OER catalytic activity of the sandwich structure foam electrode NiFeNi-NC-10-350-2 obtained in Example 1 is significantly higher than that of the NiFe LDH-NF electrode prepared in Comparative Example 1. Figure 3 This is a comparison chart of the long-term OER stability of the electrodes obtained in Example 1 and Comparative Example 1. Figure 3 It can be seen that the OER long-term working stability of the sandwich structure foam electrode NiFeNi-NC-10-350-2 obtained in Example 1 is significantly better than that of the NiFe LDH-NF electrode prepared in Comparative Example 1. Its current density hardly decays after working at 1.5 V (vs. RHE) for 50 h, while the current density of the NiFe LDH-NF electrode drops by more than one-third after only 30 h.

[0045] like Figure 4 As shown, this is a comparison chart of the HER activity of the electrodes obtained in Example 2 and Comparative Example 2. Figure 4 It can be seen that, in 1M KOH solution, the HER catalytic activity of the sandwich structure foam electrode NiCoNi-NC-5-350-2 obtained in Example 2 is significantly higher than that of the NiCo LDH-NF electrode prepared in Comparative Example 2. Figure 5 This is a comparison chart of the long-term HER stability of the electrodes obtained in Example 2 and Comparative Example 2. Figure 5 It can be seen that the long-term HER stability of the sandwich structure foam electrode NiCoNi-NC-5-350-2 obtained in Example 2 is significantly better than that of the NiCo LDH-NF electrode prepared in Comparative Example 2. The current density of the NiCo LDH-NF electrode shows almost no decay after 50 hours of operation at -0.25 V (vs. RHE), while the current density of the NiCo LDH-NF electrode shows a significant decrease after only 20 hours.

[0046] The sandwich-structured foam electrode NiFeNi-NC-10-350-2 obtained in Example 1 and the sandwich-structured foam electrode NiCoNi-NC-5-350-2 obtained in Example 2 were used as the anode and cathode, respectively, to assemble an anion exchange membrane electrolyzer (NiCoNi-NC-5-350-2||NiFeNi-NC-10-350-2), and water electrolysis tests were conducted. The results are as follows: Figures 6-8 As shown in Table 1, the anion exchange membrane electrolyzer exhibits excellent performance in both 1 M and 6 M KOH solutions at both room temperature (25°C) and 50°C. In particular, it achieves a 10 mA cm⁻¹ solution with only a 39 mV overpotential in 1 M KOH at 50°C. -2 The current density was achieved at 1000 mA cm⁻¹ in 6 M KOH at 50 °C. -2 The operating voltage for current density is only 1.891 V.

[0047] Table 1. Specific performance data of the anion exchange membrane electrolyzer.

[0048] Combination Figures 2-8 As can be seen from the performance data in Table 1, the excellent OER and HER performance of the catalysts prepared in Examples 1 and 2, and the good water electrolysis performance and long-term working stability of the anion exchange membrane electrolyzer assembled by combining the two, are due to the good mechanical strength, corrosion resistance and fast electron transport capability of the electrode constructed in this invention.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A sandwich structure foam electrode for electrolysis of water using an anion exchange membrane, characterized by, The sandwich structure foam electrode has a sandwiched interlayer structure, which is represented by a general formula M1M2M1-NC, and is a three-layer foam metal combination M1M2M1 with a surface modified with a nitrogen-doped carbon material NC.

2. The sandwich structure foam electrode for electrolysis of water using anion exchange membrane according to claim 1, characterized in that, The three-layer foam metal combination M1M2M1 is composed of two pieces of foam metal M1 sandwiching one piece of foam metal M2. The foam metal M1 and the foam metal M2 are each one of Fe, Co, Ni, Cu, Ti, and Al, and M1 and M2 are different metals.

3. A method for preparing a sandwich-structured foam electrode for electrolysis of water using an anion exchange membrane as claimed in any one of claims 1 to 2, characterized by, The method comprises the following steps: (1) sandwiching the foam metal M2 between two pieces of foam metal M1, and then performing multi-directional pressing to tightly combine the foam metals to form a three-layer foam metal combination M1M2M1; (2) taking the three-layer foam metal combination M1M2M1 obtained in step (1) as a working electrode, a platinum wire as a counter electrode, and a saturated calomel electrode (SCE) as a reference electrode, and performing constant potential deposition in a KOH solution containing an amine compound and a sulfate salt, and then taking the working electrode out of the electrolyte and drying; (3) performing high-temperature heat treatment on the dried three-layer foam metal combination M1M2M1 electrode obtained in step (2) in a nitrogen atmosphere to obtain a nitrogen-doped carbon modified sandwich structure foam electrode M1M2M1-NC.

4. The method of claim 3, wherein the method is characterized by: The amine compound in step (2) includes one or more of aniline, ethylenediamine, propylamine, isopropylamine, and dopamine.

5. The method of claim 3, wherein the method is characterized by: The sulfate salt in step (2) includes one or more of Na2SO4, MgSO4, K2SO4, CuSO4, ZnSO4, and Fe2(SO4)3.

6. The method of claim 3, wherein the method is characterized by: In step (2), the solubility of the amine compound in the KOH solution containing the amine compound and the sulfate salt is 0.01-1 M, the concentration of the sulfate salt is 0.01-1 M, and the concentration of the KOH solution is 0.1-6 M.

7. The method of claim 3, wherein the method is characterized by: The potential for the constant potential deposition in step (2) is 0.8-1.2 V relative to the SCE electrode. The deposition time is 1-20 min.

8. The method of claim 3, wherein the method is characterized by: The drying in step (2) is performed in air, and the drying time is 12-24 h.

9. The method of claim 3, wherein the method is characterized by: The temperature for the high-temperature heat treatment in step (3) is 200-600 ℃, and the time is 2-4 h.

10. Use of a sandwich structure foam electrode for electrolysis of water according to any one of claims 1 to 9, characterized in that, The sandwich structure foam electrode is used as a cathode or an anode of an anion exchange membrane electrolyzer.

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