Nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnection grid film and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalytic materials, and particularly relates to a nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnection grid film and a preparation method and application thereof. The preparation method comprises the following steps: taking an aluminum sheet containing copper impurities as a substrate, and preparing a three-dimensional ordered porous aluminum oxide template through anodic oxidation; then, the nickel-iron-cobalt entropy alloy nanowire is prepared in a pore channel limited range through direct current co-electrodeposition; the nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnection grid film is obtained after the aluminum substrate and the 3D-AAO template are removed, the material is based on the mixed entropy effect and structural integrated design and can be directly used as a self-supporting electrode for efficiently and stably electrolyzing water for oxygen evolution, the three-dimensional grid structure and the self-supporting characteristic of the material promote electrolyte transmission and gas product desorption, and the oxygen evolution efficiency is improved. The mass transfer efficiency is improved, the use of a traditional binder is avoided, and the electrode stability is enhanced; the problems that an existing medium-entropy alloy catalyst is high in synthesis energy consumption, the catalytic activity is poor under the industrial-grade large-current working condition, active substances fall off in the reaction and the like are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic materials, and particularly relates to a nickel-iron-cobalt mesoporous alloy nanowire three-dimensional interconnected mesh film, a preparation method and application thereof. BACKGROUND

[0002] Electrocatalytic water splitting is an important way to produce hydrogen, which can convert green electricity generated by renewable energy such as photovoltaic and wind power into hydrogen energy in the form of storage. In recent years, anion exchange membrane water electrolysis (AEMWE) technology has attracted much attention due to its combination of the low-cost potential of alkaline water electrolysis (AWE) and the high efficiency characteristics of proton exchange membrane water electrolysis (PEMWE). The electrocatalytic water splitting reaction includes the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Among them, OER as the kinetic bottleneck of water splitting, its slow four-electron transfer process in alkaline medium leads to high overpotential, which is a key obstacle to improve energy conversion efficiency.

[0003] Transition metal (Ni, Fe, Co, etc.) based catalysts show potential to replace noble metal OER catalysts due to their advantages of abundant reserves and low cost, but they have inherent limitations such as low intrinsic activity, insufficient stability and difficulty in meeting the application requirements under industrial current density. More importantly, the synthesis of these high-performance non-noble metal catalysts usually involves complex and expensive harsh processes such as high-temperature and high-energy treatment, long-time organic solvent reaction, which seriously restricts the large-scale production and practical application of non-noble metal-based catalysts. Therefore, developing transition metal OER catalysts with high activity, excellent stability, simple synthesis process and low cost is the key to promoting the commercialization process of AEMWE technology.

[0004] In addition, due to the synthesis method of transition metal-based catalysts in the prior art, the obtained product is mostly nanoparticle powder, which needs to be mixed with a binder and coated on a conductive substrate to construct a membrane electrode. However, this powder coating method for preparing a membrane electrode has problems such as easy agglomeration of catalyst particles, large contact resistance, low mass transfer efficiency, and easy falling off of catalyst from the electrode surface when working at high current density. Therefore, how to break through the limitations of the traditional preparation method of transition metal-based catalysts with high energy consumption synthesis path, while maintaining the controllability of components, still faces great challenges in constructing a three-dimensional ordered structure integrated membrane electrode assembly (MEA) electrode material. SUMMARY

[0005] One of the purposes of the present application is to provide a preparation method of a transition metal nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film, which can precisely control the nanowire diameter and length by growing NiFeCo medium entropy alloy nanowires in the confined environment of the template channel, and form a three-dimensional interconnected mesh structure. This three-dimensional ordered medium entropy alloy nanowire grown by template method can not only significantly improve the mass transfer efficiency by promoting the efficient transport of electrolyte and the rapid desorption of electrolytic water product gas, but also avoid the need for adhesives in traditional electrodes due to its unique "structure integration" design.

[0006] To achieve the above purpose, the present application adopts the following technical scheme: a preparation method of a nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film, comprising the following steps: S1, cutting a commercial Al sheet containing impurity Cu and then performing anodic oxidation to grow a 3D porous AAO layer on the Al sheet, and gradually reducing the anodic oxidation voltage by using a continuous pressure reduction method when the growth is about to end, to obtain a 3D-AAO / Al substrate; S2, soaking the 3D-AAO / Al substrate in a phosphoric acid solution to obtain an expanded 3D-AAO / Al substrate; S3, performing electrodeposition on the expanded 3D-AAO / Al substrate in an electrodeposition solution containing nickel salt, iron salt and cobalt salt, the deposited alloy nanowire having a near-equiatomic ratio of the three metals, removing the Al substrate and the 3D expanded AAO layer, and obtaining a nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film, denoted as 3D NiFeCo MEA NW thin film.

[0007] Further improvement on the preparation method of a nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film: Preferably, in step S1, the thickness of the commercial Al sheet containing impurity Cu is 0.1-0.2 mm, and the size after cutting is (5-10) cm 2 .

[0008] Preferably, in step S1, a 0.2-0.5 M H3PO4 mixed solution is used as the electrolyte during anodic oxidation, the solvent of the electrolyte is composed of ethanol and deionized water in a volume ratio of 1:9, and the anodic oxidation parameters are set as follows: oxidation voltage is 190-195 V, temperature is 0-5℃, and oxidation time is 10-20 h.

[0009] Preferably, in step S1, the anodic oxidation voltage is gradually reduced by using a continuous pressure reduction method, the anodic oxidation voltage is reduced by 2-5 V each time, and the anodic oxidation is stopped when the current density is reduced to 0-3 mA cm -2 and the voltage is reduced to 50-55 V.

[0010] Preferably, in step S2, the 3D-AAO / Al substrate is washed with deionized water and then immersed in a phosphoric acid solution with a temperature of 40-50° C. and a concentration of 3-10 wt % for 40-60 min.

[0011] Preferably, in step S3, a two-electrode electrolytic cell is used for electrodeposition, the expanded 3D-AAO / Al substrate is used as the cathode, the Al substrate is used as the current collector, the high-purity Ni sheet is used as the anode, and the solution containing nickel salt, iron salt and cobalt salt is used as the electrodeposition solution. -2 The deposition was carried out at a current density of 1~3 h.

[0012] Preferably, the electrodeposition solution uses deionized water as a solvent, contains 0.12 M NiSO4, 0.12 M NiCl2, 0.04 M FeSO4, 0.04 M CoSO4, 0.5 M H3BO3 and 0.05 mg / mL~0.2 mg / mL ascorbic acid, and the pH is adjusted to 2.0~3.0.

[0013] Preferably, in step S3, the electrodeposited product is placed in a 1-5 M NaOH solution, and the Al substrate and the 3D pore-enlarged AAO layer are removed by chemical etching.

[0014] The second object of the present invention is to provide a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires prepared by the preparation method of any one of the above-mentioned three-dimensional interconnected grid films of nickel-iron-cobalt medium-entropy alloy nanowires.

[0015] The third object of the present invention is to provide an application of the above-mentioned nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected grid membrane as a self-supporting integrated alkaline OER reaction electrode in industrial water electrolysis to produce hydrogen.

[0016] The beneficial effects of the present invention compared to the prior art are: (1) The present invention relates to a method for constructing a three-dimensional interconnected grid structure film of nickel-iron-cobalt medium-entropy alloy nanowires (referred to as 3DNiFeCo MEA NW). The invention first uses an aluminum sheet containing a certain amount of copper impurities for anodization, and grows a layer of three-dimensional ordered porous anodic aluminum oxide (3D-AAO) with vertical and horizontal channels interconnected on the Al sheet. A dense, non-porous barrier layer is naturally formed at the bottom of the three-dimensional porous AAO layer near the aluminum substrate. During the anodization process, the thickness of the barrier layer is proportional to the applied voltage (usually about 1 nm / V). The barrier layer formed at a constant high voltage (190 V) is very thick (about 190 nm). When the anodization is about to end, the voltage is gradually reduced to 50 V by a continuous voltage reduction method, so that the barrier layer undergoes mild and controllable electrochemical dissolution / reconstruction, and the thickness is reduced to about 50 nm, thereby obtaining a 3D-AAO / Al substrate with a thinned barrier layer. The 3D-AAO / Al substrate was immersed in a 3-10 wt% phosphoric acid solution at 40-50°C. The barrier layer was then gently thinned (to ensure its permeability) and the AAO pores were slightly enlarged to create an expanded 3D-AAO / Al substrate, creating conditions for subsequent electrodeposition of nanomaterials. By precisely controlling the concentration ratio of the nickel-iron-cobalt ternary metal electrolyte, a nickel-iron-cobalt medium-entropy alloy nanowire (NiFeCo) with mixed entropy properties was constructed by direct current co-electrodeposition within the confined pores. The aluminum substrate and AAO template were then selectively etched away, followed by washing with deionized water and drying, ultimately yielding a three-dimensional interconnected mesh membrane of NiFeCo medium-entropy alloy nanowires. In the initial stage of the OER reaction, the surface of the NiFeCo medium-entropy alloy is reconstructed to generate an ultra-thin Ni(FeCo)OOH coating layer, forming an ordered heterojunction core-shell structure. This structure plays a dual role in the alkaline environment: on the one hand, it forms a passivation protective layer to effectively prevent the nanowires from being corroded under harsh alkaline and oxidizing conditions, significantly improving the mechanical and electrochemical stability of the structure; on the other hand, it provides abundant active sites to enhance the intrinsic electrochemical activity.

[0017] (2) Medium-entropy alloy (MEA) is a key concept different from traditional alloys, which refers to a special solid solution formed by 2-4 main elements with near-equiatomic ratio, with an entropy stabilization effect. The mixing entropy of medium-entropy alloy (MEA) is between 1R and 1.5R, which not only maximizes the advantages of high-entropy alloys, but also provides clearer catalytic active sites and more precise composition control. However, the significant difference in reduction potential of nickel, iron and cobalt metal ions makes it extremely challenging to achieve uniform co-deposition of medium-entropy alloy through conventional electrodeposition. The present application overcomes this difficulty by precisely regulating the concentration ratio of nickel-iron-cobalt ternary metal electrolyte and utilizing the spatial confinement effect of three-dimensional AAO template channels, and precisely constructs a three-dimensional interconnected grid structure of nickel-iron-cobalt medium-entropy alloy. Its mixing entropy is between traditional alloys and high-entropy alloys, which can effectively regulate the electronic structure of the material and reduce the reaction energy barrier. At the same time, the unique lattice distortion effect of medium-entropy alloy generates a large number of catalytic active sites at the atomic scale, fully exerting the unique cocktail effect of medium-entropy alloy. At the same time, its self-supporting characteristics avoid the use of adhesives in traditional electrodes, preventing the coverage of active sites and the shedding of catalysts under high current density, thus exhibiting higher alkaline OER catalytic activity and stability, and therefore can be used as a self-supporting "structure-integrated electrode" for oxygen evolution reaction for efficient and stable alkaline water electrolysis hydrogen production.

[0018] (3) The present application uses three-dimensional porous anodic aluminum oxide (3D-AAO) as a template and adopts template confinement induced co-electrodeposition method to design and construct a three-dimensional ordered nickel-iron-cobalt medium-entropy alloy grid film (denoted as 3D NiFeCo MEA NW), which is used as a structure-integrated electrode for high-current density OER. The preparation method can precisely control the diameter and length of the NiFeCo medium-entropy alloy nanowires by growing them in the confined environment of the template channels, forming a three-dimensional interconnected grid structure. The unique "structure-integrated" design of the electrode effectively solves the technical bottlenecks of mass transfer limitation and mechanical instability in traditional powder coated electrodes, significantly promoting the efficient penetration of electrolyte and rapid release of bubbles. At the same time, the preparation process is simple and mild, combining the composition advantages of medium-entropy alloys with the structural advantages of three-dimensional grids, maintaining low cost while providing an innovative electrode architecture solution for industrial-level high-current density water electrolysis hydrogen production systems.

[0019] (4) The synthetic electrocatalyst has better alkaline OER performance than commercial IrO2 at large current density, and the three-dimensional interconnected grid structure has stability and high specific surface area characteristics, which shows high activity and long-term stability at industrial current density in the electrocatalytic oxygen evolution reaction, and provides an innovative solution for the large-scale design and application of efficient and durable non-noble metal catalytic electrodes. The 3D NiFeCo MEA NW-1.5 h prepared in the application is used as a hydrogen production electrode in 1.0 M KOH electrolyte, and only 218.6 mV and 307.8 mV overpotential is required to drive 10 mA cm -2 and 500 mA cm -2 of current density, with a small Tafel slope and excellent long-term stability. The constructed 3D NiFeCo MEA NW-1.5 h is used as an anode to assemble an anion exchange membrane water electrolysis (AEMWE) electrolytic cell, which only requires an ultra-low cell voltage of 1.68 V to drive a high current density of 1000 mA cm - ², and maintains excellent stability for more than 160 hours of operation. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a synthesis flow chart of the 3D NiFeCo MEA NW structure integrated electrode of the application.

[0021] Figure 2 It is a structure characterization diagram of the 3D NiFeCo MEA NW-1.5 h prepared in Example 1; wherein (a) is an optical picture; (b) and (c) are SEM images under different magnifications; (d) is a TEM image; (e) is an HRTEM image; (f) is a corresponding element distribution diagram.

[0022] Figure 3 It is a composition characterization of the 3D Ni NW, 3D NiFe NW, 3D NiCo NW prepared in Comparative Examples 1-3, and the 3D NiFeCo MEA NW-1.5 h prepared in Example 1; wherein (a) is an XRD spectrum of the nanowire grid film of different element compositions; (b) is a Raman spectrum of the 3D NiFeCo MEA NW-1.5 h; (c), (d), (e), (f) are XPS energy spectra of Ni 2p, Fe 2p, Co 2p, O 1s of the 3D NiFeCo MEA NW-1.5 h, respectively.

[0023] Figure 4Characterization diagram of the OER electrocatalytic performance of 3D Ni NW, 3D NiFe NW, 3D NiCo NW prepared in Comparative Examples 1-3, 3DNiFeCo MEA NW-1.5 h prepared in Example 1, nickel foam (Ni Foam), and commercial IrO2 catalyst (20 wt%); (a) is the LSV curve after 90% iR compensation; (b) is 10 mA cm -2 , 100 mA cm -2 , 500 mA cm -2 (c) is the Tafel slope; (d) is the electrochemical impedance spectroscopy; (e) is the double layer capacitance C dl (f) 3DNiFeCo MEA NW-1.5 h and the existing OER catalyst at 10 mA cm −2 Performance comparison of overpotential and Tafel slope of current density; (g) 3D NiFeCo MEA NW-1.5 h at 500 mA cm -2 stability under .

[0024] Figure 5 Characterization and in situ spectra of the 3D NiFeCo MEA NW-1.5h prepared in Example 1 before and after the OER stability test; (a) is the TEM image after the stability test; (b) is the HRTEM image after the stability test; (c) is the comparison of XRD patterns before and after the stability test; (d), (e), (f), and (g) are the XPS energy spectra of Ni 2p, Fe 2p, Co 2p, and O1s after the stability test, respectively; (h) is the in situ Raman spectrum of the 3D NiFeCo MEA NW-1.5h reacting at different voltages.

[0025] Figure 6 Figure 3 is a performance diagram of anion exchange membrane water electrolysis (AEMWE) device; (a) is a schematic structural diagram of the AEMWE electrolyzer composed of 3DNiFeCo MEA NW-1.5h prepared in Example 1; (b) is the LSV curve of the AEMWE electrolyzer composed of 3D NiFeCoMEA NW-1.5h prepared in Example 1 at 60°C without iR compensation; (c) is a voltage-time stability comparison diagram of the AEMWE electrolyzer composed of 3DNiFeCo MEA NW-1.5h prepared in Example 1 without iR compensation. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with examples. All other examples obtained by those skilled in the art without creative labor based on the examples in the present application belong to the protection scope of the present application.

[0027] Example 1 The present example provides a preparation method of a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnecting mesh film. The preparation process is shown in Figure 1 , and specifically comprises the following steps: S1, taking a commercial Al sheet containing impurity Cu with a thickness of 0.1 mm, cutting it into 6 6 cm 2 , using a 0.3 M H3PO4 mixed solution as an electrolyte, the solvent of the electrolyte being composed of ethanol and deionized water in a volume ratio of 1:9, growing a 3D porous AAO layer on the Al sheet by anodic oxidation, and naturally forming a dense, non-porous barrier layer at the bottom of the 3D porous AAO layer close to the aluminum substrate; the anodic oxidation conditions are set as: an oxidation voltage of 190 V, a temperature of 2 ℃, and an oxidation time of 10 h; When the growth of the 3D porous AAO layer is about to end, the anodic oxidation voltage is gradually reduced by 5 V each time by using a continuous voltage reduction method, so that the oxidation current density is reduced to 0 mA cm -2 , and the anodic oxidation is stopped until the voltage is reduced to 50 V, the barrier layer is thinned, and a 3D-AAO / Al substrate is obtained; S2, after the 3D-AAO / Al substrate is washed with deionized water, it is immersed in a phosphoric acid solution with a mass fraction of 5 wt% at a temperature of 40 ℃ for 40 min, the barrier layer is further thinned, and after washing with deionized water, an expanded 3D-AAO / Al substrate is obtained; S3, using a two-electrode electrolytic cell, the expanded 3D-AAO / Al substrate is used as a cathode (the Al substrate is used as a current collector), a high-purity Ni sheet is used as an anode, a deposition solution is prepared by using deionized water as a solvent and containing 0.12 M NiSO4, 0.12 M NiCl2, 0.04 M FeSO4, 0.04 M CoSO4, 0.5 M H3BO3 and 0.1 mg / mL ascorbic acid, and a sulfuric acid solution is added dropwise to adjust the pH to 2.3. The deposition is carried out at a current density of 6 mA cm -2 for 1.5 h, and after the deposition is completed, the substrate is taken out and immersed in a 3 M NaOH solution to selectively etch away the remaining Al substrate and 3D expanded AAO layer, so as to prepare a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnecting mesh film, which is recorded as 3D NiFeCo MEA NW-1.5 h thin film.

[0028] Example 2 The embodiment provides a preparation method of a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnecting mesh film, and specifically comprises the following steps: S1, taking a commercial Al sheet containing impurity Cu, the thickness of the Al sheet is 0.15 mm, and the Al sheet is cut into 10 10 cm 2 pieces; 0.5 M H3PO4 mixed solution is used as an electrolyte, a solvent of the electrolyte is composed of ethanol and deionized water at a volume ratio of 1:9, a 3D porous AAO layer is grown on the Al sheet through anodic oxidation, and a dense and non-porous barrier layer is naturally formed at the bottom of the 3D porous AAO layer close to the aluminum substrate; an anodic oxidation condition is set as follows: an oxidation voltage is 195 V, a temperature is 0°C, and an oxidation time is 15 h; When the growth of the 3D porous AAO layer is about to end, a continuous pressure reduction method is used to gradually reduce the anodic oxidation voltage, the oxidation current density is reduced to 3 mA cm -2 -2 V each time, and the anodic oxidation is stopped until the voltage is reduced to 55 V, the barrier layer is thinned, and a 3D-AAO / Al substrate is obtained; S2, the 3D-AAO / Al substrate is cleaned with deionized water and then immersed in a 10 wt% phosphoric acid solution at a temperature of 45°C for 50 min, the barrier layer is further thinned, and after being cleaned with deionized water, an expanded 3D-AAO / Al substrate is obtained; S3, an expanded 3D-AAO / Al substrate is used as a cathode (an Al substrate is used as a current collector), a high-purity Ni sheet is used as an anode, a deionized water is used as a solvent of an electrodeposition solution, the electrodeposition solution contains 0.12 M NiSO4, 0.12 M NiCl2, 0.04 M FeSO4, 0.04 M CoSO4, 0.5 M H3BO3 and 0.1 mg / mL ascorbic acid, and a sulfuric acid solution is added dropwise to adjust the pH to 2.3, and the electrodeposition is performed at a current density of 8 mA cm -2 -2 for 1 h, the electrodeposition is completed, the expanded 3D-AAO / Al substrate is taken out and immersed in a 5 M NaOH solution, the remaining Al substrate and the 3D expanded AAO layer are selectively etched, and a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnecting mesh film is prepared, which is denoted as 3DNiFeCo MEA NW-1 h film.

[0029] Embodiment 3 The embodiment provides a preparation method of a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnecting mesh film, and specifically comprises the following steps: S1, taking a commercial Al sheet containing impurity Cu, the thickness of the Al sheet is 0.15 mm, and the Al sheet is cut into 10 10 cm 2, 0.2 M H3PO4 mixed solution is used as the electrolyte, the solvent of the electrolyte is composed of ethanol and deionized water in a volume ratio of 1:9, a 3D porous AAO layer is grown on the Al sheet by anodization, and a dense and non-porous barrier layer is naturally formed at the bottom of the 3D porous AAO layer close to the aluminum substrate; the anodization conditions are set as follows: an oxidation voltage of 192 V, a temperature of 5°C, and an oxidation time of 20 h; When the growth of the 3D porous AAO layer is about to end, the anodization voltage is gradually reduced by 2 V each time using the continuous voltage reduction method, so that the oxidation current density is reduced to 1 mA cm -2 , and the anodization is stopped after the voltage is reduced to 52 V, the barrier layer is thinned, and a 3D-AAO / Al substrate is obtained; S2, the 3D-AAO / Al substrate is cleaned with deionized water and then immersed in a 3 wt% phosphoric acid solution at a temperature of 50°C for 60 min, the barrier layer is further thinned, and after cleaning with deionized water, a 3D-AAO / Al substrate with an expanded hole is obtained; S3, using a two-electrode electrolytic cell, the 3D-AAO / Al substrate with an expanded hole is used as the cathode (the Al substrate as the current collector), a high-purity Ni sheet is used as the anode, the electrodeposition solution is deionized water as the solvent, containing 0.12 M NiSO4, 0.12 M NiCl2, 0.04 M FeSO4, 0.04 M CoSO4, 0.5 M H3BO3 and 0.1 mg / mL ascorbic acid, and a sulfuric acid solution is added dropwise to adjust the pH to 2.3. Deposition is carried out at a current density of 3 mA cm -2 for 3 h, and after deposition, it is immersed in a 1 M NaOH solution to selectively etch away the remaining Al substrate and 3D expanded AAO layer, to obtain a nickel-iron-cobalt mesoporous alloy nanowire three-dimensional interconnecting mesh film, denoted as 3D NiFeCo MEA NW-3 h thin film.

[0030] Comparative Example 1 This comparative example provides a preparation method of a single metal nanowire three-dimensional interconnecting mesh film, and the specific steps refer to Example 1, and the only difference is that in step S3, the electrodeposition solution is deionized water as the solvent, containing NiSO4 (0.12 M), NiCl2 (0.12 M), H3BO3 (0.5 M) and ascorbic acid (0.1 mg / mL), and a sulfuric acid solution is added dropwise to adjust the pH to 2.3. Finally, a nickel nanowire three-dimensional interconnecting mesh film is prepared, denoted as 3D Ni NW thin film.

[0031] Comparative Example 2 The comparative example 1 provides a preparation method of a bimetallic nanowire three-dimensional interconnected mesh film. The specific steps refer to those of the example 1, except that the electrodeposition solution in step S3 contains NiSO4 (0.12 M), NiCl2 (0.12 M), CoSO4 (0.04 M), H3BO3 (0.5 M) and ascorbic acid (0.1 mg / mL) as solvents, and a small amount of sulfuric acid solution is added to adjust the pH to 2.3. Finally, a nickel-cobalt alloy nanowire three-dimensional interconnected mesh film is prepared, which is denoted as 3D NiCo NW film.

[0032] Comparative example 3 The comparative example 1 provides a preparation method of a bimetallic nanowire three-dimensional interconnected mesh film. The specific steps refer to those of the example 1, except that the electrodeposition solution in step S3 contains NiSO4 (0.12 M), NiCl2 (0.12 M), CoSO4 (0.04 M), H3BO3 (0.5 M) and ascorbic acid (0.1 mg / mL) as solvents, and a small amount of sulfuric acid solution is added to adjust the pH to 2.3. Finally, a nickel-cobalt alloy nanowire three-dimensional interconnected mesh film is prepared, which is denoted as 3D NiCo NW film.

[0033] Performance test: The samples were characterized by scanning electron microscope transmission (SEM), transmission electron microscope (TEM), X-ray diffraction spectrum (XRD), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive spectroscopy (EDS) and other technologies. In 1.0 M KOH, electrochemical tests were carried out by using a standard three-electrode test system. The prepared NiFeCo entropic alloy, Hg / HgO electrode and graphite rod electrode were used as working electrode, reference electrode and counter electrode respectively. The rate of linear sweep voltammetry (LSV) test was 2 mVs -1 . The frequency range of electrochemical impedance (EIS) test was 100 kHz to 0.01 Hz, and the amplitude was 5 mV. The potential range of cyclic voltammetry (CV) test was non-faradic region (0.926~1.026 V vs. RHE), and the scan rate range was 20~100 mV s -1 , to obtain the electrochemical double-layer capacitance (C dl ) of the catalyst.

[0034] (1) Morphology and structure characterization of electrode

[0035] Figure 1This is a flow chart for the synthesis of the 3D NiFeCo MEA NW structured integrated electrode. First, the 3D AAO template is pore-enlarged, followed by a one-step co-electrodeposition process to create a three-dimensional interconnected NiFeCo medium-entropy alloy nanowire mesh. This method is not only simple and requires mild conditions, but also enables the large-scale, controllable preparation of the integrated electrode.

[0036] Figure 2 Figure 1 shows the structure of the 3D NiFeCo MEA NW-1.5h prepared in Example 1; (a) is an optical image, confirming that the preparation method of this application can achieve large-scale, controllable preparation of integrated electrodes. Scanning electron microscopy (SEM) images show that the prepared 3D NiFeCo MEA NW-1.5h is approximately 15 μm thick, with uniformly grown vertical nanowires with a diameter of approximately 200 nm, connected by horizontal nanowires, and a large number of pores ( Figure 2 (b) and Figure 2 (c)). Transmission electron microscopy (TEM) images more clearly show the interconnected structure of vertical nanowires and lateral nanowires ( Figure 2 (d)). In the high-resolution transmission electron microscopy (HRTEM) image of 3DNiFeCo MEA NW-1.5 h ( Figure 2 (e)) lattice fringes with a spacing of 0.204 nm were observed, corresponding to the (111) plane of the FCC crystal structure. TEM images and XRD test results show that 3D NiFeCoMEA NW-1.5 h has a highly crystalline FCC structure. In addition, energy dispersive spectroscopy (EDS) images ( Figure 2 (f) shows that the Ni, Fe, and Co elements are evenly distributed, further confirming the successful preparation of 3D NiFeCo MEA NW-1.5 h. The final composition ratio of Ni:Fe:Co is 30.8:38.8:30.4 using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the mixing entropy ΔS mix =1.092 R>R, which conforms to the medium entropy characteristic.

[0037] Figure 3 Compositional characterization of the 3D NiFeCo MEA NW-1.5 h prepared in Example 1; (a) is the XRD structural characterization of the nanowire mesh membrane composed of different elements. The clear diffraction peaks at 44.18°, 51.43°, and 75.7° correspond to the (111), (200), and (220) crystal planes of the Ni face-centered cubic (FCC) structure (PDF#00-04-085), respectively. The diffraction peak position shifts slightly to the left because the addition of other elements to the lattice will cause lattice distortion. Raman spectroscopy provides a more sensitive means for observing the surface of medium entropy alloys. Raman spectroscopy (Figure 3 (b) shows that 3D NiFeCo MEA NW-1.5 h has no obvious Raman characteristic peak at 800 cm -1 There is a broad peak at the surface, which may be due to the presence of some oxides on the surface. In order to further explore the surface chemical bonding state of the sample, X-ray photoelectron spectroscopy (XPS) characterization was performed. The Ni2 p spectrum of the 3D NiFeCo MEA NW-1.5 h surface was analyzed ( Figure 3 (c)), by Ni 2p 3 / 2 (855.9 eV), Ni 2p 1 / 2 (873.6 eV) consists of two spin-orbit pairs and two satellite peaks (abbreviated as "sat."), indicating the presence of Ni 2+ , while the secondary peaks at 852.1 eV and 869.2 eV are attributed to metallic Ni. Similarly, the deconvoluted peaks at 710.8 eV and 723.9 eV and the two satellite peaks in the Fe 2p distribution can be attributed to Fe 3+ The peaks at 706.8 eV and 719.6 eV are attributed to metallic Fe. Due to the high content of Ni in the sample, the broad peak at around 712.5 eV can be attributed to the Auger peak of Ni LMM ( Figure 3 (d)). At the same time, Co 2p 3 / 2 Peak and 2p 1 / 2 The peaks are at 781.1 eV and 796.8 eV, respectively, which are similar to those of Co 3+ The binding energies of the components are consistent, and the peaks at 777.8 eV and 792.9 eV are attributed to metal Co ( Figure 3 (e)). The O 1s spectrum can be decomposed into three different peaks ( Figure 3 (f)), namely, there are three characteristic peaks at 529.6 eV, 531.4 eV, and 532.6 eV, which are labeled as MO, M-OH, and absorbed H2O, respectively. Therefore, the XPS test results reveal the metallic bonding nature of 3D NiFeCo MEA NW-1.5h and have the expected surface oxidation.

[0038] (2) Oxygen evolution reaction performance

[0039] Using 1.0 M KOH solution as the electrolyte, a typical three-electrode test system was used to investigate the OER performance of nickel foam (Ni Foam), 3D Ni NW, 3D NiFe NW, 3D NiCo NW, 3D NiFeCo MEA NW-1.5 h, and commercial IrO2 catalysts (20 wt%). Linear sweep voltammetry (LSV) curves ( Figure 4(a) shows that the OER activity of the 3D NiFeCo MEA NW-1.5 h electrode is much better than that of other synthesized electrodes, and even better than that of the commercial IrO2 catalyst. The overpotential of the 3D NiFeCo MEA NW-1.5 h at 10, 100 and 500 mA cm -2 was 218.6, 260.6 and 307.8 mV, respectively, which was significantly better than that of other catalysts Figure 4 (b) shows the excellent electrocatalytic activity. It is worth noting that the oxygen evolution reaction (OER) performance of the 3D NiFeCo MEA NW-1.5 h is significantly better than that of the 3D NiCo NW and 3D NiFe NW at the same current density, which is attributed to the multi-element synergistic "cocktail effect" unique to the medium-entropy alloy. At the same time, the OER performance of the 3D NiFeCo MEA NW-1 h and 3D NiFeCo MEA NW-3 h prepared in Examples 2 and 3, respectively, was tested. The overpotential of the 3D NiFeCo MEA NW-1 h at 10, 100 and 500 mA cm -2 was 239.9, 279.8 and 326.1 mV, respectively; and the overpotential of the 3D NiFeCo MEA NW-3 h at 10, 100 and 500 mA cm -2 was 231.3, 274.7 and 329.7 mV, respectively, all of which show excellent electrocatalytic activity.

[0040] Figure 4 (c) shows the Tafel slope corresponding to the polarization curve, which further deepens the understanding of the OER kinetics. In the low current density region, the Tafel slope of the 3D NiFeCo MEA NW-1.5 h electrode is 37.8 mV dec -1 , which is better than that of the commercial IrO2 (52.9 mV dec -1 ); at the same time, at a large current density, the Tafel slope of the 3D NiFeCo MEA NW-1.5 h electrode is only 71.2 mV dec -1 , which is much better than that of IrO2 (138.1 mV dec -1 ), indicating that the material can still maintain a fast reaction kinetics process at a high current density and has a high mass transfer efficiency. Figure 4 (d) shows the EIS results, which also verify this result, in which the 3D NiFeCo MEA NW-1.5 h shows the smallest Nyquist circle radius and charge transfer resistance (R ct ), confirming that it has excellent electron conduction ability and high efficient charge transfer kinetics. In addition, based on the double-layer capacitance (C dl) The estimated electrochemical active surface area (ECSA) analysis showed that ( Figure 4 (e) ), C of 3D NiFeCo MEA NW-1.5 h dl 12.87 mF cm -2 , which is higher than that of 3D NiNW (10.14 mF cm -2 )、IrO2 / NF(6.07 mF cm -2 ) and pure nickel foam (3.28 mF cm -2 ), which is due to its three-dimensional interconnected grid structure that effectively exposes abundant active sites. Through systematic comparison with the state-of-the-art advanced OER catalysts ( Figure 4 (f) 3D NiFeCo MEA NW-1.5 h at Tafel slope and 10 mA cm -2 In addition, stability is a key criterion for evaluating electrocatalysts, such as Figure 4 As shown in (g), the stability of the prepared sample was evaluated by constant current testing. Only 1.56 V (vs. RHE) potential was required to drive 500 mA cm -2 The high current density of 1.5 GHz was achieved and the performance remained stable after 400 hours of continuous operation with negligible performance degradation, indicating excellent long-term stability even at high current density. Based on the above analysis and prior art OER catalysts, it can be seen that the 3D NiFeCo MEA NW-1.5 h catalyst prepared in this application has superior OER catalytic activity and stability under alkaline conditions.

[0041] (3) Internal mechanism of oxygen evolution reaction

[0042] In order to further explore the fundamental reason for the excellent OER performance of 3D NiFeCo MEA NW-1.5 h catalyst, this application characterized the samples after OER stability test. TEM image ( Figure 5 (a)) confirmed that the three-dimensional nanowire structure of the material was completely preserved under harsh reaction conditions, and an ultra-thin reconstruction layer was formed on the surface. In order to further confirm the structure of the reconstruction layer, this application used HRTEM ( Figure 5 (b) Characterization of the 3D NiFeCo MEA NW-1.5 h after the reaction showed that the 0.204 nm lattice fringes in the nanowire core correspond to the (111) crystal plane of the NiFeCo medium entropy alloy, while there is an ultra-thin (2-5 nm) reconstruction layer on the surface with a lattice fringe spacing of 0.208 nm, which belongs to the highly active Ni(FeCo)OOH phase. No hydroxide was observed deep inside the nanowire, further confirming that the reconstruction was uniformly covered only on the surface of the nanowire. XRD spectrum ( Figure 5(c) shows that the crystal structure is stable and there is no phase change before and after the reaction, which is consistent with the result observed by HRTEM that the thickness of the surface confined reconstruction layer (2-5 nm) is much lower than the XRD detection depth (~μm level). XPS was used to further understand the chemical composition and oxidation state of the 3D NiFeCo MEA NW-1.5 h reconstruction layer. It is worth noting that there is a significant difference between the XPS test results before the stability test. The surface metallic Ni / Fe / Co signal completely disappears and transforms into a high valence state. After argon ion etching, the core metallic state characteristics gradually emerge ( Figure 5 (d), (e), (f)). Correspondingly, in the O 1s spectrum ( Figure 5 (g)), the peak intensity decreases with increasing etching depth. The depth profile results show that there are oxidized Ni, Fe and Co and hydroxide groups on the surface of the nanowires, and metallic Ni, Fe and Co in the core. It can be considered that the core of the medium-entropy alloy nanowires has a highly crystalline metal phase and is a good electron conductor; the hydroxide oxide on the surface of the medium-entropy alloy nanowires is conducive to promoting The binding and catalytic activity of OH are enhanced, while the ultrathin thickness of the reconstruction layer ensures efficient electron transfer from the surface to the core. In situ Raman spectroscopy analysis was used to further explore the evolution of the OER active sites and the dynamic self-reconstruction process of 3D NiFeCoMEA NW-1.5 h. Figure 5 (h)), no obvious Raman signal was detected at low potential, indicating that the initial state of the material was an unreconstructed metallic state. When the potential was increased to 1.35 V, two new peaks appeared: at 476 cm -1 δ(Ni 3+ -O) bending vibration peak and 552 cm -1 ν(Ni 3+ -O) stretching vibration peaks corresponding to the E g Bending vibration and A 1g Stretching vibration bond. When the potential rises to 1.65 V, the two main peaks shift to the right, that is, the OER reaction is accompanied by partial structural reorganization of the Fe / Co site. In summary, this application finally determined that the essence of the high performance of OER is derived from the formation of a core-shell structure of the ultra-thin ordered heterojunction of NiFeCo medium entropy alloy-Ni(FeCo)OOH. Ni(FeCo)OOH is uniformly covered on the surface of the nanowire, forming a "passivation protection" under alkaline conditions, thereby protecting the 3D NiFeCo MEA NW-1.5 h from further corrosion in alkaline and oxidizing environments, and improving mechanical and electrochemical stability. The oxyhydroxide of the reconstructed layer has a small lateral size and ultra-thin thickness, which can greatly reduce the transmission resistance of electrons from the surface catalyst to the conductive core, thereby greatly enhancing the charge transfer in the OER process, which is conducive to accelerating the reaction kinetics. This surface confined reconstruction strategy provides a new paradigm for the design of efficient and stable OER catalysts.

[0043] (4) Anion exchange membrane water electrolysis (AEMWE) device performance

[0044] The NiFeCo MEA NW-1.5 h electrode with a three-dimensional self-supporting structure constructed in Example 1 was used as the anode (titanium felt was used as the diffusion layer), and Pt-coated carbon paper (Pt loading 1 mg cm -2 , Pt / CP) as cathode, and assemble the AEMWE device ( Figure 6 (a)). The control group used Ir-coated titanium felt (Ir loading 2 mg cm -2 , Ir / TF) as the anode and Pt / CP as the cathode. Polarization curves were measured at 60°C with 1.0 M KOH solution circulating on the anode side. The results show that the NiFeCo MEA NW / TF || Pt / CP electrolyzer can achieve 500 mA cm at voltages of only 1.60 and 1.68 V. -2 and 1000 mA cm -2 The high current density (without iR compensation) is significantly better than that of Ir / TF || Pt / CP, reaching 500 mA cm -2 The required 1.81 V ( Figure 6 (b)). More importantly, the electrolyzer based on NiFeCoMEA NW-1.5 h assembly was -2 After running for more than 160 hours at a high current density, it still showed excellent stability ( Figure 6 (c)). This result demonstrates that the 3D NiFeCo MEA NW-1.5 h electrode has efficient and stable catalytic ability under harsh conditions, showing good prospects for industrial application.

[0045] In summary, compared with the prior art, the preparation method and application of the three-dimensional ordered NiFeCo medium entropy alloy grid thin film electrode proposed in the present invention have the following technical advantages: 1. The transition metal-based medium-entropy alloy electrode proposed in the present invention adopts the method of template confinement induced electrodeposition to construct a three-dimensional grid film composed of interconnected NiFeCo medium-entropy alloy nanowires. This not only builds an efficient electron transport network for the catalytic electrode, improves the mass transfer efficiency, and provides abundant active sites, but also increases the overall mechanical strength of the electrode, making the catalyst highly stable.

[0046] 2. This invention solves the cumbersome process of preparing medium-entropy alloy electrodes, enabling the low-cost, green, and large-scale production of AEMWE anode electrodes. The resulting electrodes exhibit both high catalytic activity and excellent stability, potentially accelerating the commercialization of hydrogen production technology using anion exchange membrane water electrolysis.

[0047] 3. The new electrode material successfully developed by the application exhibits excellent oxygen evolution reaction (OER) activity beyond commercial IrO2, providing a new method for designing low-cost, high-stability non-noble metal catalyst systems. In addition, the unique three-dimensional ordered structure and synergistic optimization mechanism of the electrode can open up new ideas for the research and development of new generation flexible zinc air batteries, supercapacitors and other clean energy devices.

[0048] Those skilled in the art will understand that the above description is only several specific embodiments of the application, not all embodiments. It should be noted that many modifications and improvements can also be made by those skilled in the art, and all modifications or improvements that do not exceed the scope of the claims should be considered as the protection scope of the application.

Claims

1. A method for preparing a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires, characterized in that: The steps include: S1. Cutting a commercial Al sheet containing Cu impurities and performing anodization to grow a 3D porous AAO layer on the Al sheet. When the growth is about to end, the anodization voltage is gradually reduced by a continuous step-down method to obtain a 3D-AAO / Al substrate. S2, immersing the 3D-AAO / Al substrate in a phosphoric acid solution to obtain a 3D-AAO / Al substrate with expanded pores; S3. The expanded 3D-AAO / Al substrate is placed in an electrodeposition solution containing nickel salt, iron salt and cobalt salt for electrodeposition. The three metals in the deposited alloy nanowires have an almost equal atomic ratio. The Al substrate and the 3D expanded AAO layer are removed to obtain a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires, which is recorded as a 3D NiFeCo MEA NW film.

2. The method for preparing the nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected grid film according to claim 1, characterized in that: The thickness of the commercial Al sheet containing Cu impurities in step S1 is 0.1~0.2 mm, and the size after cutting is (5~10) (5~10) cm 2 .

3. The method for preparing the nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected grid film according to claim 1, characterized in that: During the anodization in step S1, a 0.2-0.5 M H3PO4 mixed solution is used as the electrolyte. The solvent of the electrolyte is composed of ethanol and deionized water in a volume ratio of 1:

9. The anodization parameters are set as follows: oxidation voltage of 190-195 V, temperature of 0-5°C, and oxidation time of 10-20 h.

4. The method for preparing a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1 or 3, characterized in that: In step S1, the anodic oxidation voltage is gradually reduced by a continuous voltage reduction method, and the anodic oxidation voltage is reduced by 2-5 V each time until the current density drops to 0-3 mA cm -2 , stop anodic oxidation when the voltage drops to 50~55 V.

5. The method for preparing the nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected grid film according to claim 1, characterized in that: In step S2, the 3D-AAO / Al substrate is cleaned with deionized water and then immersed in a phosphoric acid solution with a temperature of 40-50° C. and a concentration of 3-10 wt % for 40-60 min.

6. The method for preparing a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1, characterized in that: In step S3, a two-electrode electrolytic cell is used for electrodeposition, the expanded 3D-AAO / Al substrate is used as the cathode, the Al substrate is used as the current collector, the high-purity Ni sheet is used as the anode, and the solution containing nickel salt, iron salt and cobalt salt is used as the electrodeposition solution. -2 The deposition was carried out at a current density of 1~3 h.

7. The method for preparing a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1 or 6, characterized in that: The electrodeposition solution uses deionized water as a solvent, contains 0.12 M NiSO4, 0.12 M NiCl2, 0.04 M FeSO4, 0.04 M CoSO4, 0.5 M H3BO3 and 0.05 mg / mL-0.2 mg / mL ascorbic acid, and the pH is adjusted to 2.0-3.

0.

8. The method for preparing a three-dimensional interconnected grid film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1, characterized in that: In step S3, the electrodeposited product is placed in a 1-5 M NaOH solution, and the Al substrate and the 3D expanded pore AAO layer are removed by chemical etching.

9. A three-dimensional interconnected nickel-iron-cobalt medium-entropy alloy nanowire mesh film produced by the method for producing a three-dimensional interconnected nickel-iron-cobalt medium-entropy alloy nanowire mesh film according to any one of claims 1 to 8.

10. Use of the nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected grid membrane according to claim 9 as a self-supporting integrated alkaline oxygen evolution reaction electrode in industrial water electrolysis for hydrogen production.

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