Ni-Fe-Co entropic alloy nanowire three-dimensional interconnection grid film, preparation method and application thereof

Abstract

The application belongs to the technical field of catalytic materials, and particularly relates to a nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnected mesh film, a preparation method and application. The application uses an aluminum sheet containing copper impurities as a substrate, anodically oxidizes to obtain a three-dimensional ordered porous aluminum oxide template, then direct current co-electrodeposits to prepare nickel-iron-cobalt entropy alloy nanowires in a pore channel limit, removes the aluminum substrate and the 3D- AAO template to obtain a nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnected mesh film. The material is based on a mixed entropy effect and a structure integration design, can be directly used as a self-supporting electrode for efficient and stable electrolytic water oxygen evolution, the three-dimensional mesh structure and the self-supporting characteristics promote electrolyte transmission and gas product desorption, improve mass transfer efficiency, avoid the use of traditional adhesives, and enhance electrode stability. The application solves the problems of high energy consumption in synthesizing existing entropy alloy catalysts, poor catalytic activity under industrial-grade large-current working conditions, and active substance shedding in the reaction.

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 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 not only significantly improves the mass transfer efficiency by promoting the efficient transport of electrolyte and the rapid desorption of electrolytic water product gas, but also avoids 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 nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film, comprising the following steps:

[0007] S1, cut the commercial Al sheet containing impurity Cu and perform anodic oxidation to grow a 3D porous AAO layer on the Al sheet, and when the growth is about to end, gradually reduce the anodic oxidation voltage by using a continuous pressure reduction method to obtain a 3D-AAO / Al substrate;

[0008] S2, immerse the 3D-AAO / Al substrate in a phosphoric acid solution to obtain an expanded 3D-AAO / Al substrate;

[0009] S3, perform electrodeposition on the expanded 3D-AAO / Al substrate in an electrodeposition solution containing nickel salt, iron salt and cobalt salt, the deposited alloy nanowire has a near-equiatomic ratio of the three metals, remove the Al substrate and the 3D expanded AAO layer, and prepare a nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film, denoted as 3D NiFeCo MEA NW thin film.

[0010] Further improvement of the preparation method of nickel-iron-cobalt medium entropy alloy nanowire three-dimensional interconnected mesh film:

[0011] 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 .

[0012] 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.

[0013] Preferably, in step S1, the anodic oxidation voltage is gradually reduced by using a continuous pressure reduction method, and the anodic oxidation voltage is reduced by 2-5 V each time until the current density is reduced to 0-3 mA cm -2, the voltage drops to 50-55 V, and the anodization stops.

[0014] Preferably, in step S2, the 3D-AAO / Al substrate is cleaned with deionized water and then immersed in a phosphoric acid solution with a concentration of 3-10 wt% at a temperature of 40-50 ℃ for 40-60 min.

[0015] Preferably, in step S3, a two-electrode electrolytic cell is used for electrodeposition, the 3D-AAO / Al substrate is used as the cathode, an Al substrate is used as the current collector, a high-purity Ni sheet is used as the anode, and a solution containing nickel salt, iron salt and cobalt salt is used as the electrodeposition solution, and the deposition is performed at a current density of 3-8 mA cm -2 for 1-3 h.

[0016] Preferably, the electrodeposition solution contains 0.12 M of NiSO4, 0.12 M of NiCl2, 0.04 M of FeSO4, 0.04 M of CoSO4, 0.5 M of H3BO3 and 0.05 mg / mL-0.2 mg / mL of ascorbic acid, and the pH is adjusted to 2.0-3.0.

[0017] Preferably, in step S3, the electrodeposited product is placed in a 1-5 M NaOH solution, and the Al substrate and the 3D-AAO layer are removed by chemical etching.

[0018] The second object of the present application is to provide a nickel-iron-cobalt entropic alloy nanowire three-dimensional interconnecting mesh film prepared by the preparation method of the nickel-iron-cobalt entropic alloy nanowire three-dimensional interconnecting mesh film.

[0019] The third object of the present application is to provide an application of the nickel-iron-cobalt entropic alloy nanowire three-dimensional interconnecting mesh film as a self-supporting integrated alkaline OER reaction electrode in industrial water electrolysis hydrogen production.

[0020] The present application has the following beneficial effects compared with the prior art:

[0021] (1) The present application relates to a kind of nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnection grid structure film (denoted as 3DNiFeCo MEA NW) construction method, the invention first uses the aluminum sheet containing certain copper impurity is anodized, grows a layer of three-dimensional ordered porous anodic aluminum oxide (3D-AAO) with vertical channel and horizontal channel interconnection on Al sheet, a dense, non-porous barrier layer is formed naturally at the bottom of three-dimensional porous AAO layer close to aluminum substrate;During anodization, the thickness of barrier layer is proportional to the applied voltage (usually about 1 nm / V), the barrier layer formed under constant high voltage (190 V) is very thick (about 190 nm). When anodization is about to end, the voltage is gradually reduced to 50 V using continuous voltage reduction method, so that the barrier layer occurs mild and controllable electrochemical dissolution / reconstruction, and the thickness is reduced to about 50 nm, and the 3D-AAO / Al substrate with thinned barrier layer is obtained. 3D-AAO / Al substrate is placed in 3-10 wt% phosphoric acid solution with temperature of 40-50 DEG C, and the barrier layer is further thinned (to ensure its penetrability) and the pore size of AAO channel is slightly enlarged, to obtain the hole-enlarged 3D-AAO / Al substrate, to create conditions for subsequent electrodeposition of nanomaterial. The concentration ratio of nickel-iron-cobalt ternary metal electrolyte is accurately controlled, and the nickel-iron-cobalt entropy alloy nanowire with mixed entropy characteristics is constructed by direct current co-electrodeposition in channel confined channel;Subsequently, the aluminum substrate and AAO template are selectively etched and removed, and deionized water is washed and dried, and finally the nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnection grid film is obtained. In the initial stage of OER reaction, the surface of NiFeCo entropy alloy is restructured, and an ultrathin Ni (FeCo) OOH coating layer is generated, forming an ordered heterojunction core-shell structure. This structure plays a dual role in alkaline environment: on the one hand, it forms a passivation protective layer, effectively preventing the nanowire from being corroded under harsh alkaline and oxidative conditions, significantly improving the mechanical and electrochemical stability of the structure;On the other hand, it provides abundant active sites and enhances the electrochemical intrinsic activity.

[0022] (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 efficient and stable alkaline water electrolysis hydrogen production.

[0023] (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.

[0024] (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

[0025] Figure 1 It is a synthesis flow chart of the 3D NiFeCo MEA NW structure integrated electrode of the application.

[0026] 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.

[0027] 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.

[0028] Figure 4The following are characterization graphs 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, as well as Ni Foam and a commercial IrO2 catalyst (20 wt%); where (a) is the LSV curve after 90% iR compensation; and (b) is the curve at 10 mA cm⁻¹. -2 100 mA cm -2 500 mA cm -2 (c) Overpotential comparison; (d) Tafel slope; (e) Electrochemical impedance spectroscopy; (f) Double layer capacitance C dl (f) shows the effect of 3DNiFeCo MEA NW-1.5 h on the OER catalyst of existing technology at 10 mA cm⁻¹. −2 Performance comparison of overpotential and Tafel slope at current density; (g) is 3D NiFeCo MEA NW-1.5 h at 500 mA cm⁻¹ -2 Stability under [condition / condition].

[0029] Figure 5 Characterization and in-situ spectra of 3D NiFeCo MEA NW-1.5 h prepared in Example 1 before and after OER stability testing; (a) is the TEM image after stability testing; (b) is the HRTEM image after stability testing; (c) is a comparison of XRD patterns before and after stability testing; (d), (e), (f), and (g) are the XPS spectra of Ni 2p, Fe 2p, Co 2p, and O1s after stability testing, respectively; (h) is the in-situ Raman spectrum of 3D NiFeCo MEA NW-1.5 h reacting under different voltages.

[0030] Figure 6 The following are performance diagrams of anion exchange membrane water electrolysis (AEMWE) devices: (a) is a schematic diagram of the AEMWE electrolyzer composed of 3DNiFeCo MEA NW-1.5 h prepared in Example 1; (b) is the LSV curve of the AEMWE electrolyzer composed of 3D NiFeCoMEA NW-1.5 h prepared in Example 1 at 60℃ without iR compensation; (c) is a comparison diagram of the voltage-time stability of the AEMWE electrolyzer composed of 3DNiFeCo MEA NW-1.5 h prepared in Example 1 without iR compensation. Detailed Implementation

[0031] 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 in combination with embodiments, and all other embodiments obtained by those skilled in the art without creative labor on the basis of the embodiments in the present application belong to the protection scope of the present application.

[0032] Embodiment 1

[0033] The embodiment provides a preparation method of a nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnection grid film, and a preparation flow is as shown in Figure 1 The embodiment provides a preparation method of a nickel-iron-cobalt entropy alloy nanowire three-dimensional interconnection grid film, and a preparation flow is as shown in

[0034] S1, taking a commercial Al sheet containing impurity Cu, the thickness is 0.1 mm, and the Al sheet is cut into 6 6 cm 2 A 0.3 M H3PO4 mixed solution is used as an electrolyte, a solvent of the electrolyte is composed of ethanol and deionized water according to a volume ratio of 1:9, a 3D porous AAO layer is grown on the Al sheet by 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; anodic oxidation conditions are set as follows: an oxidation voltage is 190 V, a temperature is 2 ℃, and an oxidation time is 10 h;

[0035] 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 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;

[0036] S2, after the 3D-AAO / Al substrate is cleaned with deionized water, the 3D-AAO / Al substrate is immersed in a 5 wt% phosphoric acid solution with a temperature of 40 ℃ for 40 min, the barrier layer is further thinned, and after being cleaned with deionized water, a reamed 3D-AAO / Al substrate is obtained;

[0037] S3, using a two-electrode electrolytic cell, taking the reamed 3D-AAO / Al substrate as a cathode (the Al substrate as a current collector), taking a high-purity Ni sheet as an anode, taking deionized water as a solvent of an electrodeposition solution, and adding 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 adding a sulfuric acid solution dropwise to adjust the pH to 2.3. The electrodeposition solution is electrolyzed at 6 mA cm -2Electrodeposition was carried out at a current density of 1.5 h. After the electrodeposition was completed, the material was removed and immersed in a 3 M NaOH solution to selectively etch away the remaining Al substrate and the 3D expanded pore AAO layer, thus obtaining a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires, denoted as 3D NiFeCo MEA NW-1.5 h film.

[0038] Example 2

[0039] This embodiment provides a method for preparing a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires, specifically including the following steps:

[0040] S1. Take a commercially available Al sheet containing Cu impurities, with a thickness of 0.15 mm, and cut it into 10 pieces. 10 cm 2 A 0.5 M H3PO4 mixed solution was used as the electrolyte. The electrolyte solvent consisted of ethanol and deionized water in a volume ratio of 1:9. Anodizing was used to grow a 3D porous AAO layer on the Al sheet. A dense, non-porous barrier layer was naturally formed at the bottom of the 3D porous AAO layer near the aluminum substrate. The anodizing conditions were set as follows: oxidation voltage of 195 V, temperature of 0 °C, and oxidation time of 15 h.

[0041] As the growth of the 3D porous AAO layer neared completion, the anodic oxidation voltage was gradually reduced using a continuous voltage reduction method, decreasing by 2 V each time, until the oxidation current density was reduced to 3 mA cm⁻¹. -2 Anodizing was stopped when the voltage dropped to 55 V, the barrier layer was thinned, and a 3D-AAO / Al substrate was obtained.

[0042] S2. After washing the 3D-AAO / Al substrate with deionized water, it was immersed in a 10 wt% phosphoric acid solution at 45°C for 50 min. The barrier layer was further thinned. After washing with deionized water, the pore-expanded 3D-AAO / Al substrate was obtained.

[0043] S3. A two-electrode electrolytic cell was used, with a pore-expanded 3D-AAO / Al substrate as the cathode (Al substrate as the current collector) and a high-purity Ni sheet as the anode. The electrodeposition solution used deionized water as the solvent and contained 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. Sulfuric acid solution was added dropwise to adjust the pH to 2.3. The electrodeposition was carried out at 8 mA cm⁻¹. -2S1, a commercial Al sheet containing impurity Cu was taken, with a thickness of 0.2 mm, and cut into 8

[0044] Example 3

[0045] The embodiment provides a preparation method of a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interlinked mesh film, and specifically comprises the following steps:

[0046] S1, a commercial Al sheet containing impurity Cu was taken, with a thickness of 0.2 mm, and cut into 8 8 cm 2 , 0.2 M H3PO4 mixed solution was used as an electrolyte, the solvent of the electrolyte was composed of ethanol and deionized water in a volume ratio of 1:9, a 3D porous AAO layer was grown on the Al sheet by anodic oxidation, and a dense, non-porous barrier layer was naturally formed at the bottom of the 3D porous AAO layer close to the aluminum substrate; the anodic oxidation conditions were set as follows: an oxidation voltage of 192 V, a temperature of 5 DEG C, and an oxidation time of 20 h;

[0047] When the growth of the 3D porous AAO layer was about to end, a continuous voltage reduction method was used to gradually reduce the anodic oxidation voltage, and the oxidation current density was reduced to 1 mA cm -2 , and the anodic oxidation was stopped until the voltage was reduced to 52 V, the barrier layer was thinned, and a 3D-AAO / Al substrate was obtained;

[0048] S2, after the 3D-AAO / Al substrate was cleaned with deionized water, it was immersed in a 3 wt% phosphoric acid solution with a temperature of 50 DEG C for 60 min, the barrier layer was further thinned, and after being cleaned with deionized water, a 3D-AAO / Al substrate with a hole was obtained;

[0049] S3, a two-electrode electrolytic cell was used, the 3D-AAO / Al substrate with a hole was used as a cathode (the Al substrate was used as a current collector), a high-purity Ni sheet was used as an anode, a deionized water solvent was used for electrodeposition, 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 were contained, and a sulfuric acid solution was added dropwise to adjust the pH to 2.3. At a current density of 3 mA cm -2 , electrodeposition was performed for 3 h, and after the electrodeposition was completed, the 3D-AAO / Al substrate with a hole was taken out and immersed in a 1 M NaOH solution to selectively etch away the remaining Al substrate and the 3D hole AAO layer, thereby obtaining a nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interlinked mesh film, which is denoted as 3DNiFeCo MEA NW-3 h film.

[0050] Comparative Example 1

[0051] This comparative example provides a preparation method of a single metal nanowire three-dimensional interconnected mesh film. The specific steps refer to Example 1, and the only difference is that the electrodeposition solution in step S3 is deionized water as a solvent, containing NiSO4(0.12 M), NiCl2(0.12 M), H3BO3(0.5 M) and ascorbic acid (0.1 mg / mL), and a small amount of sulfuric acid solution is added to adjust the pH to 2.3. Finally, a nickel nanowire three-dimensional interconnected mesh film is prepared, denoted as 3D Ni NW film.

[0052] Comparative Example 2

[0053] This comparative example provides a preparation method of a double metal nanowire three-dimensional interconnected mesh film. The specific steps refer to Example 1, and the only difference is that the electrodeposition solution in step S3 is deionized water as a solvent, containing NiSO4(0.12 M), NiCl2(0.12 M), CoSO4(0.04 M), H3BO3(0.5 M) and ascorbic acid (0.1 mg / mL), 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, denoted as 3D NiCo NW film.

[0054] Comparative Example 3

[0055] This comparative example provides a preparation method of a double metal nanowire three-dimensional interconnected mesh film. The specific steps refer to Example 1, and the only difference is that the electrodeposition solution in step S3 is deionized water as a solvent, containing NiSO4(0.12 M), NiCl2(0.12 M), FeSO4(0.04 M), H3BO3(0.5 M) and ascorbic acid (0.1 mg / mL), and a small amount of sulfuric acid solution is added to adjust the pH to 2.3. Finally, a nickel-iron alloy nanowire three-dimensional interconnected mesh film is prepared, denoted as 3D NiFe NW film.

[0056] Performance test:

[0057] 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 test was carried out by using 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 -1Electrochemical impedance spectroscopy (EIS) was performed at frequencies ranging from 100 kHz to 0.01 Hz with an amplitude of 5 mV. Cyclic voltammetry (CV) was performed in the non-Radida region (0.926–1.026 V vs. RHE) with a scan rate ranging from 20 to 100 mV s. -1 To obtain the electrochemical double-layer capacitance (C2) of the catalyst. dl ).

[0058] (1) Morphology and structural characterization of electrodes

[0059] Figure 1 The flowchart illustrates the synthesis process of the 3D NiFeCo MEA NW structured integrated electrode of this invention. First, the 3D AAO template is enlarged. Then, a NiFeCo medium-entropy alloy nanowire mesh with a three-dimensional interconnected structure is prepared via a one-step co-electrodeposition method. This method is not only simple and mild, but also enables large-area controllable fabrication of the integrated electrode.

[0060] Figure 2 The image shows the structural characterization of the 3D NiFeCo MEA NW-1.5 h prepared in Example 1; (a) is an optical image confirming that the preparation method of this application can achieve large-area controllable preparation of integrated electrodes. Scanning electron microscopy (SEM) images show that the prepared 3D NiFeCo MEA NW-1.5 h has a thickness of approximately 15 μm, with uniformly grown vertical nanowires of approximately 200 nm in diameter, connected by transverse nanowires, and contains a large number of pores. Figure 2 (b) and Figure 2 (c) Transmission electron microscopy (TEM) images more clearly show the structure of vertical nanowires interconnected with horizontal 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) crystal plane of the FCC crystal structure. TEM images and XRD results indicate that 3D NiFeCoMEA NW-1.5 h possesses a highly crystalline FCC structure. Furthermore, energy-dispersive spectroscopy (EDS) images ( Figure 2 (f) shows that Ni, Fe, and Co elements are uniformly distributed, further confirming the successful preparation of 3D NiFeCo MEA NW-1.5 h. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to determine the final Ni:Fe:Co composition ratio as 30.8:38.8:30.4, with a mixing entropy ΔS. mix =1.092 R>R, which conforms to the medium entropy characteristic.

[0061] Figure 3 The compositional characterization of the 3D NiFeCo MEA NW-1.5 h prepared in Example 1 is shown; where (a) is the XRD structural characterization of nanowire mesh films 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 positions are slightly shifted to the left because adding 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 peaks at 800 cm⁻¹. -1 A broad peak was observed, possibly due to the presence of some oxides on the surface. To further explore the surface chemical bonding state of the sample, X-ray photoelectron spectroscopy (XPS) characterization was performed. The Ni2p 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 The presence of Ni is indicated by two spin-orbit pairs and two satellite peaks (abbreviated as "sat.") at a voltage of 873.6 eV. 2+ The secondary peaks at 852.1 eV and 869.2 eV are attributed to metallic Ni. Similarly, the deconvolution peaks at 710.8 eV and 723.9 eV, as well as the two satellite peaks in the Fe 2p distribution plot, 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 Ni content in the sample, the broad peak around 712.5 eV can be attributed to the Auger peak of the Ni LMM (Left-Milled Matrix). Figure 3 (d)). Meanwhile, Co 2p 3 / 2 peak and 2p 1 / 2 The peaks are at 781.1 eV and 796.8 eV, respectively, and Co 3+ The binding energies of the components are consistent, and the peaks at 777.8 eV and 792.9 eV are attributed to the metal Co (…). Figure 3 (e)). The O 1s spectrum can be decomposed into three distinct peaks ( Figure 3 (f) indicates that three characteristic peaks are observed at 529.6 eV, 531.4 eV, and 532.6 eV, labeled as MO, M-OH, and absorbed H2O, respectively. Therefore, the XPS test results reveal the metallic bonding properties of 3D NiFeCo MEA NW-1.5 h and the expected surface oxidation.

[0062] (2) Oxygen evolution reaction performance

[0063] The OER performance of the Ni Foam, 3D Ni NW, 3D NiFe NW, 3D NiCo NW, 3D NiFeCo MEA NW-1.5 h and commercial IrO2 catalyst (20wt%) was investigated using a typical three-electrode test system with 1.0 M KOH solution as the electrolyte. Linear sweep voltammetry (LSV) curves (Fig. 2) Figure 4 (a) show 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 overpotentials of the 3D NiFeCo MEA NW-1.5 h at 10, 100 and 500 mA cm -2 -2 were 218.6, 260.6 and 307.8 mV, respectively, which are significantly better than those of other catalysts (Fig. 2) Figure 4 (b), which reflects its 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 unique multi-element synergistic "cocktail effect" of 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 overpotentials of the 3D NiFeCo MEA NW-1 h at 10, 100 and 500 mA cm -2 -2 were 239.9, 279.8 and 326.1 mV, respectively; and the overpotentials of the 3D NiFeCo MEA NW-3 h at 10, 100 and 500 mA cm -2 -2 were 231.3, 274.7 and 329.7 mV, respectively, which all reflect its excellent electrocatalytic activity.

[0064] Figure 4 (c) shows the Tafel slopes corresponding to the polarization curves, which further understand 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, in the high current density region, 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 the IrO2 (138.1 mV dec -1This indicates that the material can maintain a rapid reaction kinetic process and has high mass transfer efficiency even at high current densities. Figure 4 The EIS results shown in (d) also validate this result, where the 3D NiFeCoMEA NW-1.5 h exhibits the smallest Nyquist radius and charge transfer resistance (R0). ct This confirms its excellent electronic conductivity and efficient charge transfer kinetics. Furthermore, based on double-layer capacitance (C... dl Estimated electrochemical active surface area (ECSA) analysis showed that ( Figure 4 (e)), 3D NiFeCo MEA NW-1.5 h C dl It is 12.87 mF cm -2 Higher than 3D NiNW (10.14 mF cm⁻¹). -2 ), IrO2 / NF (6.07 mF cm) -2 ) and pure nickel foam (3.28 mF cm) -2 This is thanks to its three-dimensional interconnected mesh structure, which effectively exposes abundant active sites. A systematic comparison with advanced OER catalysts in the prior art (…) Figure 4 (f)), 3D NiFeCo MEA NW-1.5 h at Tafel slope and 10 mA cm -2 The overpotential at various current densities showed significant advantages. Furthermore, stability is a key criterion for evaluating electrocatalysts, such as… Figure 4 As shown in (g), this application evaluates the stability of the prepared sample by constant current testing, requiring only a 1.56 V (vs. RHE) potential to drive a 500 mA cm⁻¹. -2 The catalyst exhibits high current density and remains stable even after 400 hours of continuous operation with negligible performance degradation, demonstrating excellent long-term stability even at high current densities. Based on the above analysis and existing OER catalysts, it is evident that the 3D NiFeCo MEA NW-1.5 h catalyst prepared in this application possesses superior OER catalytic activity and stability under alkaline conditions.

[0065] (3) The intrinsic mechanism of oxygen evolution reaction

[0066] To delve into the underlying reasons for the superior OER performance of the 3D NiFeCo MEA NW-1.5 h catalyst, this application characterizes the samples after OER stability testing. TEM images ( Figure 5 (a) This demonstrates that the three-dimensional nanowire structure of the material is completely preserved under harsh reaction conditions, and an ultrathin reconstructed layer forms on the surface. To further confirm the structure of the reconstructed layer, this application utilizes HRTEM ( Figure 5(b) Characterization of the reacted 3D NiFeCo MEA NW-1.5 h showed that the 0.204 nm lattice fringes of the nanowire core corresponded to the (111) crystal plane of the NiFeCo medium-entropy alloy, while an ultrathin (2-5 nm) reconstructed layer with a lattice fringes spacing of 0.208 nm, belonging to the highly active Ni(FeCo)OOH phase, was observed on the surface. No hydroxide was observed deep within the nanowire, further confirming that the reconstruction was uniformly covered only on the surface of the nanowire. XRD pattern ( Figure 5 (c) shows that the crystal structure is stable before and after the reaction without phase transition, which is consistent with the results of HRTEM observation 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 from the XPS test results before the stability test. The surface metallic Ni / Fe / Co signal completely disappeared and transformed into a high valence state. After argon ion etching, the core metallic characteristics gradually appeared. Figure 5 (d), (e), (f)). Correspondingly, in the O 1s spectrum ( Figure 5 (g) The peak intensity decreases with increasing etching depth. Depth profiling results show that oxidized Ni, Fe, and Co, as well as hydroxide groups, exist on the nanowire surface, while metallic Ni, Fe, and Co are present in the core. It can be considered that the core of the medium-entropy alloy nanowire has a highly crystalline metallic phase, which is a good electronic conductor; the hydroxyl oxides on the surface of the medium-entropy alloy nanowire are beneficial for promoting… The binding and catalytic activity of OH groups, along with the ultrathin thickness of the reconstructed layer, ensured efficient electron transfer from the surface to the core. In-situ Raman spectroscopy was used to further investigate the evolution of OER reactive 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 is an unreconstructed metallic state. When the potential is increased to 1.35 V, two new peaks appear: one at 476 cm⁻¹. -1 δ(Ni 3+ -O) bending vibration peak and 552 cm -1 ν(Ni 3+ -O) stretching vibration peaks, respectively corresponding to the E of NiOOH g Bending vibration and A 1gStretching vibration mode. When the potential rises to 1.65 V, the two main peaks are right-shifted, which means that the partial structure reorganization of Fe / Co sites is accompanied by the OER reaction process. In summary, the essence of the high performance of OER is ultimately determined to be the formation of the core-shell structure of the NiFeCo entropy alloy-Ni(FeCo)OOH ultra-thin ordered heterojunction. Ni(FeCo)OOH uniformly covers the nanowire surface to form a "passivation protection" under alkaline conditions, thereby protecting the 3D NiFeCo MEA NW-1.5 h from further corrosion in the alkaline and oxidative environment, and improving the mechanical and electrochemical stability. The lateral size of the hydroxide oxide of the restructured layer is small, and the thickness is ultra-thin, which can well 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 limited reconstruction strategy provides a new paradigm for designing efficient and stable OER catalysts.

[0067] (4) Performance of anion exchange membrane water electrolysis (AEMWE) devices

[0068] 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 as the diffusion layer), and a Pt-coated carbon paper (Pt loading 1 mg cm -2 , Pt / CP) was used as the cathode to assemble an AEMWE device ( Figure 6 (a)). The control group used an Ir-coated titanium felt (Ir loading 2 mg cm -2 , Ir / TF) as the anode and a Pt / CP as the cathode. The polarization curve was tested at 1.0 M KOH solution on the anode side at 60°C. The results show that the NiFeCo MEA NW / TF || Pt / CP electrolytic cell only needs 1.60 and 1.68 V voltage to achieve high current densities of 500 mA cm -2 and 1000 mA cm -2 (uncompensated by iR), which is significantly better than the 1.81 V required by the Ir / TF || Pt / CP to achieve 500 mA cm -2 ( Figure 6 (b)). More importantly, the electrolytic cell based on the NiFeCo MEA NW-1.5 h still shows excellent stability after running at a large current density of 1000 mA cm -2 for more than 160 hours ( Figure 6 (c)). This result proves that the 3D NiFeCo MEA NW-1.5 h electrode has high efficient and stable catalytic ability under harsh conditions, and shows good prospects for industrial applications.

[0069] ​Compared with the prior art, the preparation method and application of the three-dimensional ordered NiFeCo medium-entropy alloy grid thin film electrode have the following technical advantages:

[0070] 1. The transition metal-based medium-entropy alloy electrode adopts the method of template limited induction electrodeposition, constructs the three-dimensional grid thin film composed of NiFeCo medium-entropy alloy nanowires connected with each other, not only constructs the efficient electron transmission network for the catalytic electrode, improves the mass transfer efficiency, provides the rich active sites, but also increases the mechanical strength of the whole electrode, so that the catalyst has high stability.

[0071] 2. The application solves the problem of complicated preparation method of the medium-entropy alloy electrode, realizes the low-cost, green and large-batch preparation of the AEMWE anode electrode. The prepared electrode has high catalytic activity and excellent stability, and is expected to accelerate the commercialization process of the anion exchange membrane water electrolysis hydrogen production technology.

[0072] 3. The new electrode material successfully developed by the application shows excellent oxygen evolution reaction (OER) activity beyond the commercial IrO2, provides a new method for designing low-cost and high-stability non-noble metal catalyst system. In addition, the unique three-dimensional ordered structure and the synergistic optimization mechanism of the electrode can open up new ideas for the research and development of the new generation of flexible zinc-air batteries, supercapacitors and other clean energy devices.

[0073] Those skilled in the art should understand that the above description is only some specific embodiments of the application, not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications and 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 mesh film of nickel-iron-cobalt medium-entropy alloy nanowires, characterized in that, Includes the following steps: S1. A commercially available Al sheet containing Cu impurities is cut and then anodized to grow a 3D porous AAO layer on the Al sheet. When the growth is about to end, the anodizing voltage is gradually reduced by a continuous voltage reduction method to obtain a 3D-AAO / Al substrate. S2. Immerse the 3D-AAO / Al substrate in a phosphoric acid solution to obtain a pore-enlarged 3D-AAO / Al substrate; S3. The pore-expanded 3D-AAO / Al substrate is placed in an electrodeposition solution containing nickel salt, iron salt and cobalt salt for electrodeposition. The deposited alloy nanowires contain three metals in near-equal atomic ratio. The Al substrate and the 3D pore-expanded AAO layer are removed to obtain a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires, denoted as 3D NiFeCo MEA NW film.

2. The method for preparing a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1, characterized in that, In step S1, the thickness of the commercially available Al sheet containing Cu impurities is 0.1~0.2 mm, and the cut size is (5~10). (5~10)cm 2 .

3. The method for preparing a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1, characterized in that, In step S1, anodizing is performed using a 0.2-0.5 M H3PO4 mixed solution as the electrolyte. The electrolyte is composed of ethanol and deionized water in a volume ratio of 1:

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

4. The method for preparing a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1 or 3, characterized in that, In step S1, the anodizing voltage is gradually reduced using a continuous voltage reduction method, with each reduction being 2-5 V until the current density drops to 0-3 mA cm⁻¹. -2 Anodizing is stopped when the voltage drops to 50-55 V.

5. The method for preparing a three-dimensional interconnected mesh film of nickel-iron-cobalt medium-entropy alloy nanowires according to claim 1, characterized in that, 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℃ and a concentration of 3~10 wt% for 40~60 min.

6. The method for preparing a three-dimensional interconnected mesh 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. A 3D-AAO / Al substrate with expanded porosity is used as the cathode, an Al substrate as the current collector, and a high-purity Ni sheet as the anode. A solution containing nickel, iron, and cobalt salts is used as the electrodeposition solution, and the electrodeposition temperature is 3–8 mA cm⁻¹. -2 Deposition was carried out at a current density of 1-3 h.

7. The method for preparing a three-dimensional interconnected mesh 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 and 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 to 0.2 mg / mL ascorbic acid, with the pH adjusted to 2.0 to 3.

0.

8. The method for preparing a three-dimensional interconnected mesh 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 nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected mesh film prepared by the method of any one of claims 1-8.

10. The application of the nickel-iron-cobalt medium-entropy alloy nanowire three-dimensional interconnected mesh film of claim 9 as a self-supporting integrated alkaline oxygen evolution reaction electrode in industrial water electrolysis for hydrogen production.

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