Self-activated high entropy alloy OER catalytic electrode and preparation method thereof and alkaline OER application

Abstract

The present invention belongs to the field of alkaline water electrolysis hydrogen production, and specifically relates to a self-activated high entropy alloy OER catalytic electrode and its preparation method and alkaline OER application. The composition of the high entropy alloy is A x B y , A is composed of at least two elements of Fe, Co, Cr, Ni, and B is W, Mo or a combination thereof. Among them, the preferred high entropy alloy is FeCoCrNi. x W y It has a eutectic structure. Based on the mixing enthalpy characteristics of eutectic high-entropy alloys, the eutectic structure can be controlled through alloying and physical metallurgical means. Secondly, this eutectic high-entropy alloy can be directly used as an alkaline OER catalytic electrode without any treatment. During the OER process under high current density conditions in an alkaline environment, it will spontaneously activate and self-reconstruct to form a porous structure, greatly increasing the specific surface area of ​​the material, improving the mass transfer and gas diffusion processes, and enhancing the catalytic performance of the material.

Description

Technical Field

[0001] The present invention relates to the application field of alkaline water electrolysis catalysts, and specifically to a self-activated high-entropy alloy oxygen evolution reaction (OER) catalytic electrode and a preparation method thereof, and applies the same to alkaline water electrolysis hydrogen production. Background Art

[0002] Hydrogen production from water electrolysis primarily involves two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The OER, a four-electron transfer process with sluggish kinetics, is the key step that limits the overall reaction rate. To improve water electrolysis efficiency, the most effective strategy currently recognized is to develop low-cost, highly active OER catalysts.

[0003] Among the various reported water electrolysis catalysts, platinum group noble metals still hold the best overall performance. However, the high cost and limited reserves of noble metals severely limit their practical application. In recent years, non-noble metal catalysts based on transition metals such as Fe, Co, and Ni, and their compounds, have garnered widespread attention due to their low cost and impressive activity. Because these catalysts contain vacant d orbitals and unpaired d electrons, reactants can form various specialized chemical adsorption bonds on these vacant d orbitals, activating the molecules and thus reducing the reaction activation energy.

[0004] From a physical metallurgical perspective, alloying is the most effective method for manipulating a material's electronic and microstructural structure. It can produce at least two electronic effects that influence the material's surface activity: lattice strain and surface ligand effects. The phase composition and microstructure of multi-principal component high-entropy alloys play a crucial role in their performance. Eutectic high-entropy alloys, in particular, have lower melting points than pure principal components, exhibit better fluidity, simplify melting and casting operations, and offer a wide range of controllable methods for improving material properties.

[0005] Given that existing water electrolysis catalyst materials are prone to problems such as activity decay, structural collapse and limited mass transfer under high current density, and most of the preparation processes are complex or require subsequent processing, there is an urgent need for a catalytic material with low preparation cost that can be used directly as an anode without additional post-processing to adapt to the reaction environment of high current density of water electrolysis and meet the application requirements of long-term, efficient and stable service of alkaline water electrolysis hydrogen production under industrial high current density conditions. Summary of the Invention

[0006] The purpose of the present invention is to obtain a self-activated high-entropy alloy through physical metallurgical process control. The high-entropy alloy can be directly used as a catalytic electrode. While having low preparation cost, it does not require any additional processing, can adapt to the reaction environment of high current density of water electrolysis, and meet the application requirements of long-term, efficient and stable service of alkaline water electrolysis hydrogen production under industrial high current density conditions.

[0007] In a first aspect, the present invention provides a catalytic electrode, wherein the catalytic electrode is composed of a high entropy alloy composed of a 3d transition group non-noble metal component A and a negative mixing enthalpy component B; the composition expression of the high entropy alloy is A x B y , wherein A is composed of at least two elements selected from Fe, Co, Cr, and Ni, and B is W, Mo, or a combination thereof; x and y are atomic percentages of the elements, satisfying 75≤x≤100, 0≤y≤25, and x+y=100.

[0008] According to a preferred embodiment of the first aspect, A is composed of Fe, Co, Cr, and Ni, B is W, and the composition expression of the high entropy alloy is (FeCoCrNi) x W y .

[0009] According to a preferred embodiment of the first aspect, the high entropy alloy has a μ-FCC dual-phase structure, wherein the μ phase is enriched in W and Cr, and the FCC phase is enriched in Fe, Co and Ni.

[0010] According to a preferred embodiment of the first aspect, the high entropy alloy has a multi-scale eutectic structure formed by adjusting the W content, and the multi-scale eutectic structure has a phase transition process from FCC phase to composite eutectic microstructure phase and from the composite eutectic microstructure phase to μ phase.

[0011] According to a preferred embodiment of the first aspect, the high entropy alloy, after being subjected to constant current activation treatment as an alkaline OER anode, self-reconstructs to form a porous structure with a pore size of 400-600 nm.

[0012] In a second aspect, the present invention provides a use of the catalytic electrode according to any one of the second aspects in alkaline OER.

[0013] In a third aspect, the present invention provides a method for preparing a catalytic electrode, comprising the following steps: (a) preparing the raw materials according to the composition of the high entropy alloy, wherein the composition expression of the high entropy alloy is A x B y, A is composed of at least two elements of Fe, Co, Cr, and Ni, and B is W, Mo, or a combination thereof; x and y are atomic percentages of the elements, satisfying 75≤x≤100, 0≤y≤25, and x+y=100; (b) smelting and negative pressure suction casting: smelting the raw materials obtained in step (a) in a non-consumable vacuum arc furnace to obtain a molten alloy with uniform composition; injecting the molten alloy into a water-cooled copper mold by a negative pressure suction casting process to cool and solidify to form a high entropy alloy precursor; (c) annealing: annealing the precursor obtained in step (b) to achieve tissue homogenization control; (d) self-activation: the precursor treated in step (c) is used as an alkaline OER anode for constant current activation treatment, and self-reconstruction to form a catalytic electrode with a porous structure.

[0014] According to a preferred embodiment of the third aspect, in step (b), the smelting current is ≥200 A, and the smelting temperature is ≥3000°C.

[0015] According to a preferred embodiment of the third aspect, in step (c), the annealing temperature is 1000-1500° C., and the holding time is 4-8 h.

[0016] According to a preferred embodiment of the third aspect, step (d) comprises: treating the precursor as an anode in a 1M KOH solution at room temperature at 1A cm -2 A constant current activation treatment is performed for more than 100 h at a current density, and then the catalytic electrode is washed with ultrapure water and anhydrous ethanol in sequence and dried to obtain the catalytic electrode.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The self-activated OER catalyst can be integrally formed through physical metallurgical technology. More importantly, the catalyst does not require any additional treatment and can be directly used as an alkaline OER catalytic electrode. In addition, it will spontaneously activate during the OER process and self-reconstruct to form a porous structure. The preparation process is simple and fast, and it can be prepared in large quantities, which is easy to industrialize and saves processing costs.

[0019] (2) The catalytic electrode has a stable, self-supporting three-dimensional porous structure, which can maintain the stability of active sites and its own structure during long-term stability tests. It can overcome the problem of traditional nanoparticle catalysts in which active sites are easily detached during long-term stability, resulting in decreased activity and insufficient stability, and achieve stable service under high current density, which has good prospects for industrial application.

[0020] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention and to enable one skilled in the relevant art to make and use the invention.

[0022] Figure 1 The FeCoNiCrW prepared in Example 1 0.6 X-ray diffraction (XRD) patterns of the precursors.

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the precursor prepared in Example 1, wherein (a) is FeCoNiCrW 0.4 , (b) is FeCoNiCrW 0.55 , (c) is FeCoNiCrW 0.6 , (d) is FeCoNiCrW 0.7 , (e) is FeCoNiCrW 0.8 .

[0024] Figure 3 It is the FeCoNiCrW prepared in Example 2 0.6 XRD pattern of the catalytic electrode.

[0025] Figure 4 It is the FeCoNiCrW prepared in Example 2 0.6 SEM image of the catalytic electrode.

[0026] Figure 5 The FeCoNiCrW prepared in Comparative Example 1 0.7 XRD pattern of the catalytic electrode.

[0027] Figure 6 The FeCoNiCrW prepared in Comparative Example 1 0.7 SEM image of the catalytic electrode.

[0028] Figure 7 It is the FeCoNiCrW prepared in Example 2 0.6 The catalytic electrode and the FeCoNiCrW prepared in Example 1 0.6 Comparison of linear voltammetric scan curves of the precursors in 1 M KOH electrolyte.

[0029] Figure 8 The FeCoNiCrW prepared in Comparative Example 1 0.7 The catalytic electrode and the FeCoNiCrW prepared in Example 1 0.7 Comparative linear sweep voltammetry curves of the precursors in 1 M KOH electrolyte.

[0030] Figure 9 The FeCoNiCrW prepared in Comparative Example 1 0.7 The catalytic electrode and the FeCoNiCrW obtained by self-activation in Example 2 0.6 Comparison of Tafel slope curves of catalytic electrodes in 1 M KOH electrolyte.

[0031] Figure 10 It is the FeCoNiCrW prepared in Example 2 0.6 The catalytic electrode is at 1A cm -2 Voltage-time curve under current density conditions. DETAILED DESCRIPTION

[0032] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments may be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, the description of these embodiments is intended to make the present disclosure more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a deeper understanding of the embodiments of the present invention.

[0033] (Composition design of catalytic electrode)

[0034] An embodiment of the present invention relates to a catalytic electrode, which is an alloy, specifically a high-entropy alloy. The high-entropy alloy is designed to be composed of a 3d transition metal non-noble metal component A and a negative mixing enthalpy component B, wherein component A can provide abundant active sites for OER due to its spare d orbitals and unpaired d electrons; component B has a significant negative mixing enthalpy with the transition metal and can be enriched in the eutectic or second phase to form a local reinforced structure and contribute to a porous structure during electrochemical reconstruction. The design concept of this high-entropy alloy is to optimize the surface activity and structural stability of the electrode through the synergistic effect of multiple transition metal elements and the strengthening effect of the negative mixing enthalpy element.

[0035] In terms of component ratio, A x B y represents the overall composition of the high-entropy alloy, wherein A is composed of at least two elements of Fe, Co, Cr, and Ni, and B is W, Mo, or a combination thereof, wherein x and y are the atomic percentages of the elements, satisfying 75≤x≤100, 0≤y≤25, and x+y=100.

[0036] As a further preferred component ratio, A is composed of Fe, Co, Cr, and Ni, and B is W. The composition expression of the high entropy alloy is (FeCoCrNi) x W y .

[0037] This high-entropy alloy is composed of two phases, exhibiting a typical μ-FCC dual-phase structure: the μ phase is enriched in W and Cr, and the FCC phase is enriched in Fe, Co, and Ni. The W- and Cr-rich μ phase is distributed in the matrix, with a compact lattice structure and high hardness, providing a microscopic template for the formation of a porous structure during electrochemical self-activation. Meanwhile, the Fe-, Co-, and Ni-rich FCC phase imparts excellent electrical conductivity and sufficient ductility to the high-entropy alloy. The synergistic coexistence of the two phases not only ensures the alloy's durability but also provides abundant interfacial active sites for the oxygen evolution reaction.

[0038] This high-entropy alloy exhibits a multiscale eutectic structure. This multiscale eutectic structure is achieved by adjusting the W content to transform the high-entropy alloy from an FCC phase to a composite eutectic phase to a μ phase. When the W content is low, the alloy is primarily composed of an FCC phase rich in Fe, Co, and Ni. As the W content increases, the eutectic phase begins to precipitate at grain boundaries or within grains to form a secondary phase. As the W content increases further, the W- and Cr-rich μ phase becomes the predominant secondary phase.

[0039] (Preparation of Catalytic Electrode)

[0040] In general, the catalytic electrodes involved in the embodiments of the present invention are obtained through physical metallurgical process control. Physical metallurgical process control mainly involves steps such as alloy smelting, solidification, and heat treatment to adjust parameters such as the alloy's microstructure, thereby achieving control over the morphology of the high-entropy alloy precursor and ultimately self-reconstructing to form a porous catalytic electrode under alkaline water electrolysis conditions.

[0041] The steps for preparing the catalytic electrode involved in the embodiment of the present invention are as follows:

[0042] (a) Ingredients

[0043] The raw materials are configured according to the specific composition required by the high entropy alloy, and the purity of the raw materials is ensured to reach or exceed 99.5 wt%. The composition expression of the high entropy alloy is A x B y , A is composed of at least two elements selected from Fe, Co, Cr, and Ni, and B is W, Mo, or a combination thereof; x and y are atomic percentages of the elements, satisfying 75≤x≤100, 0≤y≤25, and x+y=100.

[0044] (b) Melting and vacuum casting

[0045] The raw materials obtained in step (a) are melted in a non-consumable vacuum arc furnace to obtain a molten alloy with uniform composition, and then the molten alloy is poured into a water-cooled copper mold by a negative pressure suction casting process to cool and solidify to form a high entropy alloy precursor.

[0046] Specifically, under the protection of high-purity Ar atmosphere, the ingredients in step (a) are smelted in a non-consumable vacuum arc furnace. The smelting current is set to not less than 200A, the smelting temperature is set to not less than 3000°C, and the smelting is repeated for not less than 5 times to ensure that each element is fully and evenly diffused in the master alloy ingot to obtain a molten alloy with uniform composition. Then, the molten alloy is infiltrated into a water-cooled copper mold by a negative pressure suction casting method. Under the action of negative pressure, the molten alloy quickly fills the cavity of the copper mold and is rapidly cooled in the copper mold. During the cooling process, the alloy melt gradually solidifies to obtain a high-entropy alloy precursor in the form of a rod or plate.

[0047] (c) Annealing

[0048] The precursor obtained in step (b) is annealed to achieve tissue homogenization control.

[0049] Specifically, the precursor obtained in step (b) is annealed in a high-temperature furnace at 1000-1500°C for 4-8 hours. This annealing treatment homogenizes the precursor structure, thereby reducing hardness and improving machinability; lowering residual stress, stabilizing dimensions, and reducing deformation and cracking tendencies; and simultaneously refining grains, adjusting the microstructure, and eliminating microstructure defects. This further homogenizes the material structure and composition, improving the overall performance and service life of the alloy.

[0050] (d) Self-activation (alkaline OER applications)

[0051] The precursor treated in step (c) is used as an alkaline OER anode for constant current activation treatment (constant current stability test) to self-reconstruct into a catalytic electrode with a porous structure.

[0052] Specifically, after annealing, the precursor was directly used as the anode for water electrolysis at room temperature, immersed in 1 M KOH electrolyte, and applied 1 A cm -2 Constant current was applied for more than 100 hours to simulate the high-load operating environment of the OER. During this process, the W- and Cr-rich μ-phase on the alloy surface preferentially dissolved, leaving behind the FCC phase structure. After activation, the catalytic electrode was rinsed multiple times with ultrapure water and anhydrous ethanol to remove residual dissolved products in the pores, and finally dried in an oven to constant weight. While maintaining the integrity of the overall morphology, the resulting catalytic electrode also has a nanoscale porous structure with pore sizes of 400-600 nm, significantly improving the specific surface area, electrolyte permeability, and OER activity.

[0053] In addition, in order to better illustrate the advantages of the self-activation process of the present invention, as a comparison, the Fe, Co, and Ni-rich FCC phase can also be removed by dealloying to prepare a porous high-entropy alloy. As a replacement for step (d), the dealloying process is to place the precursor prepared by steps (a)-(c) in an acidic solution for electrochemical dealloying treatment. The process conditions are, for example, room temperature, 0.5 mol L -1 H2SO4 solution, apply 1-2V corrosion potential for 0.5-2h.

[0054] In order to better understand the present invention, the present invention is further described below based on detailed examples, but the present invention is not limited to these examples.

[0055] It should be noted that the FeCoNiCrW prepared in the following examples 0.4 、FeCoNiCrW 0.55 、FeCoNiCrW 0.6 、FeCoNiCrW 0.7 、FeCoNiCrW 0.8 In the high entropy alloy, the atomic percentages of Fe, Co, Ni, and Cr are all 1:1:1:1, and the atomic percentages of W are 0.4, 0.55, 0.6, 0.7, and 0.8, respectively. The total mass of the ingredients in each embodiment is controlled at 20 g.

[0056] (Example 1)

[0057] According to the nominal composition of high entropy alloy FeCoNiCrW 0.4 、FeCoNiCrW 0.55 、FeCoNiCrW 0.6 、FeCoNiCrW 0.7 、FeCoNiCrW 0.8 The alloy raw materials (purity above 99.5 wt%) were prepared and weighed according to the atomic percentage of the alloy. The weighed raw materials were smelted in a copper crucible of a non-consumable vacuum arc furnace under the protection of high-purity Ar atmosphere. The smelting current was 200 A and the smelting time was 5 min. The smelting was repeated 8 times to ensure the uniform composition of the master alloy ingot. Then, FeCoNiCrW with a μ-FCC structure in the form of a plate was obtained by negative pressure suction casting. 0.4 、FeCoNiCrW 0.55 、FeCoNiCrW 0.6 、FeCoNiCrW 0.7 、FeCoNiCrW 0.8 Precursor.

[0058] Figure 1It is the FeCoNiCrW prepared in Example 1 of the present invention 0.6 X-ray diffraction (XRD) pattern of the precursor. The diffraction peaks can be divided into two groups: one corresponding to the Fe-, Co-, and Ni-rich FCC phase; the other corresponding to the W- and Cr-rich μ phase. It can be seen that when the W content reaches 0.6, the alloy evolves from a single FCC phase to a dual-phase structure of FCC + μ, in which the FCC phase is the primary phase and the μ phase coexists as a dispersed secondary phase.

[0059] Figure 2 This is a scanning electron microscope (SEM) image of the precursor prepared in Example 1 of the present invention, wherein (a) is FeCoNiCrW 0.4 , (b) is FeCoNiCrW 0.55 , (c) is FeCoNiCrW 0.6 , (d) is FeCoNiCrW 0.7 , (e) is FeCoNiCrW 0.8 It can be seen that when the W content is low (atomic percentage of 0.4), the alloy mainly presents a continuous FCC matrix; with the increase of W content (atomic percentage of 0.55), strip-shaped and plate-shaped second phase precipitates appear simultaneously in the matrix crystals and at the grain boundaries, indicating the initial formation of a composite eutectic structure; when the W content continues to increase (atomic percentage of 0.6), the number and size of the second phase increase significantly, showing densely distributed rod-shaped and fibrous eutectic strips, which coexist with the FCC matrix; further increase the W content (atomic percentage of 0.7), the W- and Cr-rich μ phase coarsens and aggregates in the dark matrix in the form of blocks and irregular islands, while the FCC phase is relatively discrete; with the further increase of W content (atomic percentage of 0.8), the μ phase further develops into a continuous strip / network structure, and the entire organization presents a highly developed multi-scale eutectic morphology. As shown, as the W content gradually increases, the precursor alloy undergoes a transformation from FCC phase to composite eutectic phase to μ phase, achieving the goal of precisely controlling the content and morphology of FCC and μ phases by adjusting the W element ratio. This result demonstrates that the precursor phase structure can be regulated by changing the alloy ratio.

[0060] (Example 2)

[0061] The FeCoNiCrW prepared in Example 1 0.6 The precursor was annealed at 1200 °C for 6 h to regulate and homogenize the crystal structure and organization of the alloy. 0.6 The precursor was placed in 1M KOH solution for electrochemical stability test, during which self-activation occurred.-2 After working for 300 hours under the same conditions, the FeCoNiCrW was washed with ultrapure water and anhydrous ethanol several times to remove the residual chemicals in the pores, and then dried to obtain a porous FeCoNiCrW 0.6 catalytic electrode.

[0062] Figure 3 It is the FeCoNiCrW prepared in Example 2 0.6 XRD pattern of the catalytic electrode. The XRD results show that the self-reconstruction process has essentially removed the W- and Cr-rich μ-phase on the surface. In other words, the surface μ-phase has been essentially reconstructed or removed during the self-activation process, leaving behind the FCC phase structure. Figure 4 It is the FeCoNiCrW prepared in Example 2 0.6 SEM image of the catalytic electrode. SEM results show that the W- and Cr-rich μ-phase on the surface has been removed, forming a porous structure. The porous high-entropy alloy has formed nanoscale pores with a size of 400-600 nm, forming a multi-scale porous structure with a high specific surface area. This provides a large number of exposed active sites and smooth ion transport channels for the water electrolysis process.

[0063] (Comparative Example 1)

[0064] The FeCoNiCrW prepared in Example 2 0.7 The precursor was annealed at 1200 °C for 6 h. 0.7 The precursor was placed in a 0.5M H2SO4 solution for electrochemical dealloying at 1.2V for 1 hour. After the corrosion was completed, it was also cleaned with ultrapure water and anhydrous ethanol and dried. That is, it was washed with ultrapure water and anhydrous ethanol multiple times in sequence to remove the residual chemicals in the pores. After drying, FeCoNiCrW with a porous structure was obtained. 0.7 catalytic electrode.

[0065] Figure 5 The FeCoNiCrW prepared in Comparative Example 1 0.7 XRD pattern of the catalytic electrode. XRD results show that the FCC phase diffraction peaks almost disappear after dealloying, leaving only the characteristic peaks of the W- and Cr-rich μ-phase, indicating that the solution corrosion process preferentially dissolves the Fe-, Co-, and Ni-rich FCC phase. Figure 6 The FeCoNiCrW prepared in Comparative Example 1 0.7 SEM image of the catalytic electrode. The results show the formation of a dendritic porous structure with a diameter of approximately 200-400 nm.

[0066] (Test Example 1)

[0067] The FeCoNiCrW prepared in Example 10.6 Precursor and FeCoNiCrW obtained by self-activation in Example 2 0.6 A three-electrode system was composed of a catalytic electrode as the working electrode, a platinum wire electrode as the auxiliary electrode, and a Hg / HgO standard electrode as the reference electrode. Linear voltammetric scans were performed in 1 M KOH solution at a scan rate of 50 mV / s.

[0068] Figure 7 It is the FeCoNiCrW prepared in Example 2 0.6 The catalytic electrode and the FeCoNiCrW prepared in Example 1 0.6 The linear voltammetric scanning comparison curve of the precursor in 1M KOH electrolyte. Through testing, it was found that the FeCoNiCrW obtained after self-activation 0.6 Catalytic electrode, at 10 mA cm -2 At this current density, the required overpotential was only 227 mV, while the precursor alloy without self-activation exhibited a significantly higher overpotential requirement. This significant difference indicates that the porous high-entropy alloy catalytic electrode activated by constant current achieves superior oxygen evolution reaction (OER) catalytic performance due to increased surface micropores and enhanced exposure of active sites.

[0069] (Test Example 2)

[0070] The FeCoNiCrW prepared in Example 1 0.7 Precursor and FeCoNiCrW prepared in Comparative Example 1 0.7 A three-electrode system was composed of a catalytic electrode as the working electrode, a platinum wire electrode as the auxiliary electrode, and a Hg / HgO standard electrode as the reference electrode. Linear voltammetric scans were performed in 1 M KOH solution at a scan rate of 50 mV / s.

[0071] Figure 8 The FeCoNiCrW prepared in Comparative Example 1 0.7 The catalytic electrode and the FeCoNiCrW prepared in Example 1 0.7 The linear sweep voltammetry comparison curve of the precursor in 1M KOH electrolyte. Through testing, it was found that the FeCoNiCrW obtained after selective dealloying 0.7 catalytic electrode capable of 10 mA cm -2 At the catalytic current density, the required overpotential is 280 mV, while the precursor is 10 mA cm -2At the catalytic current density, the required overpotential was 255 mV. This indicates that the electrocatalytic performance of the porous high-entropy alloy catalytic electrode is somewhat reduced compared to that of the precursor, demonstrating that the catalytic performance order from highest to lowest is: after self-activation > precursor > after dealloying. This result further confirms the significant advantages of the porous structure obtained by self-activation compared to the simple dealloying method in terms of active site exposure, electron / ion transport channels, and overall catalytic efficiency.

[0072] (Test Example 3)

[0073] The FeCoNiCrW obtained by self-activation in Example 2 was used respectively. 0.6 Catalytic electrode and FeCoNiCrW prepared in Comparative Example 1 0.7 A three-electrode system was composed of a catalytic electrode as the working electrode, a platinum wire electrode as the auxiliary electrode, and a Hg / HgO standard electrode as the reference electrode. Linear voltammetric scans were performed in 1 M KOH solution at a scan rate of 50 mV / s.

[0074] Figure 9 The FeCoNiCrW prepared in Comparative Example 1 0.7 The catalytic electrode and the FeCoNiCrW obtained by self-activation in Example 2 0.6 The Tafel slope comparison curve of the catalytic electrode in 1M KOH electrolyte. The results show that the self-activated FeCoNiCrW 0.6 The Tafel slope of the catalytic electrode is only 25.38 mV / dec, while the dealloyed FeCoNiCrW 0.7 The Tafel slope of the catalytic electrode is 32.94 mV / dec. A lower Tafel slope means a smaller overpotential increase required for a smaller current increment. The self-activated electrode exhibits a faster electrocatalytic kinetic response and a higher reaction rate constant, further demonstrating the significant advantage of the self-activated porous structure in improving the OER reaction kinetics.

[0075] (Test Example 4)

[0076] The FeCoNiCrW prepared in Example 1 was used 0.6 A high-entropy alloy was used as the working electrode, a platinum wire electrode was used as the auxiliary electrode, and a Hg / HgO standard electrode was used as the reference electrode to form a three-electrode system. Constant current testing was carried out in 1 M KOH solution.

[0077] Figure 10 It is the FeCoNiCrW prepared in Example 2 0.6 The catalytic electrode is at 1A cm -2 The voltage-time curve under current density conditions. The results show that the catalytic electrode can be used in 1M KOH solution at 1 A cm -The stable operation for more than 400 hours under the current density of 2000 ℃ and 10000 ℃ has proved that the FeCoNiCrW prepared by the present invention 0.6 The catalytic electrode has good oxygen evolution stability. It not only has excellent OER catalytic activity, but also can maintain excellent structural stability and electrochemical durability under high current density and long-term operation conditions, fully verifying the practical value and industrial application potential of the catalytic electrode of the present invention.

[0078] In summary, the present invention provides an OER catalytic electrode based on (Fe-Co-Cr-Ni)-W (and / or Mo) multi-principal element high entropy alloy and its preparation method. By accurately matching 3d non-precious metal components with negative mixing enthalpy components and combining physical metallurgical processes, the microstructure fine-tuning and electrochemical self-activation of the alloy precursor are achieved. The catalytic electrode can spontaneously reconstruct a uniformly distributed nano- to submicron-scale porous network structure under alkaline water electrolysis conditions, which greatly improves the specific surface area and interfacial active site exposure of the electrode; and the synergistic effect of the FCC phase and μ phase in the two-phase structure not only ensures excellent electron transport and mechanical stability, but also promotes the controllability of pore generation. Compared with the traditional dealloying preparation method, the self-activation strategy of the present invention can obtain better catalytic activity and long-term durability at high current density without acid corrosion. Experiments have shown that the prepared FeCoNiCrW 0.6 The catalytic electrode was at 10 mA cm -2 The overpotential is as low as 227mV at the current density, the Tafel slope is only 25.38mV / dec, and it can be used at 1A cm -2 The stable operation lasted for more than 400 hours, which fully demonstrated the outstanding advantages of the present invention in the efficient, stable and scalable preparation of non-precious metal OER catalysts and has broad prospects for industrial application.

[0079] In some embodiments, the high entropy alloy precursor of the present invention is used as an anode for alkaline OER reaction, driving 10 mA cm in 1 M KOH. -2 The overpotential required for the current density is 253-257 mV, and the Tafel slope is 32.94-34.51 mV dec -1 The overpotential of the catalytic electrode after activation reached 227-235 mV, and the Tafel slope was 25.38-26.89 mV dec. -1 , the overpotential decreased by more than 18 mV.

[0080] The remaining examples can be implemented similarly to the above examples, with the difference being that the nominal composition of the ingredients is varied to obtain different multi-scale eutectic structures. These materials can self-activate in an alkaline environment and under high current density conditions, exhibiting excellent alkaline OER performance.

[0081] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing what is disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as illustrative only, and the present invention is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and variations may be made without departing from the scope thereof.

Claims

1. A catalytic electrode, characterized in that: The catalytic electrode is composed of a high entropy alloy consisting of a 3d transition group non-noble metal component A and a negative mixing enthalpy component B; The composition expression of the high entropy alloy is A x B y , where A is composed of Fe, Co, Cr, and Ni in equal atomic percentages, and B is W; x and y are the atomic percentages of the elements, satisfying 12.08≤y≤16.67, and x+y=100; The high entropy alloy is melted in a non-consumable vacuum arc furnace and cast into a water-cooled copper mold by negative pressure suction to obtain a high entropy alloy precursor. After annealing at a temperature of 1000-1500 °C and a holding time of 4-8 h, the precursor is used as an alkaline OER anode in a 1 M KOH solution at a constant current of 1 A·cm -2 After activation for more than 100 h, the catalytic electrode self-reconstructs into a porous structure with a pore size of 400~600 nm.

2. The catalytic electrode according to claim 1, characterized in that The high entropy alloy has a μ-FCC dual-phase structure, wherein the μ phase is enriched in W and Cr, and the FCC phase is enriched in Fe, Co and Ni.

3. The catalytic electrode according to claim 2, characterized in that The high entropy alloy has a multi-scale eutectic structure formed by adjusting the W content, and the multi-scale eutectic structure has a phase transformation process of transforming from an FCC phase to a composite eutectic microstructure phase and from the composite eutectic microstructure phase to a μ phase.

4. Use of the catalytic electrode according to any one of claims 1 to 3 in alkaline OER.

5. A method for preparing a catalytic electrode, characterized in that: The following steps are involved: (a) Ingredients: The raw materials are prepared according to the composition of the high entropy alloy, wherein the composition expression of the high entropy alloy is A x B y , A is composed of Fe, Co, Cr, and Ni in equal atomic percentages, and B is W; x and y are the atomic percentages of the elements, satisfying 12.08≤y≤16.67, x+y=100; (b) Melting and Vacuum Casting: Melting the raw materials obtained in step (a) in a non-consumable vacuum arc furnace to obtain a molten alloy with uniform composition; pouring the molten alloy into a water-cooled copper mold using a vacuum casting process to cool and solidify it to form a high-entropy alloy precursor; (c) Annealing: The precursor obtained in step (b) is subjected to an annealing treatment at a temperature of 1000-1500°C and a holding time of 4-8 hours to achieve tissue homogenization; (d) Self-activation: The precursor treated in step (c) was used as an alkaline OER anode in 1 M KOH solution at 1 A cm -2 The catalytic electrode was self-reconstructed to form a porous structure with a pore size of 400-600 nm by constant current activation treatment at a current density of more than 100 h.

6. The preparation method according to claim 5, characterized in that In step (b), the smelting current is ≥200 A and the smelting temperature is ≥3000°C.

7. The preparation method according to claim 5, characterized in that Step (d) comprises: The precursor was used as an anode in 1 M KOH solution at room temperature and the reaction temperature was 1 A cm -2 A constant current activation treatment is performed for more than 100 h at a current density, and then the catalytic electrode is washed with ultrapure water and anhydrous ethanol in sequence and dried to obtain the catalytic electrode.

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