A self-supported porous high-entropy alloy electrocatalytic material for overall water splitting and its preparation method

Abstract

The present invention discloses a self-supporting porous high-entropy alloy overall water splitting catalytic material and a preparation method thereof. In terms of the molar percentage content of each atom, the chemical formula is (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100‑x Al x , where 50 ≤ x ≤ 67. The preparation method is as follows: First, weigh the raw materials of iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom, and perform arc melting to obtain a master alloy ingot; use the melt spinning quenching method to obtain a high-entropy alloy strip from the obtained master alloy ingot; perform alkali etching on the obtained high-entropy alloy strip, and after cleaning and drying, it is prepared. By increasing the content of Al element in the alloy and using the alkali etching method to obtain a nanoporous structure, the high-entropy alloy prepared by the present invention has the characteristics of multiple synergistic effects and chemical short-range order, and can be directly used as a self-supporting electrolytic water electrode. The preparation method is simple and easy to operate, overcoming the disadvantages of powder catalytic materials that require binders and have poor stability.

Description

Technical Field

[0001] The present invention relates to a catalyst material for overall water splitting and a preparation method thereof, and particularly to a self-supporting porous high-entropy alloy catalyst material for overall water splitting and a preparation method thereof. Background Art

[0002] The electrolysis of water has a simple process and no pollution in the production process, and is the most promising technical method for producing high-purity hydrogen. The electrolysis of water reaction includes a hydrogen evolution reaction (HER) at the cathode and an oxygen evolution reaction (OER) at the anode. At present, noble metal Pt / C catalysts are commonly used for the cathode reaction, and noble metal oxides IrO 2 , RuO 2 catalysts are commonly used for the anode reaction. Noble metal catalyst materials have excellent performance, but their high price, scarce reserves and complex processing and preparation methods are the bottlenecks restricting the development of electrolysis water technology. Therefore, the development of low-cost, highly efficient and stable electrolysis water catalyst materials is of great significance for promoting the development of the new energy field in China.

[0003] Transition metal elements such as iron, cobalt, and nickel have low prices and excellent catalytic activities, and have been widely reported in the field of electrolysis water catalyst materials. The unique high-entropy effect, lattice distortion effect, sluggish diffusion effect and "cocktail" effect of high-entropy alloys have potential advantages as electrolysis water catalyst materials. At the same time, in recent years, more and more studies have shown that due to the different atomic sizes of the constituent atoms of high-entropy alloys and the complex interactions between elements, a short-range ordered (or locally chemically ordered) structure is usually formed during solidification or heat treatment, which provides new ideas for regulating the local electronic structure and optimizing the catalytic reaction active sites, but there is no relevant report yet. In addition, among various forms of high-entropy alloy materials such as powders, bulk materials, and thin films, high-entropy alloy strips with low self-weight and directly usable as electrodes have innate advantages. However, the specific surface area of high-entropy alloy strips is small, and currently, constructing a surface nanoporous structure through natural etching or electrochemical dealloying is an effective way to increase the number of surface active sites and improve the catalytic activity.

[0004] Chinese patent application with publication number CN113782755A discloses a preparation method of a nanoporous bifunctional catalytic material. The atomic percentages of Al, Co, Fe, Mo, Cr, and Pt are 95.9:1:1:1:1:0.1. A powder catalytic material is obtained through arc melting, melt spinning, and dealloying, and is coated on carbon cloth as an electrode. This method requires a binder when loading the catalytic material, resulting in a reduction in the electron transfer efficiency between the substrate and the catalytic material, and the catalytic material is prone to falling off during a long-term reaction process. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a self-supporting porous high-entropy alloy catalyst material for overall water splitting with a large specific surface area of the active material and high cycle stability;

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned self-supporting porous high-entropy alloy overall water splitting catalytic material.

[0007] Technical solution: The self-supporting porous high-entropy alloy overall water splitting catalytic material of the present invention has a chemical formula of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100-x Al x , where 50 ≤ x ≤ 67.

[0008] The method for preparing the above-mentioned self-supporting porous high-entropy alloy overall water splitting catalytic material includes the following steps:

[0009] (1) Weigh the raw materials of iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom;

[0010] (2) Arc melt the above raw materials to obtain an (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100-x Al x master alloy ingot;

[0011] (3) Use the melt spinning quenching method on the obtained master alloy ingot to obtain an (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100-x Al x high-entropy alloy strip;

[0012] (4) Subject the obtained high-entropy alloy strip to alkaline etching, followed by washing and drying to obtain the self-supporting porous Al-based high-entropy alloy alkaline overall water splitting catalytic material.

[0013] Among them, in the step (2), argon is used as the protective atmosphere for arc melting, and remelting is performed at least 4 times to ensure uniform alloy composition.

[0014] Among them, in the step (3), the rotational speed of the copper roller is 700 - 1000 revolutions per minute. When the rotational speed is lower than 700 revolutions per minute, the strip thickness is larger and the self-weight is larger; the higher the rotational speed, the thinner the obtained strip thickness, which is beneficial to reducing the self-weight of the strip and obtaining higher mass activity; however, when the rotational speed is higher than 1000 revolutions per minute, the mechanical properties of the strip prepared from this composition are poor and it is prone to brittle fracture, making it inconvenient to be used as an electrode material.

[0015] Among them, in the step (3), argon is used as the protective atmosphere for the melt spinning quenching method.

[0016] Among them, in the step (4), the concentration of the alkali etching is 1-6M, the etching time is 0.5-12h, and the temperature is preferably room temperature. The higher the concentration of the etching medium, the shorter the corresponding etching time. Since the formation of the short-range order structure results from the atomic rearrangement during the etching process, if the etching time is too short, it is difficult to form a considerable number of short-range order structures. If the etching time is too long, more element leaching will cause the loss of active sites. When the concentration of the etching medium is lower than 1M, the required etching time is too long and the efficiency is low.

[0017] Among them, the medium for the alkali etching in the step (4) is a KOH solution. Since iron, cobalt, nickel, and copper are insoluble in alkaline solutions, using a KOH solution can selectively etch the aluminum element in the strip to form a porous structure and maximize the retention of the active sites of the transition metals.

[0018] Among them, in the step (4), the cleaning medium is water and absolute ethanol.

[0019] Principle of the invention: By selecting an appropriate aluminum element content and using a KOH solution for selective etching to obtain a porous structure, iron, cobalt, and nickel transition elements are selected as commonly used electrocatalytic active elements. During the etching process, as the aluminum element is continuously removed, the occupancy of the remaining elements rearranges. Due to the different mixing enthalpies of copper with iron, cobalt, nickel, and aluminum elements, there is a specific preference / rejection relationship for atomic occupancy, forming a specific short-range ordered structure. The interaction between different elements highlights the advantages of the multi-element synergistic effect of the high-entropy alloy, and realizes the regulation of the local electronic structure, reduces the reaction energy barrier of the active sites, and improves the catalytic performance of water electrolysis.

[0020] Beneficial effects: Compared with the prior art, the present invention has achieved the following remarkable effects: (1) By increasing the content of the Al element in the alloy and using an alkali etching method to obtain a nanoporous structure, the prepared high-entropy alloy has the characteristics of multi-element synergistic effect and chemical short-range order, and can be directly used as a self-supporting water electrolysis electrode. The preparation method is simple and easy to operate, overcoming the disadvantages of powder catalytic materials that require binders and have poor stability; (2) It has excellent catalytic performance for overall water splitting under alkaline conditions and low cost, which promotes the application of high-entropy alloy strips in water electrolysis catalysis. Description of the drawings

[0021] Figure 1 The X-ray diffraction pattern of the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip varying with the etching time;

[0022] Figure 2 The (Fe 0.25 Co0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Scanning electron microscope images of high-entropy alloy strips as a function of etching time;

[0023] Figure 3 For the original (Fe in Example 1 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Transmission electron microscope images of high-entropy alloy strips;

[0024] Figure 4 For the etched for 4 h (Fe in Example 1 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Transmission electron microscope images of high-entropy alloy strips;

[0025] Figure 5 For the etched for different times (Fe prepared in Example 1 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Linear sweep voltammetry curves of HER of high-entropy alloy strips in 1 M KOH electrolyte;

[0026] Figure 6 For the etched for 4 h (Fe in Example 1 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 When the high-entropy alloy strip is used as a catalytic material for HER in electrolytic water, at 20 mA / cm in 1 M KOH electrolyte 2 and 50 mA / cm 2 Chronoamperometry curves;

[0027] Figure 7 For the etched for different times (Fe prepared in Example 1 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Linear sweep voltammetry curves of OER of high-entropy alloy strips in 1 M KOH electrolyte;

[0028] Figure 8 For the etching for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 When the high-entropy alloy strip is used as an electrolytic water OER catalytic material, the V-t diagram of constant current density at 20 mA / cm 2 and 50 mA / cm 2 in 1 M KOH electrolyte;

[0029] Figure 9 For the etching for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 When the high-entropy alloy strip is used as a full water splitting catalytic material, the linear sweep voltammetry curve in 1 M KOH electrolyte. Detailed implementation manners

[0030] The present invention will be further described in detail below.

[0031] Example 1

[0032] (1) Preparation of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip, the preparation process is as follows:

[0033] ① Weigh the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom, and under the protection of a high-purity argon atmosphere, remelt the alloy ingot at least 4 times by arc melting to ensure the uniformity of the alloy composition, and obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot;

[0034] ② Use the melt spinning quenching method to inductively melt the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot in an argon protection atmosphere, and spray the molten metal onto the surface of a copper roller rotating at 800 revolutions per minute through an instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25Cu 0.375 ) 40 Al 60 High-entropy alloy strip.

[0035] Figure 1 The 0h spectral line is the original (Fe prepared 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 X-ray diffraction pattern of the high-entropy alloy strip, showing that the strip has a duplex structure, and the two phases are the B2 phase and the body-centered cubic BCC phase respectively.

[0036] (2) Etch the above-prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 The high-entropy alloy strip is etched, and the processing process is as follows: The prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 The high-entropy alloy strip is etched in 3M KOH solution at room temperature for 2h, 4h, 6h, and 9h. The etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 The high-entropy alloy strip is washed successively with deionized water and absolute ethanol to remove the chemical substances remaining on the surface, and dried naturally at room temperature.

[0037] Figure 1 X-ray diffraction pattern of the high-entropy alloy strip prepared in this example as a function of etching time. As shown in the figure, the strip still maintains a duplex structure after etching, and the peak intensity of the BCC phase decreases slightly. 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 X-ray diffraction pattern of the high-entropy alloy strip prepared in this example as a function of etching time. As shown in the figure, the strip still maintains a duplex structure after etching, and the peak intensity of the BCC phase decreases slightly.

[0038] Figure 2 X-ray diffraction pattern of the high-entropy alloy strip prepared in this example as a function of etching time. As shown in the figure, the strip still maintains a duplex structure after etching, and the peak intensity of the BCC phase decreases slightly. 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60Scanning electron microscope images of the high-entropy alloy strip as a function of etching time. Among them, (a) original morphology, (b) morphology after etching for 2 h, (c) morphology after etching for 4 h, (d) morphology after etching for 6 h, (e) morphology after etching for 9 h. As shown in the figure, the surface of the original sample is relatively smooth and the specific surface area is limited. After etching in an alkaline solution, a mesoporous structure with a size of 50-350 nm is formed, which greatly increases the active specific surface area, exposes a large number of active sites, and improves the catalytic activity.

[0039] Figure 3 For the original (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Transmission electron microscope images of the high-entropy alloy strip; among them, (a) bright-field image of the original strip by transmission electron microscope, (b) selected area electron diffraction pattern of the B2 phase, (c) selected area electron diffraction pattern of the BCC phase. As shown in the figure, the original sample presents a duplex structure of B2 phase plus BCC phase, Figure 3 The superlattice diffraction spots in the selected area electron diffraction pattern in (b) confirm the B2 phase structure.

[0040] Figure 4 For the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 Transmission electron microscope images of the high-entropy alloy strip; among them, (a) selected area electron diffraction pattern of the BCC* phase, (b) high-resolution transmission electron microscope image of the BCC* phase, (c) high-resolution transmission electron microscope image of the NC phase, (d) Fourier transform image corresponding to (c). Among them, the B2 phase is etched to form the BCC* phase; the BCC phase is etched to form the NC phase. As shown in the figure, the original B2 phase becomes the BCC* phase after etching, Figure 4 The diffuse diffraction spots in the selected area electron diffraction pattern in (a), as shown by the dashed box, are the diffraction characteristics of the short-range ordered structure; the original BCC phase becomes the nanocrystalline NC phase after etching, Figure 4 The Fourier transform image in (d) shows the nano-polycrystalline structure characteristics of the NC phase.

[0041] Experiment 1: Comparison of alkaline HER performance of high-entropy alloy before and after etching

[0042] For the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60The electrochemical performance of the high-entropy alloy strip was tested as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was 1 M KOH solution.

[0043] Figure 5 In this example, the high-entropy alloy strip was etched for different times (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 HER linear sweep voltammetry curves of the high-entropy alloy strip in 1 M KOH electrolyte. As can be seen from the figure, when the current density was 10 mA cm -2 , after etching for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 The HER overpotential of the high-entropy alloy strip decreased from 221 mV before etching to 68 mV, indicating that the etching method can significantly improve the HER catalytic activity of the sample. Through density functional theory (DFT) calculations, it was proven in this invention that the short-range order structure in the BCC* phase promotes the adsorption of water molecules and the Gibbs free energy ΔG H* .

[0044] Figure 6 In this example, the high-entropy alloy strip etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 When used as an electrolytic water HER catalytic material, the high-entropy alloy strip had a constant current density V-t diagram at 20 mA / cm 2 and 50 mA / cm 2 in 1 M KOH electrolyte. As shown in the figure, after the HER reaction for 60 h, the overpotential increased slightly, indicating excellent stability of the sample.

[0045] Experiment 2: Comparison of the alkaline OER performance of the alloy before and after etching

[0046] Before and after etching (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60The electrochemical performance of the high-entropy alloy strip was tested as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was a 1 M KOH solution.

[0047] Figure 7 In this example, the high-entropy alloy strip was etched for different times (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 For the OER linear sweep voltammetry curve of the high-entropy alloy strip in 1 M KOH electrolyte, as can be seen from the figure, at a current density of 10 mA cm -2 , when etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 The OER overpotential of the high-entropy alloy strip decreased from 292 mV before etching to 235 mV, indicating that the etching method can significantly improve the OER catalytic activity of the sample. DFT calculations in this invention show that the OER reaction barrier of the reaction sites in the short-range order after etching is lower than that of the sites in the original strip, and the NC phase also has a lower OER reaction barrier. Therefore, the sample has excellent OER catalytic activity.

[0048] Figure 8 In this example, the high-entropy alloy strip etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 When the high-entropy alloy strip is used as an electrolytic water OER catalytic material, the V-t diagram at a constant current density of 20 mA / cm 2 and 50 mA / cm 2 in 1 M KOH electrolyte is shown in the figure. After 60 h of OER reaction, the overpotential increases slightly, indicating that the sample has excellent stability.

[0049] Experiment 3: Performance test of alkaline overall water splitting of the etched alloy for 4 h

[0050] For the etched 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60The high-entropy alloy strip was tested for overall water splitting performance. The testing process is as follows: A two-electrode working system was adopted, where both the anode and the cathode used the etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip of this example, and the electrolyte was 1 M KOH solution.

[0051] Figure 9 When the etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip was used as the overall water splitting catalytic material, the linear sweep voltammetry curve in 1 M KOH electrolyte was obtained. As can be seen from the figure, the etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip had excellent overall water splitting performance, and the overall water splitting potential was 1.58 V, indicating that the sample had alkaline bifunctional catalytic properties.

[0052] As can be seen from the above, through alkaline etching treatment (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 the high-entropy alloy strip could maintain self-support while constructing a surface nano-porous structure and a short-range ordered structure, increasing the active specific surface area, optimizing the local electronic structure, and improving the catalytic activity; among them, the etched for 4 h (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip had the best alkaline overall water splitting performance.

[0053] Example 2

[0054] (1) Preparation of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 high-entropy alloy strip, the preparation process is as follows:

[0055] ①Weigh the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom. Under the protection of a high-purity argon atmosphere, use the arc melting method to remelt the alloy ingot at least 4 times to ensure uniform alloy composition, and obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 master alloy ingot;

[0056] ②Use the melt spinning quenching method to inductively melt the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 master alloy ingot in an argon-protected atmosphere, and spray the molten metal onto the surface of a copper roller rotating at 800 revolutions per minute through an instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 high-entropy alloy strip.

[0057] (2) Etch the above-prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 high-entropy alloy strip, and the treatment process is as follows: Immerse the prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 high-entropy alloy strip in 3M KOH solution for etching, with the etching temperature at room temperature and the etching time at 2h, 4h, 6h, and 9h. Wash the etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 33 Al 67 high-entropy alloy successively with deionized water and absolute ethanol to remove the residual chemical substances, and then dry it naturally at room temperature.

[0058] Experiment 1: Comparison of the alkaline HER and OER performances of the high-entropy alloy before and after etching

[0059] For the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 )33 Al 67 The electrochemical performance of the high-entropy alloy strip was tested as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was 1 M KOH solution.

[0060] This composition has a relatively high aluminum content. Although it can still maintain a self-supporting structure after etching, the contents of the catalytically active elements iron, cobalt, and nickel decrease, so its performance is slightly worse than that of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy.

[0061] Example 3

[0062] (1) Preparation of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 high-entropy alloy strip, and the preparation process is as follows:

[0063] ① Weighed the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom. Under the protection of a high-purity argon atmosphere, the alloy ingot was remelted at least 4 times by arc melting to ensure the uniformity of the alloy composition, and (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 master alloy ingot was obtained;

[0064] ② The (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 master alloy ingot was inductively melted in an argon protection atmosphere, and the molten metal was sprayed onto the surface of a copper roller rotating at 800 revolutions per minute through an instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 high-entropy alloy strip.

[0065] (2) For the (Fe 0.25 Co 0.125 Ni 0.25 Cu0.375 ) 50 Al 50 The high-entropy alloy strip is etched, and the processing technology is as follows: The prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 The high-entropy alloy strip is etched in 3M KOH solution at room temperature for 2h, 4h, 6h, and 9h. The etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 The high-entropy alloy is washed successively with deionized water and absolute ethanol to remove the residual chemical substances, and then dried naturally at room temperature.

[0066] Experiment 1: Comparison of the alkaline HER and OER performances of the high-entropy alloy before and after etching

[0067] The electrochemical performance of the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 50 Al 50 high-entropy alloy strip before and after etching is tested. The test process is as follows: A three-electrode working system is adopted, where the working electrode is the high-entropy alloy strip prepared in this example, the counter electrode is a graphite rod, the reference electrode is a Hg / HgO electrode, and the electrolyte is 1M KOH solution.

[0068] The aluminum content in this composition is relatively low. Although a nanoporous structure can still be formed on the surface after etching, the leaching of aluminum elements during etching is limited, the atomic rearrangement is restricted, and the ability to optimize the local electronic structure is limited. Therefore, the performance is slightly worse than that of the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy.

[0069] Example 4

[0070] (1) Prepare a (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip. The preparation process is as follows:

[0071] ① Weigh the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom. Under the protection of a high-purity argon atmosphere, use the arc melting method to remelt the alloy ingot at least 4 times to ensure uniform alloy composition, and obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot;

[0072] ② Use the melt spinning quenching method to inductively melt the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot in an argon-protected atmosphere, and spray the molten metal onto the surface of a copper roller rotating at 700 revolutions per minute through instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip.

[0073] (2) Etch the above-prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip. The treatment process is as follows: Immerse the prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip in 3M KOH solution for etching. The etching temperature is room temperature, and the etching times are 2h, 4h, 6h, and 9h. Wash the etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip successively with deionized water and absolute ethanol to remove the chemical substances remaining on the surface, and dry it naturally at room temperature.

[0074] Experiment 1: Comparison of the alkaline HER performance of the high-entropy alloy before and after etching

[0075] For the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 )40 Aluminum 60 The electrochemical performance of the high-entropy alloy strip was tested, and the test process was as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was 1 M KOH solution.

[0076] Experiment 2: Comparison of the alkaline OER performance of the alloy before and after etching

[0077] Before and after etching (Fe 0.25 Cobalt 0.125 Nickel 0.25 Copper 0.375 ) 40 Aluminum 60 The electrochemical performance of the high-entropy alloy strip was tested, and the test process was as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was 1 M KOH solution.

[0078] The strip prepared at this rotation speed was thicker and had a greater self-weight than the strip obtained in Example 1, but it could still maintain the duplex high-entropy alloy structure. After etching, nanopores were formed on the surface of the strip, and the HER and OER performances were similar to those of the sample in Example 1.

[0079] Example 5

[0080] (1) Preparation of (Fe 0.25 Cobalt 0.125 Nickel 0.25 Copper 0.375 ) 40 Aluminum 60 high-entropy alloy strip, and the preparation process was as follows:

[0081] ① Weighed the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the atomic molar percentage content, and under the protection of a high-purity argon atmosphere, the alloy ingot was remelted at least 4 times by arc melting to ensure the uniformity of the alloy composition, and (Fe 0.25 Cobalt 0.125 Nickel 0.25 Copper 0.375 ) 40 Aluminum 60 master alloy ingot;

[0082] ② The (Fe 0.25 Cobalt 0.125 Nickel 0.25 Copper 0.375 ) 40 Aluminum 60 master alloy ingot was inductively melted in an argon protection atmosphere, and the molten metal was sprayed onto the surface of a copper roller rotating at 1000 revolutions per minute through an instantaneous pressure difference to obtain (Fe0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 High-entropy alloy strip.

[0083] (2) Etch the above-prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip, and the treatment process is as follows: Immerse the prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip in 3M KOH solution for etching, the etching temperature is room temperature, and the etching times are 2h, 4h, 6h, and 9h. Wash the etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip successively with deionized water and absolute ethanol to remove the residual chemical substances on the surface, and then dry it naturally at room temperature.

[0084] Experiment 1: Comparison of the alkaline HER performance of the high-entropy alloy before and after etching

[0085] Perform electrochemical performance tests on the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip before and after etching. The test process is as follows: Adopt a three-electrode working system, where the working electrode is the high-entropy alloy strip prepared in this example, the counter electrode is a graphite rod, the reference electrode is a Hg / HgO electrode, and the electrolyte is 1M KOH solution.

[0086] Experiment 2: Comparison of the alkaline OER performance of the alloy before and after etching

[0087] Perform electrochemical performance tests on the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60The electrochemical performance of the high-entropy alloy strip was tested as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was 1 M KOH solution.

[0088] XRD testing showed that the high-entropy alloy strip prepared at this rotation speed was still a duplex structure, with no obvious difference in surface morphology from the sample in Example 1. After etching, a nanoporous structure was formed, and the HER and OER performances were similar to those of the sample in Example 1. The combination of Examples 4 and 5 indicated that this composition system could stably obtain the expected structure and performance within a relatively wide rotation speed range.

[0089] Comparative Example 1

[0090] (1) Preparation of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip, and the preparation process was as follows:

[0091] ① Weighed the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the atomic molar percentage content of each, and under the protection of a high-purity argon atmosphere, the alloy ingot was remelted at least 4 times by arc melting to ensure the uniformity of the alloy composition, and obtained (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot;

[0092] ② The (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot was inductively melted in an argon protection atmosphere, and the molten metal was sprayed onto the surface of a copper roller rotating at 800 revolutions per minute through an instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip.

[0093] (2) For the above-prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60The high-entropy alloy strip is etched, and the processing technology is as follows: The prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip is etched in 8M KOH solution at room temperature for 10 min, 20 min, 30 min, 40 min, 1 h, and 1.5 h. The etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy is successively washed with deionized water and absolute ethanol to remove residual chemical substances and dried naturally at room temperature.

[0094] Experiment 1: Comparison of the alkaline HER and OER performances of the high-entropy alloy before and after etching

[0095] The electrochemical performance of the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip before and after etching is tested. The testing process is as follows: A three-electrode working system is adopted, where the working electrode is the high-entropy alloy strip prepared in this example, the counter electrode is a graphite rod, and the reference electrode is a Hg / HgO electrode. The electrolyte is 1M KOH solution.

[0096] Due to the too high concentration of the etching solution, aluminum atoms are leached out rapidly and in large quantities. The un-leached atoms still remain in a state with a high degree of disorder after a short rearrangement and it is difficult to form a large number of ordered structures, so the catalytic effect is worse than that of etching with 3M KOH solution.

[0097] Comparative Example 2

[0098] (1) Prepare a (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip. The preparation process is as follows:

[0099] ① Weigh the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom. Under the protection of a high-purity argon atmosphere, the alloy ingot is remelted at least 4 times by arc melting to ensure the uniform alloy composition, and obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 )40 Al 60 Master alloy ingot

[0100] ② Using the melt spinning quenching method, (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 The master alloy ingot is inductively melted in an argon - protected atmosphere, and the molten metal is sprayed onto the surface of a copper roller rotating at 800 revolutions per minute through an instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 High - entropy alloy strips.

[0101] (2) Etching treatment is carried out on the above - prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 High - entropy alloy strips, and the treatment process is as follows: The prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 High - entropy alloy strips are etched in a 0.5 M KOH solution at room temperature for etching times of 6 h, 8 h, 10 h, and 12 h. The etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 High - entropy alloy strips are successively washed with deionized water and absolute ethanol to remove residual chemical substances and then naturally dried at room temperature. Since the etching solution concentration is low, the etching rate is very slow, and there are still bubbles on the strip surface after 12 h of etching, and the efficiency is too low.

[0102] Comparative Example 3

[0103] (1) Preparation of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 High - entropy alloy strips, and the preparation process is as follows:

[0104] ①Weigh the raw materials of high-purity iron, cobalt, nickel, copper, and aluminum according to the molar percentage content of each atom. Under the protection of a high-purity argon atmosphere, use the arc melting method to remelt the alloy ingot at least 4 times to ensure uniform alloy composition, and obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot;

[0105] ②Adopt the melt spinning quenching method to inductively melt the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 master alloy ingot in an argon protection atmosphere, and spray the molten metal onto the surface of a copper roller rotating at 800 revolutions per minute through instantaneous pressure difference to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip.

[0106] (2)Etch the above-prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip, and the treatment process is as follows: Immerse the prepared (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy strip in 3M KOH solution for etching, the etching temperature is room temperature, and the etching time is 10h, 11h, and 12h. Wash the etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 40 Al 60 high-entropy alloy successively with deionized water and absolute ethanol to remove residual chemical substances, and dry it naturally at room temperature.

[0107] Experiment 1: Comparison of alkaline HER and OER performance of high-entropy alloy before and after etching

[0108] For the (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 )40 Al 60 The electrochemical performance of the high-entropy alloy strip was tested as follows: A three-electrode working system was adopted, where the working electrode was the high-entropy alloy strip prepared in this example, the counter electrode was a graphite rod, the reference electrode was a Hg / HgO electrode, and the electrolyte was a 1M KOH solution.

[0109] At this etching solution concentration, there were no obvious bubbles on the strip surface at 10 h, indicating that the etching process had basically ended, and further extending the etching time had no promoting effect on the performance.

[0110] Comparative Example 4

[0111] (1) Preparation of (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 The high-entropy alloy strip was prepared as follows:

[0112] ① The raw materials of high-purity iron, cobalt, nickel, copper, and aluminum were weighed according to the molar percentage content of each atom. Under the protection of a high-purity argon atmosphere, the alloy ingot was remelted at least 4 times by arc melting to ensure uniform alloy composition, and a (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 master alloy ingot was obtained;

[0113] ② The (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 master alloy ingot was induction melted in an argon protection atmosphere, and the molten metal was sprayed onto the surface of a copper roller rotating at 800 revolutions per minute through instantaneous pressure difference to obtain a (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 high-entropy alloy strip.

[0114] (2) The (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 high-entropy alloy strip prepared above was etched, and the treatment process was as follows: The prepared (Fe 0.25 Co0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 The high-entropy alloy strip is etched in 3 M KOH solution at room temperature for etching times of 2 h, 4 h, 6 h, and 9 h. The etched (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 20 Al 80 The high-entropy alloy is successively cleaned with deionized water and absolute ethanol to remove residual chemical substances and is naturally dried at room temperature.

[0115] Due to the excessive aluminum content, after the aluminum element is removed in the KOH solution, the strip breaks and cannot maintain a self-supporting structure, resulting in the deterioration of the catalytic performance.

Claims

1. A self-supporting porous high-entropy alloy overall water splitting catalytic material, characterized in that, In terms of the molar percentage content of each atom, the chemical formula is (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100-x Al x , where 50 ≤ x ≤ 67; the self-supporting porous high-entropy alloy overall water splitting catalytic material is obtained by alkali etching of a high-entropy alloy strip.

2. A preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 1, characterized in that, comprises the following steps: (1) Weigh iron, cobalt, nickel, copper, and aluminum raw materials according to the molar percentage content of each atom; (2) Arc melt the raw materials to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100-x Al x master alloy ingot; (3) The obtained master alloy ingot was processed by melt spinning quenching to obtain (Fe 0.25 Co 0.125 Ni 0.25 Cu 0.375 ) 100-x Al x high entropy alloy strip; (4) Subject the obtained high-entropy alloy strip to alkali etching, followed by washing and drying to obtain the self-supporting porous high-entropy alloy overall water splitting catalytic material.

3. The preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 2, characterized in that, the concentration of alkali etching in step (4) is 1 - 6 M.

4. The preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 2, characterized in that, the time of alkali etching in step (4) is 0.5 - 12 h.

5. The preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 2, characterized in that, the medium of alkali etching in step (4) is KOH solution.

6. The preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 2, characterized in that, in step (3), the rotational speed of the copper roller in the melt spinning quenching method is 700 - 1000 revolutions per minute.

7. The preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 2, characterized in that, in step (2), argon is used as the protective atmosphere in the arc melting method, and remelting is performed at least 4 times to ensure uniform alloy composition.

8. The preparation method of the self-supporting porous high-entropy alloy overall water splitting catalytic material according to claim 2, characterized in that, argon is used as the protective atmosphere in step (3) of the melt spinning quenching technique.

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