NiCoW-CoP / Co3O4-coated NF self-supporting heterostructure catalyst and preparation method thereof

Abstract

The invention relates to a NiCoW-CoP / Co3O4 (at) NF self-supporting heterostructure catalyst and a preparation method thereof. The preparation method comprises the following steps: preparing a CoP-coated NF precursor on foamed nickel through a constant potential electrodeposition method, then carrying out annealing treatment in a muffle furnace, and finally carrying out electrodeposition on NiCoW-LDH to obtain the NiCoW-CoP / Co3O4-coated NF material. According to the preparation method, the microsphere material with the surface covered with the dendritic dendrites is synthesized, and exposure of active sites is increased through the special surface structure of the microsphere material. The compounding of the trimetal hydroxide containing high-valence tungsten and the introduction of oxygen vacancies can effectively enhance the local electron density of oxygen atoms on the surface of the catalyst, thereby enhancing the catalytic performance and seawater corrosion resistance of the material. Compared with the prior art, the method disclosed by the invention is simple to operate and low in cost, and the prepared catalyst has high electrocatalytic activity, relatively low hydrogen evolution overpotential and oxygen evolution overpotential and long-time stability. And the method has important theoretical significance and potential application value for developing a bifunctional electrocatalyst suitable for electrolyzing seawater.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalytic water splitting catalysts, and particularly to a NiCoW-CoP / Co3O4@NF self-supporting heterostructure catalyst and a preparation method thereof. Background Art

[0003] Electrolytic water splitting for hydrogen production has attracted much attention due to advantages such as simple raw materials, no greenhouse gas emissions, high hydrogen production efficiency, and high product purity. Compared with using scarce fresh water as the electrolyte solution, preparing hydrogen and oxygen using resource-rich seawater shows a broader development prospect. Nevertheless, the seawater electrolysis process faces many challenges, such as corrosion problems caused by chlorides, the presence of harmful ions, bacteria, microorganisms, and microparticles, which may all damage the performance and long-term stability of electrocatalysts. In addition, there is an electrochemical competitive reaction between the oxygen evolution reaction and the chlorine evolution reaction on the anode side, further increasing the technical difficulty. Therefore, developing electrocatalysts suitable for high-current-density seawater electrolysis with high intrinsic activity and stability is a prerequisite for the commercialization of seawater electrolysis technology.

[0004] Among emerging electrocatalytic materials, transition metal phosphides (TMPs) have received increasing attention in the field of hydrogen evolution reaction (HER) due to their low resistance, excellent mechanical strength, chemical stability, and their inherent high-efficiency Cl - exclusion characteristics. When phosphorus enters the metal lattice, the presence of phosphorus can dilute metal atoms and maintain the original electronic properties of the metal, thereby reducing the free energy of hydrogen adsorption and facilitating the desorption of hydrogen. Among them, the excellent HER performance of cobalt phosphide (CoP) catalysts can be attributed to their abundant active sites and moderate Gibbs free energy of H adsorption (ΔG H* ). However, high activation energy limits their hydrogen production rate and reduces their catalytic activity. Layered double hydroxides (LDHs) have received more attention from researchers worldwide due to their abundance, low cost, and high stability under alkaline conditions. However, due to problems such as low conductivity and insufficient water-activated active sites under alkaline conditions, most LDHs still cannot show effective HER activity. Among them, compared with bimetallic hydroxides, ternary metal hydroxides have higher catalytic activity due to their layered structure and mixed valence state. Therefore, combining ternary metal hydroxides with TMPs to form a transition metal layered hydroxide (TM-LDH) heterostructure, using the compounding of trimetallic hydroxides containing high-valence tungsten and the introduction of oxygen vacancies to increase the local electron density of oxygen atoms on the catalyst surface, thereby improving the catalytic performance and corrosion resistance of the material, and achieving efficient and stable seawater decomposition. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a

[0006] NiCoW-CoP / Co3O4@NF self-supporting heterostructure catalyst and its preparation method. This method is simple and efficient, and an electrolytic water catalyst with excellent hydrogen evolution activity and oxygen evolution activity can be prepared by simple electrodeposition and high-temperature calcination methods. This catalyst can exhibit long-term stability at high current densities and can also be effectively applied to the process of seawater electrolysis.

[0007] The preparation method of the NiCoW-CoP / Co3O4@NF self-supporting heterostructure composite catalyst provided by the present invention includes the following steps:

[0008] Step 1: First, a piece of nickel foam with a size of 1×2 cm 2 is sonicated in 3M HCl, absolute ethanol, and ultrapure water for 15 minutes respectively to remove possible surface oxides and organic impurities;

[0009] Step 2: The nickel foam (NF) treated in Step 1 is electrochemically deposited in a CoP electrodeposition solution in a three-electrode system by potentiostatic deposition method. Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and NF is used as the working electrode. The deposition voltage is -1 to (-1.4) V, and the deposition time is 1500 to 2000 s. After the reaction, it is washed and dried to obtain precursor 1;

[0010] Step 3: The precursor 1 is calcined in a muffle furnace at a calcination temperature of 250 to 300 °C for 40 - 80 minutes to obtain precursor 2;

[0011] Step 4: The precursor 2 obtained in Step 3 is electrochemically deposited in a NiCoW-LDH electrodeposition solution in a three-electrode system again by potentiostatic deposition method. Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and precursor 2 is used as the working electrode. The deposition voltage is -1 to (-1.4) V, and the deposition time is 100 to 300 s. After the reaction, it is washed and dried to obtain the NiCoW-CoP / Co3O4@NF self-supporting heterostructure catalyst.

[0012] The present invention has the following advantages compared with most existing electrocatalyst materials:

[0013] 1. The present invention synthesizes a preparation method of a NiCoW-CoP-Co3O4@NF self-supporting heterostructure catalyst. The preparation process is simple, the raw materials are widely available, and it is green and economical. The three-dimensional porous heterojunction catalyst prepared by using this strategy exhibits excellent electrocatalytic activity under 1MKOH alkaline conditions, with 10 mA / cm 2When the current density is [value], the overpotentials corresponding to the hydrogen evolution and oxygen evolution reactions are only 54.62 mV and 260.12 mV, and the Tafel slopes are 69.98 mV / dec and 45.68 mV / dec respectively, which can maintain long-term stability at high current densities. And this material has good hydrogen evolution activity and oxygen evolution activity both in simulated seawater and real seawater environments.

[0014] 2. The present invention directly synthesizes a microsphere material with dendritic branches covering the surface on nickel foam through simple electrodeposition and high-temperature calcination methods. This unique morphology not only provides abundant pores, increases the exposure of active sites, but also accelerates the charge-mass transfer, enabling the electrocatalyst to improve the hydrogen evolution activity and oxygen evolution activity while maintaining long-term stability.

[0015] 3. The present invention introduces a trimetallic layered hydroxide NiCoW-LDH composed of a high-valent metal element tungsten (W) through a simple electrodeposition method. Under the action of WO4 2- Co is oxidized to Co 2+ , and then together with Ni 3+ and WO4 2+ is electrodeposited to form a Ni-Co-W hydroxide. The empty d orbitals of W effectively regulate the electronic structures of Ni and Co, and the synergistic effect generated with the host cations enables it to exhibit excellent OER performance and can be used for seawater electrolysis 2-

[0016] 4. The synthesized NiCoW-CoP / Co3O4@NF three-dimensional porous heterojunction catalyst of the present invention combines NiCoW-LDH and CoP to form a heterostructure. By effectively exposing the active centers and regulating the electronic structures, it overcomes the individual limitations of LDHs and TMPs in the water splitting reaction and realizes bifunctional catalysis. During the HER process, there is a strong interfacial interaction between CoP and NiCoW-LDH. This synergistic effect regulates the adsorption of H + on CoP and the adsorption of OH - on NiCoW-LDH, promotes the adsorption of water molecules and OH - intermediates and the dissociation of O-H bonds. The formed protons tend to adsorb on the negatively charged metal sites around the CoP surface and combine with the adjacent hydrogen adsorption sites, accelerating the HER process. During the OER process, the construction of the heterostructure is beneficial to establishing highly active M─OOH intermediate substances at lower potentials, thereby improving the catalytic activity of OER. Compared with pure NiCoW-LDH and pure CoP, NiCoW-CoP / Co3O4@NF is more likely to adsorb OH - -, thus promoting the catalytic performance of OER. In addition, this catalyst can effectively inhibit the competition between the chloride oxidation reaction (ClOR) initiated by chloride anions in natural seawater and the oxygen evolution reaction (OER) at the anode, enabling efficient seawater electrolysis.

[0017] 5. The introduction of oxygen vacancies (Ov) has been proven to be an important strategy for improving catalytic performance. In this invention, a CoP / Co3O4 composite material rich in oxygen vacancies is prepared by high-temperature calcination of a CoP precursor. The introduction of oxygen vacancies changes the surface electron configuration, generating mid-gap electron states, thereby enhancing electron conductivity, promoting the cleavage of the H-OH bond, and optimizing the hydrogen adsorption free energy (ΔG H* ). In addition, by synergistically introducing a trimetallic hydroxide containing a high-valent tungsten and oxygen vacancies, the local electron density of oxygen atoms on the catalyst surface is significantly increased. This synergistic effect not only enhances the electrocatalytic performance of the catalyst but also improves its corrosion resistance BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Comparison diagram of HER polarization curves of Example 1, Comparative Examples 1-3, and 20% Pt / C in 1 M KOH electrolyte;

[0019] Figure 2 Comparison diagram of OER polarization curves of Example 1, Comparative Examples 1-3, and IrO2 in 1 M KOH electrolyte;

[0020] Figure 3 Comparison diagram of Tafel slopes of hydrogen evolution of Example 1, Comparative Examples 1-3, and 20% Pt / C in 1 M KOH electrolyte;

[0021] Figure 4 Comparison diagram of Tafel slopes of oxygen evolution of Example 1, Comparative Examples 1-3, and IrO2 in 1 M KOH electrolyte;

[0022] Figure 5 For Example 1, Comparative Examples 1-3, and 20% Pt / C in 1 M KOH electrolyte, the current density is 10 mA cm -2 and 100 mA cm -2 Hydrogen evolution overpotential comparison diagram;

[0023] Figure 6 For Example 1, Comparative Examples 1-3, and IrO2 in 1 M KOH electrolyte, the current density is 10 mA cm -2 and 100 mA cm -2 Oxygen evolution overpotential comparison diagram;

[0024] Figure 7EIS test curves of Example 1 and Comparative Examples 1-3 at the HER potential in 1 M KOH electrolyte;

[0025] Figure 8 EIS test curves of Example 1 and Comparative Examples 1-3 at the OER potential in 1 M KOH electrolyte;

[0026] Figure 9 Hydrogen evolution reaction stability test curve of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH electrolyte at a current density of 100 mA cm -2 -2;

[0027] Figure 10 Oxygen evolution reaction stability test curve of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH electrolyte at a current density of 100 mA cm-2;

[0028] Figure 11 Comparison diagram of HER polarization curves of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH electrolyte before and after 5000 cycles;

[0029] Figure 12 Comparison diagram of OER polarization curves of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH electrolyte before and after 5000 cycles;

[0030] Figure 13 Comparison diagram of HER polarization curves of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH, 1 M KOH + 0.5 M NaCl and 1 M KOH + seawater electrolytes;

[0031] Figure 14 Comparison diagram of OER polarization curves of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH, 1 M KOH + 0.5 M NaCl and 1 M KOH + seawater electrolytes;

[0032] Figure 15 SEM image of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1;

[0033] Figure 16 TEM image of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1;

[0034] Figure 17 HRTEM image of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1;

[0035] Figure 18 XRD pattern of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1. Detailed implementation manners

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners. It should be noted that, on the premise of no conflict, the following-described embodiments can be combined arbitrarily to form new embodiments.

[0037] Example 1:

[0038] The preparation method and

[0039] application of the NiCoW-CoP / Co3O4@NF self-supporting heterostructure catalyst provided in this example are as follows:

[0040] (1) Place a 1×2 cm 2 NF in 3M HCl, absolute ethanol, and ultrapure water respectively for ultrasonic treatment for 15 min to remove possible oxides and organic impurities on the surface, and then put it in an oven at 60 °C for drying for 6 h for standby.

[0041] (2) Use the NF treated in step (1) as the electrodeposition solution with an aqueous solution containing 0.01 - 0.08 M sodium hypophosphite, 0.01 - 0.08 M cobalt sulfate, and 0.01 - 0.08 M sodium sulfate. Electrochemical deposition is carried out by potentiostatic electrodeposition method in a three-electrode system. Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and NF is used as the working electrode. The deposition voltage is -1.1 - (-1.4) V, and the deposition time is 1500 - 2000 s. After the deposition, rinse repeatedly with ultrapure water and absolute ethanol, and then put it in an oven at 60 °C for drying for 30 min to obtain CoP@NF.

[0042] (3) Place the CoP@NF obtained in step (2) in a muffle furnace for calcination. The calcination temperature is 250 - 300 °C, and the calcination time is 40 - 80 min to obtain CoP / Co3O4@NF.

[0043] (4) The CoP / Co3O4@NF obtained in step (3) is used as an electroplating solution with an aqueous solution containing 0.005 - 0.1 M nickel nitrate, 0.005 - 0.1 M cobalt nitrate, and (5) 0.005 - 0.1 M sodium tungstate, with a pH of 1 - 4. Electrochemical deposition is carried out again by potentiostatic electroplating method in a three-electrode system. Ag / AgCl is used as the reference electrode, a platinum sheet is used as the counter electrode, and CoP / Co3O4@NF is used as the working electrode. The deposition voltage is -1.1 - (-1.4) V, and the deposition time is 100 - 300 s. After the deposition, it is repeatedly rinsed with ultrapure water and absolute ethanol, and then placed in an oven to dry at 60 °C for 30 min to obtain the NiCoW-CoP / Co3O4@NF electrolytic water catalyst.

[0044] Comparative Example 1

[0045] The difference between Comparative Example 1 and Example 1 is that only steps (1) and (2) are carried out to obtain CoP@NF.

[0046] Comparative Example 2

[0047] The difference between Comparative Example 2 and Example 1 is that step (4) is omitted, and the rest is the same as Example 1 to obtain CoP / Co3O4@NF.

[0048] Comparative Example 3

[0049] The difference between Comparative Example 3 and Example 1 is that steps (2) and (3) are omitted, the working electrode in step (4) is changed to the NF treated in step (1), and the rest is the same as Example 1 to obtain NiCoW-LDH@NF.

[0050] Experimental Example 1:

[0051] The products obtained in Example 1 and Comparative Examples 1 to 3 are used as catalysts for HER testing and OER testing in 1 M KOH, 1 M KOH + 0.5 M NaCl, and 1 M KOH + seawater electrolytes. The electrochemical tests are carried out on an electrochemical workstation (CHI660D), using a standard three-electrode system, where the Hg / HgO electrode is used as the reference electrode, the graphite rod electrode is used as the counter electrode, and the products prepared in Example 1 and Comparative Examples 1 to 3 of the present invention are used as the working electrodes (geometric area 1 cm × 1 cm). Linear sweep voltammetry (LSV) is measured at a scanning rate of 5 mV s -1 . And 90% iR compensation is carried out. The iR correction is carried out according to the following formula: E corr = E mea - iR (Ecorr is the iR compensation potential, E mea is the experimental measurement potential, and R is the solution resistance). Electrochemical impedance spectroscopy (EIS) is carried out at 0.01 - 10 6It was carried out in the frequency range of Hz, and the potential amplitude was 5 mV. At a current density of 100 mA / cm -2 Under the condition of, the electrochemical stability was tested by chronoamperometry curve.

[0052] Figure 1 Figure 1 is a comparative diagram of HER polarization curves of Example 1, Comparative Examples 1-3 and 20% Pt / C in 1 M KOH electrolyte. It can be seen from Figure 1 that the NiCoW-CoP / Co3O4@NF material has a hydrogen evolution overpotential of 54.62 mV at a current density of 10 mA / cm -2 , which is better than other comparative examples. It shows that under the synergistic effect of the combination of CoP and NiCoW-LDH materials and oxygen vacancy regulation, the NiCoW-CoP / Co3O4@NF material exhibits excellent hydrogen evolution performance in alkaline electrolyte.

[0053] Figure 2 Figure 2 is a comparative diagram of OER polarization curves of Example 1, Comparative Examples 1-3 and IrO2 in 1 M KOH electrolyte. It can be seen from Figure 2 that the NiCoW-CoP / Co3O4@NF material has an oxygen evolution overpotential of 260.12 mV at a current density of 10 mA / cm -2 , which is better than other comparative examples. It shows that under the synergistic effect of the combination of CoP and NiCoW-LDH materials and oxygen vacancy regulation, the NiCoW-CoP / Co3O4@NF material exhibits excellent oxygen evolution performance in alkaline electrolyte.

[0054] Figure 3 Figure 3 is a comparative diagram of Tafel slopes of hydrogen evolution of Example 1, Comparative Examples 1-3 and 20% Pt / C in 1 M KOH electrolyte. It can be seen from Figure 3 that the Tafel slope of the hydrogen evolution reaction of the NiCoW-CoP / Co3O4@NF material is 69.98 mV / dec, which is better than other comparative examples. It shows that under the synergistic effect of the combination of CoP and NiCoW-LDH materials and oxygen vacancy regulation, the NiCoW-CoP / Co3O4@NF material exhibits excellent hydrogen evolution performance in alkaline electrolyte.

[0055] Figure 4 Figure 4 is a comparative diagram of Tafel slopes of oxygen evolution of Example 1, Comparative Examples 1-3 and IrO2 in 1 M KOH electrolyte. It can be seen from Figure 4It can be seen from [reference] that the Tafel slope of the NiCoW-CoP / Co3O4@NF material for the oxygen evolution reaction is 45.68 mV / dec, which is better than the Tafel slope comparison diagrams of other comparative examples and better than other comparative examples. This shows that under the synergistic effect of the combination of CoP and NiCoW-LDH materials and oxygen vacancy regulation, the NiCoW-CoP / Co3O4@NF material exhibits excellent oxygen evolution performance in alkaline electrolyte.

[0056] Figure 5 Figure showing the comparison of hydrogen evolution overpotentials of Example 1, Comparative Examples 1-3, and 20% Pt / C at current densities of 10 mA cm -2 and 100 mA cm -2 in 1 M KOH electrolyte. It can be seen from Figure 5 that the NiCoW-CoP / Co3O4@NF material has better hydrogen evolution overpotentials than other comparative examples at current densities of 10 mA cm -2 and 100 mA cm -2 . This shows that the NiCoW-CoP / Co3O4@NF material also exhibits excellent hydrogen evolution catalytic activity at high current densities.

[0057] Figure 6 Figure showing the comparison of oxygen evolution overpotentials of Example 1, Comparative Examples 1-3, and IrO2 at current densities of 10 mA cm -2 and 100 mA cm -2 in 1 M KOH electrolyte. It can be seen from Figure 6 that the NiCoW-CoP / Co3O4@NF material has better oxygen evolution overpotentials than other comparative examples at current densities of 10 mA cm -2 and 100 mA cm -2 . This shows that the NiCoW-CoP / Co3O4@NF material also exhibits excellent oxygen evolution catalytic activity at high current densities.

[0058] Figure 7 EIS test curves of Example 1, Comparative Examples 1-3 at HER potential in 1 M KOH electrolyte. It can be seen from Figure 7 that the NiCoW-CoP / Co3O4@NF material has the minimum impedance, that is, the best conductivity, which is beneficial to reducing the polarization phenomenon of the catalyst during the catalytic process and can effectively reduce the overpotential of the catalyst during the catalytic process. It is proved that the combination of CoP and NiCoW-LDH materials and oxygen vacancy regulation plays a crucial role in improving the conductive structure of the catalyst.

[0059] Figure 8 EIS test curves of Example 1, Comparative Examples 1-3 at OER potential in 1 M KOH electrolyte. It can be seen from Figure 8It can be seen from [the relevant content] that the NiCoW-CoP / Co3O4@NF material has the minimum impedance, that is, the best conductivity, which is beneficial to reducing the polarization phenomenon of the catalyst during the catalytic process and can effectively reduce the overpotential of the catalyst during the catalytic process. It is proved that the combination of CoP and NiCoW-LDH materials and oxygen vacancy regulation play a crucial role in improving the conductive structure of the catalyst

[0060] Figure 9 For NiCoW-CoP / Co3O4@NF in 1 M KOH electrolyte, the current density is 100 mA cm -2 This is the hydrogen evolution reaction stability test curve at [a certain time], and the electrolysis water reaction shows almost no attenuation in nearly 100 h.

[0061] Figure 10 For NiCoW-CoP / Co3O4@NF in 1 M KOH electrolyte, the current density is 100 mA cm -2 This is the oxygen evolution reaction stability test curve at [a certain time], and the electrolysis water reaction shows almost no attenuation in nearly 100 h;

[0062] Figure 11 This is the comparison chart of HER polarization curves of NiCoW-CoP / Co3O4@NF before and after 5000 cycles in 1 M KOH electrolyte, indicating that the hydrogen evolution performance after 5000 cycles does not decrease significantly;

[0063] Figure 12 This is the comparison chart of OER polarization curves of NiCoW-CoP / Co3O4@NF before and after 5000 cycles in 1 M KOH electrolyte, indicating that the LSV curve after 5000 cycles is almost the same as the original curve, and the displacement can be ignored

[0064] Figure 13 This is the comparison chart of HER polarization curves of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH, 1 M KOH + 0.5 M NaCl and 1 M KOH + seawater electrolytes, indicating that this material has good hydrogen evolution activity whether in simulated seawater or real seawater environment;

[0065] Figure 14 This is the comparison chart of OER polarization curves of NiCoW-CoP / Co3O4@NF prepared by the method of Example 1 in 1 M KOH, 1 M KOH + 0.5 M NaCl and 1 M KOH + seawater electrolytes, indicating that this material has good oxygen evolution activity whether in simulated seawater or real seawater environment.

[0066] In summary, the present invention forms a stable three-dimensional porous heterojunction catalyst on nickel foam through a simple electro-deposition-calcination-electro-deposition method. This catalyst can effectively reduce the polarization phenomenon during the electrolysis of water, exhibit a lower overpotential during the catalytic process, demonstrate long-term stability at a high current density, and can also be effectively applied to the electrolysis of seawater.

[0067] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A preparation method of a NiCoW-CoP / Co3O4@NF self-supporting heterostructure catalyst, comprising the following steps: (1) After cleaning the nickel foam (NF), in a three-electrode system, electrochemical deposition is carried out in a CoP electrodeposition solution by potentiostatic deposition method. After the deposition is completed, it is washed and dried to obtain precursor 1; (2) The precursor 1 is placed in a muffle furnace and calcined at high temperature to obtain precursor 2; (3) The precursor 2 obtained in step (2) is in a three-electrode system, and electrochemical deposition is carried out again in a NiCoW-LDH electrodeposition solution by potentiostatic deposition method. After the deposition is completed, it is washed and dried to obtain the electrolytic water catalyst.

2. The step method according to step (1) of claim 1, characterized in that Put a 1×2 cm piece of nickel foam 2 in 3M HCl, absolute ethanol, and ultrapure water respectively, and perform ultrasonic treatment for 15 min to remove possible oxides and organic impurities on the surface.

3. The step method according to step (1) of claim 1, characterized in that The three-electrode system uses Ag / AgCl as the reference electrode, a platinum sheet as the counter electrode, and NF as the working electrode. The deposition voltage is -1 to (-1.4) V, and the deposition time is 1500 to 2000 s.

4. The step method according to step (1) of claim 1, characterized in that The electrodeposition solution is an aqueous solution containing 0.01 to 0.08 M sodium hypophosphite, 0.01 to 0.08 M cobalt sulfate, and 0.01 to 0.08 M sodium sulfate.

5. The step method according to step 1) of claim 1, characterized in that, The washing solution is ultrapure water and absolute ethanol. The drying time is 30 min, and the drying temperature is 60 °C.

6. The step method according to step (2) of claim 1, characterized in that, The calcination temperature is 250 to 300 °C, and the calcination time is 40 - 80 min.

7. The step method according to step (3) of claim 1, characterized in that, The three-electrode system uses Ag / AgCl as the reference electrode, a platinum sheet as the counter electrode, and precursor 2 as the working electrode. The deposition voltage is -1.1 to (-1.4) V, and the deposition time is 100 to 300 s.

8. The step method according to step (3) of claim 1, characterized in that, The electrodeposition solution is an aqueous solution containing 0.005 to 0.1 M nickel nitrate, 0.005 to 0.1 M cobalt nitrate, and 0.005 to 0.1 M sodium tungstate, with a pH of 1 to 4.

9. The step method according to step (3) of claim 1, characterized in that The washing solution is ultrapure water and absolute ethanol. The drying time is 30 min, and the drying temperature is 60 °C.

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