Electrocatalyst and its preparation method and application

Abstract

The present invention belongs to the technical field of electrocatalysis, and discloses an electrocatalyst and its preparation method and application. The method comprises the following steps: using a corrosive solution to contact and react with a nickel substrate to obtain an electrocatalyst. A solution containing ferric chloride, cobalt chloride and sodium thiosulfate is used as a corrosive solution to produce a Ni-containing catalyst in the local area of ​​the Ni substrate. 2+ 、Fe 2+ 、Co 2+ OH ‑ 、S 2‑ microenvironment. Specifically, S2O4 2‑ and Cl ‑ Coexistence will cause pitting corrosion of the Ni substrate and release Ni 2+ ;S2O4 2‑ The redox and weak alkalinity can release S 2‑ and OH ‑ ; Controlling the ratio of Fe and Co in the corrosion solution can regulate the Co 2+ Due to the small solubility constant of the precipitates obtained from the above metal ions and anions, the pitting effect and precipitation reaction coexist and eventually reach a dynamic equilibrium.

Description

Technical Field

[0001] The present invention belongs to the technical field related to electrocatalysis, and more specifically, relates to an electrocatalyst and a preparation method and application thereof. Background Art

[0002] Building a sustainable global energy storage and conversion system is currently a core challenge for human survival and development. The European Clean Hydrogen Alliance believes that hydrogen plays a vital role in the energy transition: enabling large-scale, efficient consumption of renewable energy, redistributing energy across industries and regions, acting as an energy buffer to enhance energy system resilience, reducing carbon emissions in transportation and industrial energy use, replacing coke in the metallurgical industry, and reducing carbon emissions from building heating. As the clean energy with the greatest potential, hydrogen has been incorporated into energy strategies and has become a key option for optimizing energy consumption and ensuring energy supply security.

[0003] The hydrogen production process is categorized by carbon emission intensity into gray hydrogen (coal-based hydrogen), blue hydrogen (natural gas-based hydrogen), and green hydrogen (low-temperature water electrolysis and renewable energy-based hydrogen). Currently, over 95% of the world's hydrogen comes from fossil fuel reforming, a production process associated with high CO2 emissions; only approximately 4% to 5% of hydrogen comes from water electrolysis, which emits zero CO2. The original intention of developing the hydrogen energy industry was to achieve zero or low carbon emissions, so gray and blue hydrogen will gradually be replaced by green hydrogen based on renewable energy. Green hydrogen is the future direction of the energy industry.

[0004] In addition, low-temperature water electrolysis hydrogen production technology has the advantages of stable hydrogen production, high hydrogen purity, simple equipment, and relatively mature technology. It is the most promising method for large-scale hydrogen production. However, due to the slow kinetics of multi-electron catalytic reactions, especially the four-electron oxygen evolution half-reaction at the anode, the hydrogen production cost of low-temperature water electrolysis hydrogen production technology is still relatively high. For example, the energy cost of the most mature alkaline water electrolysis technology in the industry can be as high as 40% to 60%. This technology uses nickel mesh as a bifunctional catalyst. The low electrocatalytic oxygen evolution activity of nickel mesh is one of the key factors restricting energy costs. Efficient oxygen evolution electrocatalysts can significantly accelerate the overall water decomposition reaction kinetics, reduce the voltage of the electrolytic water tank, thereby improving energy utilization efficiency and saving hydrogen production energy costs.

[0005] With the exploration of many pioneering scholars in materials chemistry, the field of electrocatalysis has made great progress. However, the current electrocatalytic oxygen evolution materials still have the problem of low current density (100mA cm -2Key challenges include low catalytic activity, low yield, poor stability, and complex preparation processes that prevent scalability. Cheap transition metal nickel-iron oxides / hydroxides, due to their unique surface electronic structure, possess suitable bonding strength to oxygen-containing intermediates involved in the oxygen evolution reaction (OER), demonstrating relatively ideal catalytic performance. However, the in situ precipitation of metal sites within the catalyst during the OER poses a significant challenge to the catalytic stability of these materials. Summary of the Invention

[0006] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides an electrocatalyst and its preparation method and application. The preparation method can regulate the doping of Co and S, and the obtained catalyst has high electrocatalytic oxygen evolution activity and stability. The preparation method is simple, mild and easy to scale up.

[0007] To achieve the above object, according to one aspect of the present invention, a method for preparing an electrocatalyst is provided, the method comprising the following steps:

[0008] The electrocatalyst is obtained by contacting and reacting the etching solution with the nickel substrate.

[0009] Furthermore, the etching solution contains a solution of ferric chloride, cobalt chloride and sodium thiosulfate.

[0010] Furthermore, ferric chloride, cobalt chloride and sodium thiosulfate are mixed with deionized water, stirred and then allowed to stand to obtain a corrosion solution.

[0011] Furthermore, the concentration of the ferric chloride is 1 to 30 mmol, the concentration of the cobalt chloride is 1 to 30 mmol, the concentration of the sodium thiosulfate is 1 to 30 mmol, and the volume of the deionized water is not less than 100 mL.

[0012] Furthermore, the contact and reaction between the etching solution and the nickel substrate is carried out under normal pressure, wherein the etching solution is heated and stabilized at the reaction temperature, and then the nickel substrate is immersed in the etching solution for reaction.

[0013] Furthermore, the heating method is water bath heating, the reaction temperature is 40-100° C., and the reaction time is 1 min-12 h.

[0014] Furthermore, after the reaction is completed, the corrosion solution on the surface of the nickel substrate is cleaned and dried to obtain the electrocatalyst. The cleaning solution used is deionized water, and the cleaning method is to rinse with deionized water for 3 to 5 times.

[0015] Furthermore, the foamed Ni or Ni mesh substrate is cut and then washed with anhydrous ethanol and deionized water to obtain the nickel substrate.

[0016] The present invention provides an electrocatalyst, which is prepared by the above-mentioned method for preparing the electrocatalyst.

[0017] The present invention also provides a use of the catalyst described above in electrocatalytic hydrogen production.

[0018] In general, the above technical solutions conceived by the present invention, compared with the prior art, the electrocatalyst provided by the present invention and its preparation method and application have the following beneficial effects:

[0019] 1. Using a solution containing ferric chloride, cobalt chloride and sodium thiosulfate as a corrosion solution can produce Ni-containing 2+ 、Fe 2+ 、Co 2+ OH - 、S 2- microenvironment. Specifically, S2O4 2- and Cl - Coexistence will cause pitting corrosion of the Ni substrate and release Ni 2+ ;S2O4 2- The redox and weak alkalinity can release S 2- and OH - ; Controlling the ratio of Fe and Co in the corrosion solution can regulate the Co 2+ Due to the relatively small solubility constant of the precipitates obtained from the aforementioned metal ions and anions, pitting and precipitation reactions coexist and ultimately reach a dynamic equilibrium. Furthermore, due to the anisotropic growth behavior during the self-assembly of layered materials, the precipitated products tend to grow vertically into ultrathin nanosheets.

[0020] 2. By controlling the corrosion solution and reaction temperature, the controllable preparation of Co and S co-modified ultrathin NiFe LDH nanosheet arrays (labeled as Co / S-NiFe LDH) can be achieved, thereby optimizing their electrocatalytic oxygen evolution performance; the obtained Co / S-NiFe LDH catalyst has high electrocatalytic oxygen evolution activity and stability, and the preparation method is simple, mild, and easy to scale up.

[0021] 3. The catalyst prepared by the present invention has good structural stability during the electrolysis of water for oxygen evolution, which is specifically manifested as follows: 1) The catalyst involved in the present invention has an ultra-thin nanosheet structure, which can reduce the lattice dissolution effect caused by the migration and accumulation of OH- between layers; 2) The doped S atoms will precipitate in situ during the electrolysis of water, thereby forming a layer of SO x The inorganic ion membrane can inhibit the precipitation of metal sites in NiFe LDH; 3) the doped Co atoms can change the electronic structure of Ni\Fe, thereby increasing the coordination ability (bond energy) of Ni / Fe with the surrounding oxygen atoms, thereby further improving the stability of the catalyst.

[0022] 4. The preparation method can grow ultrathin Co and S co-doped NiFe LDH nanosheet arrays onto a Ni substrate through a simple thermal corrosion reaction for about 30 minutes at normal pressure and near room temperature. The resulting nanosheet array is very uniform and dense, with excellent mechanical and fatigue resistance. The nanosheets grow perpendicular to the substrate and have an average thickness of only 1.2 nm, providing an ultra-high specific surface area and abundant active sites.

[0023] 5. The catalyst has excellent electrocatalytic oxygen evolution performance under alkaline conditions, requiring only 220, 300, and 320 mV overpotentials to drive 10, 500, and 1000 mA cm -2 The current density can be stably operated for more than 2000h.

[0024] 6. The preparation method of this catalyst is simple, the raw materials are cheap, the process is green and economical, and it is easy to prepare on a large scale, and has industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the Co / S-NiFe LDH nanosheet prepared by the present invention. It can be seen that the Co / S-NiFe LDH material has a clear sheet structure;

[0026] Figure 2 (a) and (b) are transmission electron microscope images of the Co / S-NiFe LDH nanosheets prepared by the present invention. The morphological characteristics of each sample are observed at different magnifications. It can be seen that the Co / S-NiFe LDH2 nanosheet has a flat two-dimensional plane and a wrinkled surface;

[0027] Figure 3 The X-ray powder diffraction spectrum of the Co / S-NiFe LDH nanosheets prepared by the present invention and the corresponding standard card pattern;

[0028] Figure 4 Raman spectrum of Co / S-NiFe LDH nanosheets prepared in the present invention;

[0029] Figure 5 This is the EDS surface scanning spectrum of the Co / S-NiFe LDH nanosheets prepared in the present invention, in which the content ratio of Fe, Co, Ni, and S elements distributed on the surface is approximately 20:1:11:68;

[0030] Figure 6 This is the linear voltammetric scanning curve of the wrinkled Co / S-NiFe LDH nanosheet prepared by the present invention before and after compensation. After compensation, only 1.90V overpotential is required to provide 2000mA cm -2The catalytic oxygen production current density;

[0031] Figure 7 This is the uncompensated chronoamperometric time curve of the wrinkled Co / S-NiFe LDH nanosheet prepared in the present invention, at 400 mA cm -2 The catalyst can operate stably for more than 2000h at a high current density;

[0032] Figure 8 The scanning electron microscope images of the Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different reaction temperatures and times) of the present invention are shown. The reaction temperature is 70°C and the reaction time is 1 min, 5 min, 30 min and 60 min respectively, corresponding to Figure 8 (a), (b), (c), (d); the samples with reaction temperatures of 40℃ and 90℃ were reacted for 12h and 10min, respectively, corresponding to Figure 8 (e) and (f) in the

[0033] Figure 9 The Raman spectra of the Co / S-NiFe LDH nanosheets prepared under different experimental parameters of the present invention were obtained at a reaction temperature of 70°C for 1 min, 5 min, 30 min and 60 min respectively;

[0034] Figure 10 a and b are the electrocatalytic hydrogen production performance diagrams of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different reaction temperatures and times) of the present invention;

[0035] Figure 11 Scanning electron micrographs of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different S contents involved in the reaction) of the present invention; (a) is 10mM Co + 20mM Fe, (b) is 10mM S + 10mM Co + 20mM Fe, and (c) is 20mM S + 10mM Co + 20mM Fe. The addition of S makes the array of nanosheets more uniform.

[0036] Figure 12 The Raman spectra of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different S contents involved in the reaction) of the present invention are shown;

[0037] Figure 13 The electrocatalytic hydrogen production performance of Co / S-NiFe LDH nanosheets prepared by the present invention under different experimental parameters (different S contents participating in the reaction);

[0038] Figure 14Scanning electron micrographs of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different Fe contents involved in the reaction) of the present invention; wherein (a) is 20 mM S, (b) is 20 mM S+10 mM Fe, and (c) is 20 mM S+20 mMFe;

[0039] Figure 15 Raman spectra of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different Fe contents involved in the reaction) and the control sample (20mM S+10mM Co+20mM Fe, 70°C, 30min);

[0040] Figure 16 The electrocatalytic hydrogen production performance of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different Fe contents involved in the reaction) and the control sample (20mM S+10mM Co+20mM Fe, 70°C, 30min) of the present invention is shown. The addition of Fe can further improve the performance of the catalyst.

[0041] Figure 17 Scanning electron micrographs of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different Co contents involved in the reaction) of the present invention; wherein (a) is 20mM S+20mM Fe, (b) is 20mM S+10mM Co+10mM Fe, and (c) is 20mM S+20mM Co+20mM Fe;

[0042] Figure 18 The Raman spectra of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different Co contents involved in the reaction) of the present invention are shown;

[0043] Figure 19 The electrocatalytic hydrogen production performance of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different Co contents in the reaction) of the present invention can be improved by further controlling the Co content in the reactants.

[0044] Figure 20 Scanning electron microscope images of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different material substrates) of the present invention; (a) is a nanosheet prepared on a nickel foam substrate, and (b) is a nanosheet prepared on a nickel mesh substrate;

[0045] Figure 21 The Raman spectra of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different material substrates) of the present invention;

[0046] Figure 22 This is a graph showing the electrocatalytic hydrogen production performance of Co / S-NiFe LDH nanosheets prepared under different experimental parameters (different material substrates) in the present invention. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0048] While making full use of the unique surface chemical adsorption properties of nickel iron oxide / hydroxide, the precipitation behavior of metal sites in the NiFeLDH catalyst can be adjusted to design and develop new electrocatalytic oxygen evolution materials based on nickel iron oxide / hydroxide that are efficient, durable, safe, controllable, low-cost, and oriented towards industrial applications.

[0049] Based on this, the present invention provides a method for preparing an electrocatalyst, comprising the following steps: contacting and reacting a nickel substrate with an etching solution to obtain an electrocatalyst, wherein the electrocatalyst is a Co- and S-co-doped NiFeLDH electrocatalyst having a microstructure comprising an array of nanosheets approximately 1.5 nm thick. The etching solution comprises a solution of ferric chloride, cobalt chloride, and sodium thiosulfate.

[0050] Specifically, the corrosion solution is brought into contact with and reacts with the Ni substrate. After the reaction is completed, the corrosion solution on the surface of the substrate is cleaned off and dried to obtain a Co / S-NiFe LDH electrocatalyst.

[0051] During the reaction, due to the presence of the corrosive solution, Ni-containing 2+ 、Fe 2+ 、Co 2+ OH - 、S 2- microenvironment. Specifically, S2O4 2- and Cl - Coexistence will cause pitting corrosion of the Ni substrate and release Ni 2+ ;S2O4 2- The redox and weak alkalinity can release S 2- and OH - ; Controlling the ratio of Fe and Co in the corrosion solution can regulate the Co 2+Due to the small solubility constant of the precipitates obtained from the aforementioned metal ions and anions, pitting and precipitation reactions coexist and ultimately reach a dynamic equilibrium. Furthermore, due to the anisotropic growth behavior during the self-assembly of layered materials, the precipitated products tend to grow vertically into ultrathin nanosheets. Based on these characteristics, the amount of cobalt and sulfur modified in the Fe-Co-Ni electrocatalyst can be regulated by controlling the corrosion solution and reaction temperature, thereby optimizing its electrocatalytic oxygen evolution performance.

[0052] The Co / S-NiFe LDH electrocatalyst prepared by the present invention has a unique surface electronic structure and nanosheet array structure, which provides active sites and mass transfer channels for electrocatalytic oxygen evolution, ultimately improving reaction activity and stability. The reaction conditions in the preparation method are relatively mild and easy to control. The catalyst synthesis raw materials and equipment costs are low, the process is simple, and it is easy to scale up, which has broad industrial application prospects.

[0053] In this embodiment, the etching solution is prepared from deionized water and a solute, wherein the solute includes ferric chloride, cobalt chloride and sodium thiosulfate. The Ni substrate is selected from one of foamed Ni and Ni mesh.

[0054] The etching solution is brought into contact with and reacts with the Ni substrate by immersing the substrate in the etching solution at normal pressure or near room temperature. The Ni substrate soaked in the etching solution is rinsed with deionized water and air-dried.

[0055] The etching solution is prepared as follows: deionized water is used as the solvent, a certain mass of solute is weighed and added to the deionized water, and the solution is stirred uniformly using a magnetic stirrer; the concentration of the solute in the deionized water is 1 to 30 mmol; and the volume of the deionized water is greater than 100 mL. In this embodiment, the concentration of the ferric chloride is 1 to 30 mmol, the concentration of the cobalt chloride is 1 to 30 mmol, and the concentration of the sodium thiosulfate is 1 to 30 mmol.

[0056] When the corrosion solution contacts and reacts with the Ni substrate, the area of ​​the Ni substrate is greater than 1 cm 2 When the etching solution contacts and reacts with the Ni substrate, the reaction time is 1 minute to 12 hours, the reaction temperature is 40 to 100 degrees Celsius, and the heating method is water bath heating. When the etching solution contacts and reacts with the Ni substrate, the etching solution is heated to the preset reaction temperature and the Ni substrate is placed in the etching solution.

[0057] The preparation method of the Ni substrate is specifically as follows:

[0058] Cut the Ni foam or Ni mesh substrate and clean it with anhydrous ethanol and deionized water. The area of ​​the Ni foam or Ni mesh substrate cut is 1 cm 2 ~0.5m2 The cleaning step is to soak the substrate in anhydrous ethanol and deionized water for ultrasonic cleaning for 5 minutes.

[0059] In one embodiment, the cleaning solution for the Ni substrate after the reaction is deionized water, and the cleaning method is to rinse with deionized water for 3 to 5 times.

[0060] The present invention also provides an electrocatalyst prepared by the above-mentioned method for preparing the electrocatalyst, wherein the electrocatalyst is used for electrocatalytic hydrogen production.

[0061] The present invention is further described in detail below with reference to several embodiments.

[0062] Example 1

[0063] Accurately weigh 4.98g of sodium thiosulfate, 3.98g of ferric chloride, and 2.37g of cobalt chloride, add them to 200mL of deionized water, and stir and dissolve with a magnetic stirrer; place the obtained clarified corrosion solution in a water bath, heat it to 70°C and stabilize it for 10 minutes; cut a 1cm×3cm piece of foamed Ni substrate, soak it in 20mL of anhydrous ethanol and deionized water for ultrasonic cleaning for 5 minutes respectively; soak the cleaned foamed Ni substrate in the corrosion solution after the temperature is stabilized for reaction for 30 minutes. The silver-gray foamed Ni substrate turns black and is taken out to obtain the target Co / S-NiFe LDH electrocatalyst.

[0064] The Co / S-NiFe LDH electrocatalyst prepared in this embodiment was observed using a scanning electron microscope. Figure 1 As shown, the Co / S-NiFe LDH electrocatalyst exhibits a three-dimensional hierarchical structure. A uniform and dense array of nanosheets grows on the originally smooth Ni foam substrate, with clearly visible raised edges, indicating vertical growth. This in-situ vertical growth of the nanosheets not only connects the three-dimensional conductive Ni foam and the nanosheets through strong chemical bonds, but also facilitates electron transport between atomic layers and the diffusion of electrolyte liquid and bubbles between the nanosheet layers, providing excellent mechanical properties and mass transfer conditions for the catalytic process.

[0065] Further higher resolution transmission electron microscopy was used to observe the single nanosheets released by ultrasound, as shown in the attached figure. Figure 2 As shown, the lateral size of the nanosheet is about 500nm, and the low contrast of the sheet indicates that it is an ultra-thin structure. Specifically, further magnification and observation of the rolled-up edge of the nanosheet show that its thickness is about 1.15nm. The ultra-thin sheet structure provides abundant active sites and can reduce OH - Lattice dissolution effect caused by interlayer migration and accumulation. Figure 3The X-ray powder diffraction pattern of the Co / S-NiFe LDH electrocatalyst prepared in this example corresponds to Ni(OH)2, and the PDF card number is 038-0715. Figure 2 The 0.253nm lattice fringes extracted from Figure 4 The above characterization of the crystal structure shows that the original crystal structure is well maintained after cobalt and sulfur doping. Figure 5 As shown, the element distribution in the sample was further characterized by element mapping, and it can be observed that S, Fe, Co, and Ni are evenly distributed, with a ratio of approximately 20:1:11:68.

[0066] To verify the electrocatalytic oxygen evolution performance of the target Co / S-NiFe LDH electrocatalyst of this example, a 1 cm × 1.5 cm section was cut and secured to a platinum electrode holder with sealing adhesive, exposing a 1 cm × 1 cm active area. This served as the working electrode. A three-electrode system consisting of the working electrode, a saturated Ag / AgCl reference electrode, and a graphite rod counter electrode was constructed. Electrochemical performance was tested in a 1.0 M KOH solution using an Autolab PGSTAT 302N electrochemical workstation as a DC power supply. Figure 6 The linear sweep voltammetric curves of the target Fe-Co-Ni electrocatalyst before and after compensation are shown. The solution impedance is approximately 0.77Ω. The target catalyst has excellent catalytic performance and can provide 2000mA cm at a potential of only 1.90V after compensation. -2 The catalytic oxygen production current density. Figure 7 The uncompensated chronoamperometry curve shows that the solution impedance is approximately 1.45Ω at 400 mA cm -2 The catalyst can operate stably for more than 2000 hours at a high current density and has excellent fatigue resistance and mechanical stability.

[0067] Example 2 (Time)

[0068] Accurately weigh six groups of 4.98g sodium thiosulfate, 3.98g ferric chloride, and 2.37g cobalt chloride, add them to 200mL deionized water, and stir and dissolve with a magnetic stirrer; place the clarified corrosion solutions obtained from four of the groups in a water bath, heat them to 70°C and stabilize for 10 minutes, and heat the other two groups to 40°C and 90°C, respectively; cut five 1cm×3cm foam Ni substrates, soak them in 20mL anhydrous ethanol and deionized water for ultrasonic cleaning for 5 minutes, respectively; soak the washed foam Ni substrate in the corrosion solution stabilized at 70°C for 1min, 5min, 30min and 60min, respectively, and react in the corrosion solution of 40°C and 90°C for 12h and 10min, respectively. The silver-gray foam Ni substrate turns black and is taken out to obtain the target Co / S-NiFe LDH electrocatalyst.

[0069] First, as Figure 8 The scanning electron microscope shown in the figure shows that all six samples have grown nanosheets with vertical growth structure, but it can be seen that the sizes of the nanosheets obtained with different reaction times are also different. Figure 9 The Raman spectra shown show that samples with reaction times of 5, 30, and 60 minutes all show signal peaks corresponding to Ni-OH and Ni-O, while the sample with a reaction time of 1 minute shows no signal peaks. The scanning electron microscopy and Raman spectroscopy data demonstrate that reaction time plays a significant role in sample synthesis, with the length of reaction time having a positive correlation with the sample's synthesis.

[0070] To verify the electrocatalytic oxygen evolution performance of the Co / S-NiFe LDH electrocatalyst of this example, a 1 cm × 1.5 cm section was cut and secured to a platinum electrode holder with sealing adhesive, exposing a 1 cm × 1 cm active area. This served as the working electrode. A three-electrode system consisting of the working electrode, a saturated Ag / AgCl reference electrode, and a graphite rod counter electrode was constructed. Electrochemical performance was tested in a 1.0 M KOH solution using a Chenhua CHI660e electrochemical workstation as a DC power source. Figure 10 This is the linear sweep voltammetry curve of the target Fe-Co-Ni electrocatalyst before compensation. The solution impedance is about 1.5Ω. The four samples prepared at different reaction times have certain catalytic performance. The four samples with reaction times of 1min, 5min, 30min and 60min can provide 100mA cm at overpotentials of 409, 392, 381 and 390mV respectively. -2 The catalytic oxygen production current density is 100mA cm at 389, 381 and 420mV overpotential respectively. -2 The catalytic oxygen production current density is 1.33 Å. It can be seen that the reaction temperature has an impact on the catalytic performance of the catalyst, and the catalytic performance can be improved by prolonging the reaction time.

[0071] Example 3(S)

[0072] Accurately weigh (1) 3.98 g ferric chloride and 2.37 g cobalt chloride; (2) 2.49 g sodium thiosulfate, 3.98 g ferric chloride, and 2.37 g cobalt chloride; (3) 4.98 g sodium thiosulfate, 3.98 g ferric chloride, and 2.37 g cobalt chloride, and add them to 200 mL deionized water respectively, and stir and dissolve them with a magnetic stirrer; place the obtained clear corrosion solution in a water bath, heat it to 70°C and stabilize it for 10 minutes; cut a 1 cm × 3 cm piece of foamed Ni substrate, and soak it in 20 mL anhydrous ethanol and deionized water for ultrasonic cleaning for 5 minutes respectively; soak the washed foamed Ni substrate in the three sets of corrosion solutions after temperature stabilization for reaction for 30 minutes, and the silver-gray foamed Ni substrate turns black, which is taken out and is the target Co / S-NiFe LDH electrocatalyst.

[0073] like Figure 11 As shown in Figure 2, under a scanning electron microscope, it can be observed that the three groups of samples have grown nanosheets with vertical growth structures on the nickel foam skeleton. However, it can be seen that the sizes of the obtained nanosheets are different depending on the different amounts of sodium thiosulfate added. Figure 12 In the Raman spectra shown, signal peaks of Ni-OH and Ni-O appeared in all three samples, but the signal peak in the sample without S was shifted relative to the other two samples.

[0074] To verify the electrocatalytic oxygen evolution performance of the Co / S-NiFe LDH electrocatalyst of this example, a 1 cm × 1.5 cm section was cut and secured to a platinum electrode holder with sealing adhesive, exposing a 1 cm × 1 cm active area. This served as the working electrode. A three-electrode system consisting of the working electrode, a saturated Ag / AgCl reference electrode, and a graphite rod counter electrode was constructed. Electrochemical performance was tested in a 1.0 M KOH solution using a Chenhua CHI660e electrochemical workstation as a DC power source. Figure 13 This is the linear sweep voltammetry curve of the target Co / S-NiFe LDH electrocatalyst before compensation. The solution impedance is about 1.5Ω. The three samples prepared by adding different amounts of sodium thiosulfate all have certain catalytic performance.

[0075] In this example, it is not difficult to find that the addition of S in the reaction has a certain effect on the morphology and growth of the catalyst, which is conducive to the growth of nanosheets into arrays, but has little effect on the performance.

[0076] Example 4 (Fe)

[0077] Accurately weigh (1) 4.98 g of sodium thiosulfate; (2) 4.98 g of sodium thiosulfate and 1.98 g of ferric chloride; (3) 4.98 g of sodium thiosulfate and 3.98 g of ferric chloride, respectively, add them into 200 mL of deionized water, and stir and dissolve them with a magnetic stirrer; place the obtained clear corrosion solution in a water bath, heat it to 70°C and stabilize it for 10 minutes; cut a 1 cm × 3 cm piece of foamed Ni substrate, soak it in 20 mL of anhydrous ethanol and deionized water for ultrasonic cleaning for 5 minutes respectively; soak the cleaned foamed Ni substrate in the corrosion solution after temperature stabilization for reaction for 30 minutes, and the silver-gray foamed Ni substrate turns black, which is taken out and is the target Co / S-NiFe LDH electrocatalyst.

[0078] Figure 14 Scanning electron microscopy in the three samples showed that vertically grown nanosheets were grown on the smooth nickel foam surface. The two samples prepared showed vertical growth in the Raman spectrum ( Figure 15 ), the higher the Fe content, the stronger the signal peaks of Ni-OH and Ni-O that appear. At the same time, the addition of Fe will affect the shift of the peak position. It can be seen that the Fe content during the reaction will affect the synthesis of the catalyst. In order to verify the electrocatalytic oxygen evolution performance of the Co / S-NiFe LDH electrocatalyst of this embodiment, it was cut into 1cm×1.5cm, fixed on a platinum electrode clip with sealing glue and exposing a 1cm×1cm effective area to serve as a working electrode. The working electrode, saturated Ag / AgCl reference electrode and graphite rod counter electrode constitute a three-electrode system, and the electrochemical performance test was carried out in 1.0M KOH solution using Chenhua CHI660e electrochemical workstation as a DC power supply. Figure 16 This is the linear sweep voltammetry curve before catalyst compensation, and the solution impedance is about 1.5Ω. The three samples prepared by different contents of FeCl2 have different catalytic performances. The sample without FeCl2 provides 100mA cm at 466mV overpotential. -2 The other two groups of samples with Fe participating in the reaction can provide 100 mA cm at an overpotential of 395 mV. -2 The catalytic oxygen production current density is as high as 1.5 wt%. With the addition of Fe, the electrocatalytic performance of the catalyst is improved.

[0079] This example is easy to understand. By adding Fe for regulation, the electrocatalytic performance of the catalyst can be improved to a certain extent.

[0080] Example 5 (Co)

[0081] Accurately weigh (1) 0.5 g ferric chloride, 0.5 g cobalt chloride, and 0.5 g sodium thiosulfate; (2) 0.5 g ferric chloride, 0.5 g cobalt chloride, and 0.5 g sodium thiosulfate; (3) 0.5 g ferric chloride, 0.5 g cobalt chloride, and 0.5 g sodium thiosulfate, and add them to 200 mL deionized water respectively, and stir and dissolve them with a magnetic stirrer; place the obtained clear corrosion solution in a water bath, heat it to 70°C and stabilize it for 10 minutes; cut a 1 cm × 3 cm foam Ni substrate, and soak it in 20 mL anhydrous ethanol and deionized water for ultrasonic cleaning for 5 minutes respectively; soak the cleaned foam Ni substrate in the three groups of temperature-stabilized corrosion solutions for reaction for 30 minutes, and the silver-gray foam Ni substrate turns black, which is taken out to obtain the target Co / S-NiFe LDH electrocatalyst.

[0082] like Figure 17 Scanning electron microscopy images show that vertically grown nanosheets were obtained in all three groups of samples. Figure 18 In the Raman spectra shown, all three samples showed signal peaks of Ni-OH and Ni-O, but it can be seen that the signal peak of the sample with 10mM CoCl2 added is the strongest, and the signal peaks of the samples with 20mM CoCl2 added and without CoCl2 are slightly weaker, which shows that the addition of Co has an important influence on the synthesis of nanosheet samples.

[0083] To verify the electrocatalytic oxygen evolution performance of the Co / S-NiFe LDH electrocatalyst of this example, a 1 cm × 1.5 cm section was cut and secured to a platinum electrode holder with sealing adhesive, exposing a 1 cm × 1 cm active area. This served as the working electrode. A three-electrode system consisting of the working electrode, a saturated Ag / AgCl reference electrode, and a graphite rod counter electrode was constructed. Electrochemical performance was tested in a 1.0 M KOH solution using a Chenhua CHI660e electrochemical workstation as a DC power source. Figure 19 The linear sweep voltammetry curve of the target Fe-Co-Ni electrocatalyst before compensation is shown in Figure 2. The solution impedance is approximately 1.5Ω. The three samples prepared by adding different amounts of CoCl2 have certain catalytic performance, providing 100mA cm at overpotentials of 395, 381, and 402mV, respectively. -2 The catalytic oxygen production current density is as follows: with the addition of Co element, the performance of the catalyst prepared when the reactant concentration is 10mM is the best.

[0084] By controlling the Co content in the reactants, the electrocatalytic performance can be further improved.

[0085] Example 6

[0086] Accurately weigh two groups of 4.98g sodium thiosulfate, 3.98g ferric chloride, and 2.37g cobalt chloride, add them respectively to 200mL deionized water, and stir and dissolve with a magnetic stirrer; place the obtained clarified corrosion solution in a water bath, heat it to 70℃ and stabilize it for 10min; cut a 1cm×3cm piece of foam Ni and nickel mesh substrate, soak them in 20mL anhydrous ethanol and deionized water for ultrasonic cleaning for 5min respectively; soak the cleaned foam Ni and nickel mesh substrate in the corrosion solution after temperature stabilization for 30min, and the silver-gray substrate turns black, which is taken out to obtain the target Co / S-NiFe LDH electrocatalyst.

[0087] like Figure 20 Scanning electron microscopy showed that both groups of samples obtained vertically grown nanosheets. Figure 21 In the Raman spectra shown, both samples showed Ni-OH and Ni-O signal peaks.

[0088] To verify the electrocatalytic oxygen evolution performance of the Co / S-NiFe LDH electrocatalyst of this example, a 1 cm × 1.5 cm square was cut and secured to a platinum electrode holder with sealing adhesive, exposing a 1 cm × 1 cm active area. This served as the working electrode. A three-electrode system consisting of the two working electrodes, a saturated Ag / AgCl reference electrode, and a graphite rod counter electrode was constructed. Electrochemical performance was tested in 1.0 M KOH solution using an Autolab PGSTAT 302N electrochemical workstation as a DC power supply. Figure 22 The linear sweep voltammetry curve of the target Co / S-NiFe LDH electrocatalyst before compensation is about 0.77Ω. The two samples prepared with foamed Ni and nickel mesh as substrates have certain catalytic performance, providing 100mA cm at an overpotential of 364mV and 406mV, respectively. -2 The catalytic oxygen production current density.

[0089] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an electrocatalyst, characterized in that: The method comprises the following steps: The electrocatalyst is obtained by contacting and reacting the etching solution with the nickel substrate; The etching solution is composed of a solution of ferric chloride, cobalt chloride and sodium thiosulfate, wherein the concentration of the ferric chloride is 1 to 30 mmol, the concentration of the cobalt chloride is 1 to 30 mmol, the concentration of the sodium thiosulfate is 1 to 30 mmol, and the volume of the deionized water solvent is 100 mL to 200 mL. The etching solution is contacted and reacted with the nickel substrate by heating the etching solution under normal pressure, stabilizing it at a reaction temperature, and then immersing the nickel substrate in the etching solution for reaction. The heating method is water bath heating, the reaction temperature is 40 to 100°C, and the reaction time is 1 minute to 12 hours.

2. The method for preparing an electrocatalyst according to claim 1, wherein: Ferric chloride, cobalt chloride and sodium thiosulfate are mixed with deionized water, stirred and allowed to stand to obtain a corrosion solution.

3. The method for preparing an electrocatalyst according to claim 1, wherein: After the reaction is completed, the corrosion solution on the surface of the nickel substrate is cleaned and dried to obtain the electrocatalyst. The cleaning solution used is deionized water, and the cleaning method is to rinse with deionized water 3 to 5 times.

4. The method for preparing the electrocatalyst according to any one of claims 1 to 2, wherein: The foamed Ni or Ni mesh substrate is cut and then washed with anhydrous ethanol and deionized water to obtain the nickel substrate.

5. An electrocatalyst, characterized in that: The electrocatalyst is prepared by the method for preparing the electrocatalyst according to any one of claims 1 to 4.

6. Use of the catalyst according to claim 5 in electrocatalytic hydrogen production.

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