Preparation method of FeOOH (at) V-CoP composite catalyst

Abstract

The invention relates to the technical field of electrochemical catalysis, and discloses a preparation method of a FeOOH (at) V-CoP composite catalyst, which comprises the following steps: S10, pretreatment of NF: cutting the NF into 3.0 cm * 2.0 cm rectangular sheets, putting the NF into a 3.0 M hydrochloric acid solution, carrying out ultrasonic treatment for 20 minutes, then sequentially carrying out ultrasonic treatment in acetone, ethanol and deionized water for 10 minutes, putting the cleaned NF into a vacuum oven of 60 DEG C, and drying to obtain the FeOOH (at) V-CoP composite catalyst. Preparing for later use; and S20, loading and reacting a V-Co precursor, preparing a V-Co precursor solution containing Co (NO3) 2.5 H2O, NH4VO3, urea and NH4F, fully stirring and mixing, immersing the pretreated NF into the V-Co precursor solution, and transferring the V-Co precursor solution into an autoclave. The prepared FeOOH-coated V-CoP / NF composite catalyst not only has excellent catalytic activity, but also shows good stability and long-term use performance, and provides powerful support for industrial application of a water electrolysis hydrogen production and oxygen production technology.

Description

Technical Field

[0001] The invention relates to the technical field of electrochemical catalysis, and in particular to a method for preparing a FeOOH@V-CoP composite catalyst. Background Art

[0002] With the continuous growth of global energy demand and the increasing awareness of environmental protection, the development of efficient and clean energy conversion and storage technologies has become an important research direction in the current scientific and technological field. Hydrogen, as a high-energy-density, zero-emission clean energy, is considered to be an important part of the future energy system. As an efficient and environmentally friendly method for hydrogen preparation, water electrolysis is the core of improving the energy conversion efficiency and reducing the system cost during the electrolysis process. In this context, the performance optimization of electrocatalysts is particularly important.

[0003] In the field of hydrogen production by water electrolysis, precious metals such as iridium and platinum have long been in a dominant position due to their excellent catalytic activity, becoming key electrocatalysts to promote the efficient electrolysis of water. However, with the rapid expansion of global demand for clean energy, the scarcity and high cost of precious metal resources have become increasingly prominent, becoming a major obstacle to the large-scale industrial application of water electrolysis hydrogen production technology. The limited resources of precious metals have led to their rising prices, which has seriously restricted the economic feasibility and market competitiveness of water electrolysis hydrogen production technology. Faced with this challenge, the scientific research community has actively engaged in the research of finding alternative materials to precious metals in order to develop new electrocatalysts with high efficiency and low cost. Transition metal-based electrocatalysts, especially cobalt phosphide (CoP), stand out due to their low cost, wide source of elements and relatively good catalytic performance, and have become a strong competitor to precious metal catalysts. CoP It not only inherits the cost advantage of transition metal-based catalysts, but also shows a certain catalytic activity in water electrolysis, providing new possibilities for water electrolysis hydrogen production technology. However, although CoP has shown positive potential in the field of water electrolysis hydrogen production, it still faces many challenges in practical applications. The primary problem is that its catalytic activity has not yet reached the ideal state, and it is difficult to meet the stringent requirements of industrial-grade water electrolysis devices for high energy conversion efficiency. This means that CoP still has a lot of room for improvement in reducing water electrolysis overpotential, increasing current density and energy conversion efficiency. In addition, the stability of CoP cannot be ignored. In the long-term water electrolysis reaction process, the CoP catalyst is easily corroded by the electrolyte solution, resulting in a gradual decline in catalytic activity and even structural damage, which seriously shortens the service life of the catalyst and increases the operation and maintenance costs of the system. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] The purpose of the present invention is to significantly improve the catalytic activity and stability of CoP by combining the dual strategies of vanadium doping and FeOOH modification to meet the industrial application needs of water electrolysis hydrogen production technology, and propose a method for preparing a FeOOH@V-CoP composite catalyst.

[0006] (II) Technical solution

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] A method for preparing a FeOOH@V-CoP composite catalyst comprises the following steps:

[0009] S10, NF pretreatment, cutting the NF into 3.0 cm × 2.0 cm rectangular pieces, placing the NF in a 3.0 M hydrochloric acid solution, ultrasonically treating for 20 min, then ultrasonically treating in acetone, ethanol and deionized water for 10 min each, placing the cleaned NF in a vacuum oven at 60 ° C to dry for later use;

[0010] S20, loading and reaction of V-Co precursor, preparing V-Co precursor solution, including Co(NO3)2·5H2O, NH4VO3, urea and NH4F, and fully stirring and mixing, immersing the pretreated NF in the V-Co precursor solution, and transferring it to an autoclave, keeping the autoclave constant temperature at 120°C for 4h, and performing a hydrothermal reaction. After the reaction, taking out the sample, washing it with ethanol and ultrapure water, and drying it in a vacuum oven at 60°C for 10h, to obtain a V-Co(OH)2 / NF intermediate;

[0011] S30, preparation of V-CoP / NF, placing V-Co(OH)2 / NF intermediate and NaH2PO2·H2O in different positions of a tube furnace, respectively, heating the tube furnace to 300°C at a heating rate of 2°C / min under argon protection, and keeping the temperature for 1h for phosphating reaction, and taking out the sample after cooling naturally to room temperature to obtain V-CoP / NF;

[0012] S40, electrodeposition and post-treatment of FeOOH layer, the V-CoP / NF sample was placed in a 0.1M FeCl2.4H2O solution as the working electrode, a voltage of 0.8V was applied relative to the saturated calomel electrode, and the electrodeposition reaction was carried out for 10 minutes. After the electrodeposition, the sample was taken out and rinsed with ultrapure water several times to remove the residual solution and the FeOOH nanoparticles that were not firmly attached. The sample was placed in a vacuum oven at 60°C and dried for 6 hours to obtain the final FeOOH@V-CoP / NF composite catalyst.

[0013] Based on the above technical solution, the present invention can also be improved as follows.

[0014] Furthermore, the step S10 specifically includes the following steps:

[0015] S101, cutting NF: Use appropriate cutting tools such as scissors, cutting machine or laser cutting machine to accurately cut NF into rectangular pieces with a size of 3.0 cm × 2.0 cm, ensuring that the cutting edges are flat and the size is accurate;

[0016] S102, oxide layer removal treatment: prepare a container and add a sufficient amount of 3.0M hydrochloric acid solution to ensure that the solution is sufficient to completely immerse the NF, carefully place the cut NF into the hydrochloric acid solution, ensure that all surfaces are in contact with the solution, place the container containing the NF and the hydrochloric acid solution in an ultrasonic cleaning machine, turn on the ultrasonic treatment function, and the treatment time is 20 minutes;

[0017] S103, deep cleaning: After cleaning, remove the NF from the hydrochloric acid solution and rinse it with deionized water to remove residual hydrochloric acid. Prepare three containers containing acetone, ethanol and deionized water respectively and arrange them in order. First, put the NF into acetone and perform ultrasonic treatment for 10 minutes. Acetone helps to remove organic pollutants. Then, take the NF out of acetone and put it into ethanol for 10 minutes of ultrasonic treatment. Ethanol is used for further cleaning and removal of residues. Finally, take the NF out of ethanol and put it into deionized water for 10 minutes of ultrasonic treatment. Deionized water is used to thoroughly rinse and remove all residual chemicals.

[0018] S104, drying treatment: take out the cleaned NF from the deionized water, use a clean nitrogen gun or natural air drying to preliminarily remove the surface moisture, place the NF in a dry and clean container, and put the container into a vacuum oven at 60°C, turn on the oven, set the temperature to 60°C, and turn on the vacuum pump to create a vacuum environment to ensure complete removal of moisture;

[0019] S105. Reserve: After drying, take the NF out of the oven and store it in a dry, dust-free environment for subsequent use. Be careful to avoid contact with pollutants to keep it clean.

[0020] Furthermore, the specific operation steps in step S20 include:

[0021] S201. Preparation of precursor solution: prepare the required chemicals, including Co(NO3)2.5H2O, NH4VO3, urea and NH4F, ensure that their purity and quality meet the experimental requirements, prepare an appropriate amount of deionized water or solvent as the basis of the solution, first add a certain amount of deionized water or solvent to a clean container, and then add Co(NO3)2.5H2O, NH4VO3, urea and NH4F to the container in sequence according to the proportion of the experimental design, and use a magnetic stirrer or a mechanical stirrer to stir and mix thoroughly until all solids are completely dissolved to form a uniform V-Co precursor solution;

[0022] S202. NF pretreatment: Use cleaning agents such as ethanol and ultrapure water to thoroughly clean the NF to remove oil, impurities and oxides on the surface. The cleaning process may need to be repeated several times to ensure the cleanliness of the NF surface. Place the cleaned NF in a dryer or use other drying methods to ensure that its surface is completely dry without residual moisture;

[0023] S203, loading and reaction: immerse the pretreated NF in the prepared V-Co precursor solution, ensure that the NF is completely immersed in the solution, and the solution can fully wet its surface. Soaking, spin coating or other appropriate methods can be used to ensure the uniform distribution of the precursor solution on the NF surface. Carefully transfer the NF loaded with the precursor solution to the autoclave, and pay attention to avoid damaging the NF or contaminating the precursor solution during the transfer process. Close the lid of the autoclave and ensure that it is well sealed. Set the temperature of the autoclave to 120°C, and turn on the heating system to keep the autoclave at this temperature for 4 hours, so that the V-Co precursor undergoes a hydrothermal reaction on the NF surface to form a V-Co(OH)2 / NF intermediate;

[0024] S204. Sample processing: After the reaction is completed, wait for the autoclave to cool down naturally to room temperature or cool down according to the safety operating procedures, open the lid of the autoclave, carefully take out the reacted NF, i.e., V-Co(OH)2 / NF intermediate, and clean the reacted sample with ethanol and ultrapure water to remove surface residues and unreacted precursors. The cleaning process may need to be repeated several times, and be careful not to damage the sample surface. Place the cleaned sample in a vacuum oven at 60°C and dry it for 10 hours to ensure that the sample will not be contaminated or damaged during the drying process.

[0025] Furthermore, the step S30 specifically includes the following steps:

[0026] S301, Preparation stage: Ensure that the V-Co(OH)2 / NF intermediate has been successfully prepared and cleaned according to the previous steps, prepare enough NaH2PO2·H2O as a phosphorus source, and confirm its purity and quality, check the integrity and cleanliness of the tube furnace and its accessories such as porcelain boats, thermocouples, etc., place the tube furnace on a stable laboratory table, and connect all necessary equipment and gas lines such as argon gas cylinders, gas flow meters, etc., to ensure that the heating system, temperature control system and gas protection system of the tube furnace are in normal working condition;

[0027] S302, sample placement: Place the V-Co(OH)2 / NF intermediate in the downstream position of the tube furnace, usually in a porcelain boat or similar container, and place NaH2PO2·H2O in the upstream position of the tube furnace to ensure that the phosphorus source can be smoothly decomposed and produce phosphating gas during the heating process;

[0028] S303, phosphating reaction: open the argon gas cylinder, adjust the gas flow meter, let the argon gas flow into the tube furnace at an appropriate flow rate, provide inert gas protection for the reaction, set the heating program of the tube furnace, start heating at a heating rate of 2°C / min, continue to pass argon during the heating process to ensure that the reaction is carried out in an inert atmosphere, monitor the temperature of the tube furnace, ensure that it is heated to 300°C according to the set program, when the temperature of the tube furnace reaches 300°C, maintain this temperature for phosphating reaction for 1 hour, continue to pass argon protection during the insulation period, and observe the reaction situation;

[0029] S304, Cooling and sampling: After the phosphating reaction is completed, turn off the heating system and let the tube furnace cool naturally to room temperature. Be careful not to rush to take out the sample to avoid damage due to a sudden drop in temperature. After the tube furnace is completely cooled, open the furnace door, take out the V-CoP / NF sample, check the appearance and integrity of the sample, and confirm whether the phosphating reaction is successful.

[0030] Furthermore, the positional relationship between the sample and the phosphorus source in step S302 should ensure that the phosphating gas can fully contact the V-Co(OH)2 / NF intermediate, and contamination and damage should be avoided when placing the sample and the phosphorus source.

[0031] Furthermore, if there are residues or impurities on the surface of the sample, it can be cleaned with ethanol, ultrapure water, etc. The cleaned sample should be placed in a dryer or dried in a vacuum oven. The dried V-CoP / NF sample should be properly stored in a dry, dust-free environment for subsequent use.

[0032] Furthermore, the step S40 specifically includes the following steps:

[0033] S401. Preparation before electrodeposition: prepare 0.1M FeCl2·4H2O solution as the electrolyte, ensure that the concentration of the solution is accurate and uniform, prepare other necessary electrodeposition equipment, such as electrodeposition tank, power supply, wire, etc., and check their working status, use V-CoP / NF sample as the working electrode, ensure that its surface is clean and free of contamination, and connect it correctly to the electrodeposition tank, select appropriate reference electrode such as saturated calomel electrode SCE and counter electrode, and connect them correctly to the electrodeposition tank;

[0034] S402, electrodeposition process: Use a power supply to apply a voltage of 0.8V to the working electrode V-CoP / NF relative to the saturated calomel electrode, keep the voltage stable, and ensure that the electrodeposition reaction can proceed smoothly. The electrodeposition reaction lasts for 10 minutes. During this period, the reaction situation should be closely monitored to ensure that the reaction proceeds as expected;

[0035] S403, post-electrodeposition treatment: After the electrodeposition is completed, the sample is immediately taken out and rinsed with ultrapure water for multiple times to remove the residual solution and FeOOH nanoparticles that are not firmly attached. The rinse should be done gently to avoid damaging the sample surface. The cleaned sample is placed in a vacuum oven at 60°C for drying for 6 hours to ensure that the sample is completely dry. The vacuum degree and temperature in the oven should be kept stable during the drying process;

[0036] S404. Final product and storage: After drying, take out the sample and check its appearance and performance to confirm that the FeOOH layer has been successfully deposited on the V-CoP / NF sample and there are no obvious defects on the sample surface. The final FeOOH@V-CoP / NF composite catalyst is properly stored in a dry and dust-free environment to avoid moisture or other contamination.

[0037] (III) Beneficial effects

[0038] Compared with the prior art, the technical solution of this application has the following beneficial technical effects:

[0039] The carefully designed pretreatment process of NF in step S10 effectively removes oxides and impurities on the NF surface, improves its surface cleanliness and hydrophilicity, and provides a good substrate for the subsequent catalyst loading. This step ensures that the V-Co precursor can be evenly and firmly loaded on the NF, laying the foundation for the subsequent formation of high-quality composite catalysts. Secondly, in step S20, the V-Co(OH)2 / NF intermediate was successfully prepared by hydrothermal reaction. By introducing vanadium element for doping, it not only adjusts the electronic structure of CoP, but also promotes the improvement of its catalytic activity. At the same time, the hydrothermal reaction method ensures the uniform distribution and good crystallization of V-Co precursor on the NF surface, providing an ideal starting material for the subsequent phosphating reaction. In step S30, the V-Co(OH)2 / NF intermediate is converted into V-CoP / NF by phosphating reaction. In this process, NaH2PO2·H2O, as a phosphorus source, reacts with V-Co(OH)2 under argon protection to generate V-CoP with excellent catalytic performance, the conditions of the phosphating reaction (such as temperature, time and atmosphere) were optimized to ensure the phase purity and crystal structure of V-CoP, thereby further improving its catalytic activity. Finally, in the S40 step, the FeOOH layer was introduced on the surface of V-CoP / NF by electrodeposition. As a highly efficient modification material, FeOOH can not only form a protective layer on the catalyst surface to improve the corrosion resistance and stability of the catalyst, but also produce a synergistic effect with V-CoP to further improve its catalytic activity. The conditions of the electrodeposition reaction (such as voltage, time and electrolyte concentration) were precisely controlled to ensure the uniformity and firmness of the FeOOH layer, thereby obtaining the final FeOOH@V-CoP / NF composite catalyst. In summary, the prepared FeOOH@V-CoP / NF composite catalyst not only has excellent catalytic activity, but also exhibits good stability and long-term performance, which provides strong support for the industrial application of water electrolysis hydrogen production and oxygen production technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a SEM picture of a catalyst in a method for preparing a FeOOH@V-CoP composite catalyst of the present invention;

[0041] Figure 2 This is a SEM picture of a catalyst in a method for preparing a FeOOH@V-CoP composite catalyst of the present invention;

[0042] Figure 3 The XRD diagrams of different catalysts in the preparation method of a FeOOH@V-CoP composite catalyst of the present invention;

[0043] Figure 4HER performance diagram of different catalysts in a method for preparing a FeOOH@V-CoP composite catalyst of the present invention;

[0044] Figure 5 This is an OER performance diagram of different catalysts in a method for preparing a FeOOH@V-CoP composite catalyst of the present invention;

[0045] Figure 6 This is a HER performance diagram of catalysts with different V doping amounts in a preparation method of a FeOOH@V-CoP composite catalyst of the present invention;

[0046] Figure 7 This is an OER performance diagram of catalysts with different V doping amounts in a method for preparing a FeOOH@V-CoP composite catalyst of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] Combination Figure 1-Figure 7 As shown, a method for preparing a FeOOH@V-CoP composite catalyst of the present invention comprises the following steps:

[0049] S10, pretreatment of nickel foam (NF), cutting the NF into rectangular pieces of 3.0 cm×2.0 cm, placing the NF in a 3.0 M hydrochloric acid solution, ultrasonically treating for 20 min, then ultrasonically treating in acetone, ethanol and deionized water for 10 min each, and drying the cleaned NF in a vacuum oven at 60° C. for later use;

[0050] Step S10 specifically includes the following steps:

[0051] S101, cutting NF: Use appropriate cutting tools such as scissors, cutting machine or laser cutting machine to accurately cut NF into rectangular pieces with a size of 3.0 cm × 2.0 cm, ensuring that the cutting edges are flat and the size is accurate;

[0052] S102, oxide layer removal treatment: prepare a container and add a sufficient amount of 3.0M hydrochloric acid solution to ensure that the solution is sufficient to completely immerse the NF, carefully place the cut NF into the hydrochloric acid solution, ensure that all surfaces are in contact with the solution, place the container containing the NF and the hydrochloric acid solution in an ultrasonic cleaning machine, turn on the ultrasonic treatment function, and the treatment time is 20 minutes;

[0053] S103, deep cleaning: After cleaning, remove the NF from the hydrochloric acid solution and rinse it with deionized water to remove residual hydrochloric acid. Prepare three containers containing acetone, ethanol and deionized water respectively and arrange them in order. First, put the NF into acetone and perform ultrasonic treatment for 10 minutes. Acetone helps to remove organic pollutants. Then, take the NF out of acetone and put it into ethanol for 10 minutes of ultrasonic treatment. Ethanol is used for further cleaning and removal of residues. Finally, take the NF out of ethanol and put it into deionized water for 10 minutes of ultrasonic treatment. Deionized water is used to thoroughly rinse and remove all residual chemicals.

[0054] S104, drying treatment: take out the cleaned NF from the deionized water, use a clean nitrogen gun or natural air drying to preliminarily remove the surface moisture, place the NF in a dry and clean container, and put the container into a vacuum oven at 60°C, turn on the oven, set the temperature to 60°C, and turn on the vacuum pump to create a vacuum environment to ensure complete removal of moisture;

[0055] S105, standby: After drying, take the NF out of the oven and store it in a dry, dust-free environment for subsequent use. Be careful to avoid contact with pollutants to keep it clean.

[0056] Precise cutting tools and methods ensure that the nickel foam (NF) sheets have consistent size and smooth cutting edges, which is conducive to the uniform loading and stable attachment of the subsequent catalyst. Secondly, ultrasonic cleaning and 3.0M hydrochloric acid solution are used in the deoxidation layer treatment step to effectively remove oxides and other impurities on the NF surface, improve its surface activity and hydrophilicity, and provide better substrate conditions for catalyst loading. In the deep cleaning step, acetone, ethanol and deionized water are used for ultrasonic treatment in sequence to further remove organic pollutants, residues and chemicals on the NF surface, ensuring the ultimate cleanliness of the substrate. The drying step is carried out in a vacuum oven, which not only removes all residual moisture, but also avoids the oxidation of NF at high temperature, ensuring the stability and quality of the substrate. Finally, the storage environment control in the standby step avoids the contact of NF with pollutants and maintains its long-term clean state, laying a solid foundation for the subsequent catalyst preparation work. These meticulous operation steps jointly improve the preparation quality of the NF substrate, which in turn helps to improve the catalytic activity and stability of the final FeOOH@V-CoPNF composite catalyst.

[0057] S20, loading and reaction of V-Co precursor, preparation of V-Co precursor solution, including cobalt nitrate pentahydrate (Co(NO3)2·5H2O), ammonium metavanadate (NH4VO3), urea and ammonium fluoride (NH4F), and sufficient stirring and mixing, immersing the pretreated NF in the V-Co precursor solution, and transferring it to an autoclave, keeping the autoclave constant temperature at 120°C for 4h, and performing a hydrothermal reaction. After the reaction, take out the sample, wash it with ethanol and ultrapure water, and place it in a vacuum oven at 60°C for 10h to obtain a V-Co(OH)2 / NF intermediate;

[0058] The specific operation steps in step S20 include:

[0059] S201. Preparation of precursor solution: prepare the required chemicals, including Co(NO3)2.5H2O, NH4VO3, urea and NH4F, ensure that their purity and quality meet the experimental requirements, prepare an appropriate amount of deionized water or solvent as the basis of the solution, first add a certain amount of deionized water or solvent to a clean container, and then add Co(NO3)2.5H2O, NH4VO3, urea and NH4F to the container in sequence according to the proportion of the experimental design, and use a magnetic stirrer or a mechanical stirrer to stir and mix thoroughly until all solids are completely dissolved to form a uniform V-Co precursor solution;

[0060] S202. NF pretreatment: Use cleaning agents such as ethanol and ultrapure water to thoroughly clean the NF to remove oil, impurities and oxides on the surface. The cleaning process may need to be repeated several times to ensure the cleanliness of the NF surface. Place the cleaned NF in a dryer or use other drying methods to ensure that its surface is completely dry without residual moisture;

[0061] S203, loading and reaction: immerse the pretreated NF in the prepared V-Co precursor solution, ensure that the NF is completely immersed in the solution, and the solution can fully wet its surface. Soaking, spin coating or other appropriate methods can be used to ensure the uniform distribution of the precursor solution on the NF surface. Carefully transfer the NF loaded with the precursor solution to the autoclave, and pay attention to avoid damaging the NF or contaminating the precursor solution during the transfer process. Close the lid of the autoclave and ensure that it is well sealed. Set the temperature of the autoclave to 120°C, and turn on the heating system to keep the autoclave at this temperature for 4 hours, so that the V-Co precursor undergoes a hydrothermal reaction on the NF surface to form a V-Co(OH)2 / NF intermediate;

[0062] S204. Sample processing: After the reaction is completed, wait for the autoclave to cool down naturally to room temperature or cool down according to the safety operating procedures, open the lid of the autoclave, carefully take out the reacted NF, i.e., V-Co(OH)2 / NF intermediate, and clean the reacted sample with ethanol and ultrapure water to remove surface residues and unreacted precursors. The cleaning process may need to be repeated several times, and be careful not to damage the sample surface. Place the cleaned sample in a vacuum oven at 60°C and dry it for 10 hours to ensure that the sample will not be contaminated or damaged during the drying process.

[0063] The V-Co precursor solution (S201) is accurately prepared to ensure the accuracy of the proportion of each component in the solution, which is the basis for the formation of high-quality V-Co(OH)2 / NF intermediates. The solution is fully stirred using a magnetic or mechanical stirrer to ensure the uniformity of the solution and avoid the problem of uneven loading caused by uneven solution. Secondly, the NF pretreatment step (S202) completely removes the oil, impurities and oxides on the surface, providing a clean and highly active substrate for the loading of the precursor solution, which helps to improve the loading effect and the performance of the final product. The drying treatment ensures that there is no residual moisture on the NF surface, avoiding the negative impact of moisture in the subsequent reaction. Then, the loading and reaction step (S203) is carried out by immersion. The uniform distribution of the precursor solution on the NF surface is ensured by bubble, spin coating or other appropriate methods, which is the key to forming a uniform V-Co(OH)2 layer. The hydrothermal reaction conditions in the autoclave (120°C constant temperature for 4h) promote the hydrolysis and oxidation reaction of the V-Co precursor on the NF surface, and successfully generate a V-Co(OH)2 / NF intermediate with good structure and performance, providing a high-quality substrate for subsequent catalyst preparation. Finally, the sample processing step (S204) removes the residues and unreacted precursors on the surface of the sample after the reaction by cleaning and drying, ensuring the purity and dryness of the sample and avoiding performance degradation or contamination problems caused by residues during subsequent use or storage.

[0064] S30, preparation of V-CoP / NF, placing V-Co(OH)2 / NF intermediate and sodium hypophosphite monohydrate (NaH2PO2·H2O) in different positions of a tube furnace, respectively, heating the tube furnace to 300°C at a heating rate of 2°C / min under argon protection, and keeping the temperature for 1h for phosphating reaction, and taking out the sample after cooling naturally to room temperature to obtain V-CoP / NF;

[0065] Step S30 specifically includes the following steps:

[0066] S301, Preparation stage: Ensure that the V-Co(OH)2 / NF intermediate has been successfully prepared and cleaned according to the previous steps, prepare enough NaH2PO2·H2O as a phosphorus source, and confirm its purity and quality, check the integrity and cleanliness of the tube furnace and its accessories such as porcelain boats, thermocouples, etc., place the tube furnace on a stable laboratory table, and connect all necessary equipment and gas lines such as argon gas cylinders, gas flow meters, etc., to ensure that the heating system, temperature control system and gas protection system of the tube furnace are in normal working condition;

[0067] S302, sample placement: Place the V-Co(OH)2 / NF intermediate in the downstream position of the tube furnace, usually in a porcelain boat or similar container, and place NaH2PO2·H2O in the upstream position of the tube furnace to ensure that the phosphorus source can be smoothly decomposed and produce phosphating gas during the heating process;

[0068] S303, phosphating reaction: open the argon gas cylinder, adjust the gas flow meter, let the argon gas flow into the tube furnace at an appropriate flow rate, provide inert gas protection for the reaction, set the heating program of the tube furnace, start heating at a heating rate of 2°C / min, continue to pass argon during the heating process to ensure that the reaction is carried out in an inert atmosphere, monitor the temperature of the tube furnace, ensure that it is heated to 300°C according to the set program, when the temperature of the tube furnace reaches 300°C, maintain this temperature for phosphating reaction for 1 hour, continue to pass argon protection during the insulation period, and observe the reaction situation;

[0069] S304, Cooling and sampling: After the phosphating reaction is completed, turn off the heating system and let the tube furnace cool naturally to room temperature. Be careful not to rush to take out the sample to avoid damage due to a sudden drop in temperature. After the tube furnace is completely cooled, open the furnace door, take out the V-CoP / NF sample, check the appearance and integrity of the sample, and confirm whether the phosphating reaction is successful.

[0070] The meticulous arrangement of the preparation stage (S301) ensures the purity and quality of the experimental materials (such as NaH2PO2·H2O), which is the basis for ensuring the success of the subsequent phosphating reaction and the quality of the product. At the same time, the inspection of the integrity and cleanliness of the tube furnace and its accessories, as well as the debugging of the heating system, temperature control system and gas protection system, provide a stable and reliable environment for the experiment, avoiding experimental failure or product performance degradation due to equipment problems. Secondly, the reasonable layout of sample placement (S302) enables the phosphorus source (NaH2PO2·H2O) to decompose smoothly and produce phosphating gas. These gases flow to the V-Co(OH)2 / NF intermediate under the carrier of argon gas, realizing the effective progress of the phosphating reaction. This layout not only improves the phosphating efficiency, but also ensures sufficient contact between the reactants, which is beneficial to A uniform phosphating layer is formed. In the phosphating reaction (S303) stage, the flow rate of argon and the heating rate of the tube furnace are precisely controlled to ensure that the reaction is carried out in an inert atmosphere in a gentle and controllable manner. This control method avoids sample damage or product quality degradation due to excessively violent reactions, and also improves the repeatability and stability of the reaction. In addition, the temperature of the tube furnace is continuously monitored and ensured to be heated to the reaction temperature according to the set program, which further ensures the successful progress of the reaction. Finally, careful operation in the cooling and sampling (S304) stage avoids sample damage caused by a sudden drop in temperature, ensuring the accuracy and reliability of the experimental results. At the same time, the inspection of the appearance and integrity of the sample and the confirmation of whether the phosphating reaction is successful provide a strong guarantee for the subsequent catalyst performance testing and application.

[0071] In step S302, the positional relationship between the sample and the phosphorus source should ensure that the phosphating gas can fully contact the V-Co(OH)2 / NF intermediate, and contamination and damage should be avoided when placing the sample and the phosphorus source.

[0072] Ensuring that the phosphating gas can fully contact the V-Co(OH)2 / NF intermediate is the key to achieving an effective phosphating reaction. The phosphating gas generated by the decomposition of the phosphorus source during the heating process needs to be able to flow smoothly and evenly cover the surface of the V-Co(OH)2 / NF intermediate to ensure the uniformity and integrity of the phosphating reaction. The setting of this position relationship maximizes the contact opportunity between the phosphating gas and the sample surface through reasonable layout and airflow design, thereby improving the phosphating efficiency and product uniformity. Secondly, avoiding contamination and damage when placing samples and phosphorus sources is an important prerequisite for ensuring experimental success and product quality. The purity of samples and phosphorus sources has a direct impact on subsequent reactions and product performance. Any form of contamination may lead to reaction failure or product performance degradation. At the same time, the physical integrity of the sample is also a key factor for the success of the experiment. Any damage may lead to deviation or invalidity of the experimental results. Therefore, when placing samples and phosphorus sources, strict operating procedures and protective measures need to be taken, such as using clean tools, wearing gloves, and avoiding direct contact with the sample surface to ensure the purity and integrity of the sample and phosphorus source.

[0073] If there are residues or impurities on the sample surface, it can be cleaned with ethanol, ultrapure water, etc. The cleaned sample should be placed in a desiccator or dried in a vacuum oven. The dried V-CoP / NF sample should be properly stored in a dry, dust-free environment for subsequent use.

[0074] By cleaning the sample surface with solvents such as ethanol and ultrapure water, residues and impurities can be effectively removed. These solvents have good solubility and cleaning ability, and can penetrate into the tiny pores and cracks on the sample surface to completely remove the attached pollutants. This step is crucial to ensure the purity of the sample surface and the smooth progress of subsequent reactions, avoiding experimental errors or performance degradation caused by the presence of residues or impurities. Secondly, the cleaned samples need to be placed in a dryer or dried in a vacuum oven. The purpose of this step is to remove moisture and other volatile substances on the sample surface to prevent oxidation, corrosion or performance changes during subsequent storage or use. Drying ensures the stability and durability of the sample and provides reliable protection for subsequent experiments and applications. Finally, the dried V-CoP / NF samples are properly stored in a dry and dust-free environment to prevent the samples from being contaminated and damaged by the outside world. A dry environment can prevent the samples from absorbing moisture or being damp, and a dust-free environment can prevent impurities such as dust and particles from adhering to the sample surface. This storage method not only extends the shelf life of the sample, but also ensures that it can maintain its original performance and quality during use.

[0075] S40, electrodeposition and post-treatment of iron oxyhydroxide (FeOOH) layer, the V-CoP / NF sample was placed in 0.1M tetrahydrate and ferrous chloride (FeCl2.4H2O) solution as the working electrode, and a voltage of 0.8V was applied relative to the saturated calomel electrode for electrodeposition reaction for 10 minutes. After the electrodeposition, the sample was taken out and rinsed with ultrapure water several times to remove the residual solution and FeOOH nanoparticles that were not firmly attached. The sample was placed in a vacuum oven at 60°C and dried for 6 hours to obtain the final FeOOH@V-CoP / NF composite catalyst.

[0076] Step S40 specifically includes the following steps:

[0077] S401. Preparation before electrodeposition: prepare 0.1M FeCl2·4H2O solution as the electrolyte, ensure that the concentration of the solution is accurate and uniform, prepare other necessary electrodeposition equipment, such as electrodeposition tank, power supply, wire, etc., and check their working status, use V-CoP / NF sample as the working electrode, ensure that its surface is clean and free of contamination, and connect it correctly to the electrodeposition tank, select appropriate reference electrode such as saturated calomel electrode SCE and counter electrode, and connect them correctly to the electrodeposition tank;

[0078] S402, electrodeposition process: Use a power supply to apply a voltage of 0.8V to the working electrode V-CoP / NF relative to the saturated calomel electrode, keep the voltage stable, and ensure that the electrodeposition reaction can proceed smoothly. The electrodeposition reaction lasts for 10 minutes. During this period, the reaction situation should be closely monitored to ensure that the reaction proceeds as expected;

[0079] S403, post-electrodeposition treatment: After the electrodeposition is completed, the sample is immediately taken out and rinsed with ultrapure water for multiple times to remove the residual solution and FeOOH nanoparticles that are not firmly attached. The rinse should be done gently to avoid damaging the sample surface. The cleaned sample is placed in a vacuum oven at 60°C for drying for 6 hours to ensure that the sample is completely dry. The vacuum degree and temperature in the oven should be kept stable during the drying process;

[0080] S404. Final product and storage: After drying, take out the sample and check its appearance and performance to confirm that the FeOOH layer has been successfully deposited on the V-CoP / NF sample and there are no obvious defects on the sample surface. The final FeOOH@V-CoP / NF composite catalyst is properly stored in a dry and dust-free environment to avoid moisture or other contamination.

[0081] In the preparation stage before electrodeposition (S401), by accurately preparing 0.1M FeCl2·4H2O solution as the electrolyte, preparing and checking the electrodeposition equipment, it is ensured that the electrodeposition reaction can be carried out in a stable and controllable environment. The V-CoP / NF sample is selected as the working electrode, and its surface is ensured to be clean and pollution-free, which provides a good basis for the uniform deposition of FeOOH. At the same time, the appropriate reference electrode and counter electrode are selected, and they are correctly connected to the electrodeposition tank to ensure the accuracy and reliability of the electrodeposition reaction. Secondly, in the electrodeposition process (S402), by applying a stable voltage of 0.8V to the working electrode and continuing the electrodeposition reaction for 10 minutes, the effective deposition of FeOOH on the surface of the V-CoP / NF sample is achieved. In this process, the reaction situation is closely monitored to ensure that the reaction proceeds as expected, avoiding actual problems caused by improper operation or equipment failure. The test failed. Then, in the post-electrodeposition treatment stage (S403), the residual solution and the FeOOH nanoparticles that were not firmly attached were removed by immediately taking out the sample and rinsing it with ultrapure water for multiple times, thereby ensuring the purity of the sample and the firmness of the FeOOH layer. Subsequently, the cleaned sample was placed in a vacuum oven at 60°C for drying, thereby ensuring that the sample would not be contaminated or damaged during the drying process. At the same time, the vacuum degree and temperature in the oven were kept stable, further improving the drying effect. Finally, in the final product and storage stage (S404), by checking the appearance and performance of the sample, it was confirmed that the FeOOH layer had been successfully deposited on the V-CoP / NF sample, and there were no obvious defects on the sample surface. The final FeOOH@V-CoP / NF composite catalyst was properly stored in a dry and dust-free environment to avoid it from being affected by moisture or other contamination, thereby ensuring the long-term stability and availability of the catalyst.

[0082] Electrocatalytic process: The electrochemical measurements were performed on a CHI 660E electrochemical workstation using a typical three-electrode configuration. Graphite rod and platinum wire electrodes were used as counter electrodes for HER and OER, respectively, while Hg / HgO electrodes were used as reference electrodes. The prepared catalyst was used as a working electrode after being cut into a size of 1.0 cm × 1.0 cm on NF. Linear sweep voltammetry (LSV) tests were performed in 1.0 molar KOH aqueous solution with 95% iR compensation and a scan rate of 5 mV / s.

[0083] In the pretreatment stage (S10), NF, as the substrate material, was ultrasonically treated with a hydrochloric acid solution to remove surface oxides and impurities. Subsequently, further ultrasonic treatment in acetone, ethanol and deionized water and vacuum drying ensured the cleanliness of the NF substrate and suitable subsequent reaction conditions. Next, in the loading and reaction stage of the V-Co precursor (S20), a V-Co precursor solution containing specific components was prepared and a V-Co(OH)2 precursor layer was successfully loaded on the NF substrate by means of a hydrothermal reaction. This process not only achieved a uniform distribution of the V-Co element on the NF surface, but also promoted the formation and curing of the precursor layer through a hydrothermal reaction, which provided a foundation for the subsequent phosphating. The reaction laid the foundation. Subsequently, in the preparation stage of V-CoP / NF (S30), the V-Co(OH)2 / NF intermediate was converted into V-CoP / NF by the phosphating reaction in the tube furnace. The heating rate, reaction temperature and holding time of the tube furnace were precisely controlled to ensure the smooth progress of the phosphating reaction and the purity of the product. At the same time, argon protection avoided possible oxidation or contamination during the reaction and ensured the quality of the product. Finally, in the electrodeposition and post-treatment stage of the FeOOH layer (S40), the V-CoP / NF sample was placed in the FeCl2·4H2O electrolyte as the working electrode for the electrodeposition reaction. At a specific voltage, Fe 2+ The ions were oxidized to FeOOH on the surface of V-CoP / NF and deposited to form a uniform FeOOH layer. After the electrodeposition, the residual solution and the FeOOH nanoparticles that were not firmly attached were removed by ultrapure water rinsing and vacuum drying to obtain the final FeOOH@V-CoP / NF composite catalyst.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a FeOOH@V-CoP composite catalyst, characterized in that: The following steps are involved: S10, NF pretreatment, cutting the NF into 3.0 cm × 2.0 cm rectangular pieces, placing the NF in a 3.0 M hydrochloric acid solution, ultrasonically treating for 20 min, then ultrasonically treating in acetone, ethanol and deionized water for 10 min each, placing the cleaned NF in a vacuum oven at 60 ° C to dry for later use; S20, loading and reaction of V-Co precursor, preparing V-Co precursor solution, including Co(NO3)2·5H2O, NH4VO3, urea and NH4F, and fully stirring and mixing, immersing the pretreated NF in the V-Co precursor solution, and transferring it to an autoclave, keeping the autoclave constant temperature at 120°C for 4h, and performing a hydrothermal reaction. After the reaction, taking out the sample, washing it with ethanol and ultrapure water, and drying it in a vacuum oven at 60°C for 10h, to obtain a V-Co(OH)2 / NF intermediate; S30, preparation of V-CoP / NF, placing V-Co(OH)2 / NF intermediate and NaH2PO2·H2O in different positions of a tube furnace, respectively, heating the tube furnace to 300°C at a heating rate of 2°C / min under argon protection, and keeping the temperature for 1h for phosphating reaction, and taking out the sample after cooling naturally to room temperature to obtain V-CoP / NF; S40, electrodeposition and post-treatment of FeOOH layer, the V-CoP / NF sample was placed in a 0.1M FeCl2.4H2O solution as the working electrode, a voltage of 0.8V was applied relative to the saturated calomel electrode, and the electrodeposition reaction was carried out for 10 minutes. After the electrodeposition, the sample was taken out and rinsed with ultrapure water several times to remove the residual solution and the FeOOH nanoparticles that were not firmly attached. The sample was placed in a vacuum oven at 60°C and dried for 6 hours to obtain the final FeOOH@V-CoP / NF composite catalyst.

2. The method for preparing a FeOOH@V-CoP composite catalyst according to claim 1, characterized in that: The step S10 specifically includes the following steps: S101, cutting NF: Use appropriate cutting tools such as scissors, cutting machine or laser cutting machine to accurately cut NF into rectangular pieces with a size of 3.0 cm × 2.0 cm, ensuring that the cutting edges are flat and the size is accurate; S102, oxide layer removal treatment: prepare a container and add a sufficient amount of 3.0M hydrochloric acid solution to ensure that the solution is sufficient to completely immerse the NF, carefully place the cut NF into the hydrochloric acid solution, ensure that all surfaces are in contact with the solution, place the container containing the NF and the hydrochloric acid solution in an ultrasonic cleaning machine, turn on the ultrasonic treatment function, and the treatment time is 20 minutes; S103, deep cleaning: After cleaning, remove the NF from the hydrochloric acid solution and rinse it with deionized water to remove residual hydrochloric acid. Prepare three containers containing acetone, ethanol and deionized water respectively and arrange them in order. First, put the NF into acetone and perform ultrasonic treatment for 10 minutes. Acetone helps to remove organic pollutants. Then, take the NF out of acetone and put it into ethanol for 10 minutes of ultrasonic treatment. Ethanol is used for further cleaning and removal of residues. Finally, take the NF out of ethanol and put it into deionized water for 10 minutes of ultrasonic treatment. Deionized water is used to thoroughly rinse and remove all residual chemicals. S104, drying treatment: take out the cleaned NF from the deionized water, use a clean nitrogen gun or natural air drying to preliminarily remove the surface moisture, place the NF in a dry and clean container, and put the container into a vacuum oven at 60°C, turn on the oven, set the temperature to 60°C, and turn on the vacuum pump to create a vacuum environment to ensure complete removal of moisture; S105. Reserve: After drying, take the NF out of the oven and store it in a dry, dust-free environment for subsequent use. Be careful to avoid contact with pollutants to keep it clean.

3. The method for preparing a FeOOH@V-CoP composite catalyst according to claim 1, characterized in that: The specific operation steps in step S20 include: S201. Preparation of precursor solution: prepare the required chemicals, including Co(NO3)2.5H2O, NH4VO3, urea and NH4F, ensure that their purity and quality meet the experimental requirements, prepare an appropriate amount of deionized water or solvent as the basis of the solution, first add a certain amount of deionized water or solvent to a clean container, and then add Co(NO3)2.5H2O, NH4VO3, urea and NH4F to the container in sequence according to the proportion of the experimental design, and use a magnetic stirrer or a mechanical stirrer to stir and mix thoroughly until all solids are completely dissolved to form a uniform V-Co precursor solution; S202. NF pretreatment: Use cleaning agents such as ethanol and ultrapure water to thoroughly clean the NF to remove oil, impurities and oxides on the surface. The cleaning process may need to be repeated several times to ensure the cleanliness of the NF surface. Place the cleaned NF in a dryer or use other drying methods to ensure that its surface is completely dry without residual moisture; S203, loading and reaction: immerse the pretreated NF in the prepared V-Co precursor solution, ensure that the NF is completely immersed in the solution, and the solution can fully wet its surface. Soaking, spin coating or other appropriate methods can be used to ensure the uniform distribution of the precursor solution on the NF surface. Carefully transfer the NF loaded with the precursor solution to the autoclave, and pay attention to avoid damaging the NF or contaminating the precursor solution during the transfer process. Close the lid of the autoclave and ensure that it is well sealed. Set the temperature of the autoclave to 120°C, and turn on the heating system to keep the autoclave at this temperature for 4 hours, so that the V-Co precursor undergoes a hydrothermal reaction on the NF surface to form a V-Co(OH)2 / NF intermediate; S204. Sample processing: After the reaction is completed, wait for the autoclave to cool down naturally to room temperature or cool down according to the safety operating procedures, open the lid of the autoclave, carefully take out the reacted NF, i.e., V-Co(OH)2 / NF intermediate, and clean the reacted sample with ethanol and ultrapure water to remove surface residues and unreacted precursors. The cleaning process may need to be repeated several times, and be careful not to damage the sample surface. Place the cleaned sample in a vacuum oven at 60°C and dry it for 10 hours to ensure that the sample will not be contaminated or damaged during the drying process.

4. The method for preparing a FeOOH@V-CoP composite catalyst according to claim 1, characterized in that: The step S30 specifically includes the following steps: S301, Preparation stage: Ensure that the V-Co(OH)2 / NF intermediate has been successfully prepared and cleaned according to the previous steps, prepare enough NaH2PO2·H2O as a phosphorus source, and confirm its purity and quality, check the integrity and cleanliness of the tube furnace and its accessories such as porcelain boats, thermocouples, etc., place the tube furnace on a stable laboratory table, and connect all necessary equipment and gas lines such as argon gas cylinders, gas flow meters, etc., to ensure that the heating system, temperature control system and gas protection system of the tube furnace are in normal working condition; S302, sample placement: Place the V-Co(OH)2 / NF intermediate in the downstream position of the tube furnace, usually in a porcelain boat or similar container, and place NaH2PO2·H2O in the upstream position of the tube furnace to ensure that the phosphorus source can be smoothly decomposed and produce phosphating gas during the heating process; S303, phosphating reaction: open the argon gas cylinder, adjust the gas flow meter, let the argon gas flow into the tube furnace at an appropriate flow rate, provide inert gas protection for the reaction, set the heating program of the tube furnace, start heating at a heating rate of 2°C / min, continue to pass argon during the heating process to ensure that the reaction is carried out in an inert atmosphere, monitor the temperature of the tube furnace, ensure that it is heated to 300°C according to the set program, when the temperature of the tube furnace reaches 300°C, maintain this temperature for phosphating reaction for 1 hour, continue to pass argon protection during the insulation period, and observe the reaction situation; S304, Cooling and sampling: After the phosphating reaction is completed, turn off the heating system and let the tube furnace cool naturally to room temperature. Be careful not to rush to take out the sample to avoid damage due to a sudden drop in temperature. After the tube furnace is completely cooled, open the furnace door, take out the V-CoP / NF sample, check the appearance and integrity of the sample, and confirm whether the phosphating reaction is successful.

5. The method for preparing a FeOOH@V-CoP composite catalyst according to claim 4, characterized in that: The positional relationship between the sample and the phosphorus source in step S302 should ensure that the phosphating gas can fully contact the V-Co(OH)2 / NF intermediate, and contamination and damage should be avoided when placing the sample and the phosphorus source.

6. The method for preparing a FeOOH@V-CoP composite catalyst according to claim 4, characterized in that: If there are residues or impurities on the surface of the sample, it can be cleaned with ethanol, ultrapure water, etc. The cleaned sample should be placed in a desiccator or dried in a vacuum oven. The dried V-CoP / NF sample should be properly stored in a dry, dust-free environment for subsequent use.

7. The method for preparing a FeOOH@V-CoP composite catalyst according to claim 1, characterized in that: The step S40 specifically includes the following steps: S401. Preparation before electrodeposition: prepare 0.1M FeCl2·4H2O solution as the electrolyte, ensure that the concentration of the solution is accurate and uniform, prepare other necessary electrodeposition equipment, such as electrodeposition tank, power supply, wire, etc., and check their working status, use V-CoP / NF sample as the working electrode, ensure that its surface is clean and free of contamination, and connect it correctly to the electrodeposition tank, select appropriate reference electrode such as saturated calomel electrode SCE and counter electrode, and connect them correctly to the electrodeposition tank; S402, electrodeposition process: Use a power supply to apply a voltage of 0.8V to the working electrode V-CoP / NF relative to the saturated calomel electrode, keep the voltage stable, and ensure that the electrodeposition reaction can proceed smoothly. The electrodeposition reaction lasts for 10 minutes. During this period, the reaction situation should be closely monitored to ensure that the reaction proceeds as expected; S403, post-electrodeposition treatment: After the electrodeposition is completed, the sample is immediately taken out and rinsed with ultrapure water for multiple times to remove the residual solution and FeOOH nanoparticles that are not firmly attached. The rinse should be done gently to avoid damaging the sample surface. The cleaned sample is placed in a vacuum oven at 60°C for drying for 6 hours to ensure that the sample is completely dry. The vacuum degree and temperature in the oven should be kept stable during the drying process; S404. Final product and storage: After drying, take out the sample and check its appearance and performance to confirm that the FeOOH layer has been successfully deposited on the V-CoP / NF sample and there are no obvious defects on the sample surface. The final FeOOH@V-CoP / NF composite catalyst is properly stored in a dry and dust-free environment to avoid moisture or other contamination.

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