A nitrogen-doped carbon nanoflower loaded CoP / NiCoP heterostructure, a preparation method and application thereof

Abstract

The application discloses nitrogen-doped carbon nanoflower loaded CoP / NiCoP heterostructures and a preparation method and application thereof. The preparation method comprises the following steps: 1) uniformly mixing transition metal salts, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and 2-methyl imidazole, and then performing solvent thermal co-precipitation treatment to obtain Ni / ZIF-67 nanoflowers; 2) placing the obtained Ni / ZIF-67 nanoflowers and sodium hypophosphite in an inert atmosphere, and then performing programmed temperature rising to 300-400 DEG C, and then performing heat preservation for 10-60 min, so that the CoP / NiCoP@N-CNF carbon nanoflower heterostructure is obtained. Compared with the prior art, the method is simple in operation, low in cost and easy to scale production, and the prepared nanoflowers have the advantages of high specific surface area, many active sites, good conductivity and high catalytic activity.

Description

Technical Field

[0001] This invention relates to a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure, its preparation method and application, belonging to the field of water electrolysis catalyst technology. Background Technology

[0002] Driven by increasingly severe energy dilemmas and environmental problems, research into clean and sustainable energy sources to reduce dependence on traditional fossil fuels has gained widespread recognition. Hydrogen energy, with its environmental friendliness and recyclability, is a promising alternative to fossil fuels. Among various hydrogen production methods, water electrolysis is an efficient and green method, characterized by its simple operation and pure products, with the hydrogen evolution reaction (HER) being the key reaction.

[0003] Currently, Pt-based noble metal materials are the optimal HER catalysts. However, their high cost, scarcity, and poor stability significantly limit their large-scale application. Lu et al. summarized that a common method for noble metal nanocatalysts is colloidal synthesis, but this method usually requires post-treatment (such as annealing) to remove residual ligands and clean the surface of the nanocatalyst. These post-treatments alter the surface structure of the nanoparticles, deactivating their catalytic performance. Therefore, in the long term, developing other low-cost, high-strength, and highly active HER electrocatalysts is crucial.

[0004] To address this issue, transition metals are considered promising alternatives to noble metals, including transition metal phosphides, carbides, and nitrides. Currently, various morphologies of transition metal (Co, Ni, Fe) phosphides have been prepared, such as nanorods, nanowires, and nanoflowers. Among the reported structures, flower-like hierarchical structures possess a larger specific surface area, exposing more active sites, and also offer advantages such as abundant electrolyte permeation channels and good self-supporting stability. Furthermore, bimetallic TMPs (such as NiCoP and FeCoP) exhibit excellent HER performance due to their strong hydrogen bonding. For example, introducing other cations into cobalt phosphide-based catalysts facilitates charge redistribution, induces changes in electronic structure, optimizes hydrogen adsorption free energy, and improves intrinsic activity. However, limitations remain, such as the difficulty in controlling the number and dispersion of dopants; therefore, reports on their use in HER are still quite limited. Summary of the Invention

[0005] To address the challenges of controlling the number and dispersion of dopants, this invention aims to provide a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure, its preparation method, and the application of the catalyst obtained by this method in water electrolysis for hydrogen production. This invention obtains flower-like Ni / ZIF-67 through solvothermal co-precipitation, followed by low-temperature phosphating to transform it into a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure. This results in a catalyst with more catalytic active sites and a larger active surface area, thereby improving its stability.

[0006] To address the problems of the existing technology, the present invention adopts the following technical solution:

[0007] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0008] 1) Preparation of Ni / ZIF-67 nanoflower precursor: Cobalt salt and nickel salt were added to methanol as solvent to form solution A. 2-methylimidazole was added to methanol as solvent to form solution B. After dissolution, solution A was added dropwise to solution B. After ultrasonic mixing, a hydrothermal reaction was carried out. After the reaction was completed, the Ni / ZIF-67 nanoflower precursor was obtained by centrifugation and drying.

[0009] 2) The obtained Ni / ZIF-67 nanoflower precursor and sodium hypophosphite were heated to 300-400℃ in an inert atmosphere, held for 10-60 min, and then cooled to obtain a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure.

[0010] As an improvement, the cobalt salt is cobalt nitrate hexahydrate and the nickel salt is nickel nitrate hexahydrate.

[0011] As an improvement, the temperature of the hydrothermal reaction in step 1) is 120°C and the hydrothermal reaction time is 3-5 hours.

[0012] As an improvement, the mass ratio of Ni / ZIF-67 nanoflower precursor to sodium hypophosphite in step 2) is 1:20.

[0013] As an improvement, the heating rate of the programmed temperature rise in step 2) is 2°C / min.

[0014] The nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure prepared by the above method is a three-dimensional nanoflower with a regular shape. A large number of CoP / NiCoP nanoparticles with high uniformity and good dispersion are distributed on the carbon nanoflowers with a particle size of about 10 nm. The nanoflowers have abundant pores, which are beneficial to electron transfer.

[0015] The above-mentioned nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure is used as a catalyst in water electrolysis.

[0016] Principle: Using transition metal (Co, Ni) nitrates as the metal source and 2-methylimidazole as the ligand, Ni / ZIF-67 is generated. This is then used to prepare a CoP / NiCoP heterostructure supported on carbon nanoflowers through low-temperature phosphating. The catalyst is a three-dimensional nanoflower with a regular shape and a large number of highly uniform and well-dispersed nanoparticles distributed on the carbon nanosheets. During the low-temperature phosphating process, 2-methylimidazole acts as both the carbon and nitrogen source, transforming it into nitrogen-doped carbon nanoflowers, while the introduction of Ni... 2+ This facilitates charge redistribution, induces changes in electronic structure, optimizes hydrogen adsorption free energy, and enhances intrinsic activity, ensuring that the obtained nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure has high electrocatalytic activity and stability as a catalyst.

[0017] The nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure prepared in this invention has the following advantages:

[0018] 1) The flower-like hierarchical structure has a large specific surface area, which can expose more active sites and accelerate electron transfer and electrolyte penetration;

[0019] 2) Ni 2+ The synergistic effect between heterostructures brought about by the introduction of [the catalyst] is beneficial to changing the electronic structure of the catalyst, promoting electron transport, and thus improving the catalytic performance of the catalyst.

[0020] 3) The catalyst has a heterogeneous structure composed of phosphides, which is stable in composition; the three-dimensional flower-like structure is stable and durable, thus exhibiting good electrochemical stability.

[0021] Beneficial effects:

[0022] Compared with existing technologies, the present invention provides a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure, its preparation method, and its application, which have the following advantages:

[0023] 1) This invention prepares nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructures using a simple and scalable low-temperature Ni / ZIF-67 precursor phosphating method.

[0024] 2) The reactants selected in this invention are inexpensive, the method is simple and easy to implement, the operating cost is low, the equipment is simple, and large-scale production can be achieved.

[0025] 3) The product obtained by this invention has a multi-level structure with a regular shape, and is a heterogeneous structure, exhibiting high electrocatalytic activity (overpotential of 106 mV and Tafel slope of 79.7 mV dec).-1 With its high stability (12h) and other characteristics, it is a highly promising catalyst for water electrolysis, with broad application prospects in the future energy industry. Attached Figure Description

[0026] Figure 1 This is a low-magnification TEM image of CoP / NiCoP@N-CNF prepared by the method in Example 1;

[0027] Figure 2 This is the SEM image of CoP / NiCoP@N-CNF prepared by the method in Example 1;

[0028] Figure 3 This is a magnified SEM image of CoP / NiCoP@N-CNF prepared by the method in Example 1;

[0029] Figure 4 This is a high-magnification TEM image of CoP / NiCoP@N-CNF prepared by the method in Example 1;

[0030] Figure 5 The XRD pattern of CoP / NiCoP@N-CNF prepared by the method in Example 1;

[0031] Figure 6 The CoP / NiCoP@N-CNF prepared by the method in Example 1 and the CoP / NiCoP@N-CNF without Ni introduction are compared. 2+ Spectrum of alkaline hydrogen evolution performance of CoP / Co2P@N-CNF;

[0032] Figure 7 This is the alkaline hydrogen evolution stability test spectrum of CoP / NiCoP@N-CNF prepared by the method in Example 1. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0034] Example 1

[0035] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0036] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 1:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0037] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0038] Example 2

[0039] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0040] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g Co(NO3)2·6H2O and 2.184 g Ni(NO3)2·6H2O (Co:Ni = 1:2) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0041] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0042] Example 3

[0043] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0044] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g Co(NO3)2·6H2O and 3.276 g Ni(NO3)2·6H2O (Co:Ni = 1:3) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0045] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0046] Example 4

[0047] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0048] 1) Preparation of Ni / ZIF-67 precursor: 2.184 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 2:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0049] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0050] Example 5

[0051] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0052] 1) Preparation of Ni / ZIF-67 precursor: 3.276 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 3:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0053] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0054] Example 6

[0055] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0056] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 1:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 3 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0057] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0058] Example 7

[0059] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0060] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 1:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 5 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0061] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a programmed temperature increase of 2°C / min under an inert atmosphere and held at this temperature for 30 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0062] Example 8

[0063] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0064] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 1:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0065] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a program temperature of 2°C / min under an inert atmosphere and held at this temperature for 10 min. Then it was cooled to obtain the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure.

[0066] Example 9

[0067] A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure includes the following steps:

[0068] 1) Preparation of Ni / ZIF-67 precursor: 1.092 g of Co(NO3)2·6H2O and 1.092 g of Ni(NO3)2·6H2O (Co:Ni = 1:1) were weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120 °C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60 °C to obtain the Ni / ZIF-67 nanoflower precursor.

[0069] 2) Preparation of CoP / NiCoP@N-CNF: Ni / ZIF-67 and sodium hypophosphite were mixed at a mass ratio of 1:20. Sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. The boat was heat-treated at 350°C with a program temperature of 2°C / min under an inert atmosphere and held at this temperature for 60 min. After cooling, the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure was obtained.

[0070] Comparative Example 1

[0071] CoP / Co2P@N-CNF was prepared using the same method as in the first step of Example 1, except that nickel ions were not added in step 1) of this example. Specifically, 1.092 g of Co(NO3)2·6H2O was weighed and dissolved in 15 mL of methanol to form solution A. Then, 0.616 g of 2-methylimidazole was dissolved in 15 mL of methanol to form solution B. After dissolution, solution A was added dropwise to solution B and sonicated for 10 minutes. Subsequently, the mixed solution was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 120°C for 4 hours. After cooling to room temperature, the obtained sample was washed several times with methanol and dried overnight at 60°C to obtain ZIF-67.

[0072] 2) Preparation of CoP / Co2P@N-CNF: According to the mass ratio of ZIF-67 and sodium hypophosphite of 1:20, sodium hypophosphite and the powder obtained in step 1) were placed at the front and end of a ceramic boat, respectively. Under an inert atmosphere, the temperature was increased to 350℃ at a programmed rate of 2℃ / min for heat treatment, and held at this temperature for 30min. Then, the temperature was cooled to obtain the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure.

[0073] The nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructures prepared in Example 1 were physically characterized using TEM, HRTEM, SEM, and XRD. All electrochemical tests were performed using a Shanghai Chenhua 660C electrochemical workstation in a three-electrode system. The three-electrode system used a glassy carbon electrode (GCE, d = 3 mm, S = 0.0706 cm). 2 A saturated calomel electrode (SCE) and a saturated calomel electrode (SCE) were used as the working electrode and reference electrode, respectively, while a carbon rod served as an auxiliary electrode during testing. From low-magnification TEM (… Figure 1 ) and SEM ( Figure 2 and Figure 3 As can be seen from the HRTEM images, the catalyst prepared according to the method described in Example 1 has a rough, porous, three-dimensional flower-like hierarchical structure, which can provide more active sites, shorten the diffusion path of substances, and facilitate faster electron transfer and electrolyte penetration. Further magnified HRTEM images show... Figure 4The spectrum shows that the lattice fringe spacing of CoP is 0.20 nm, which is an orthorhombic CoP, while the lattice fringe spacing of NiCoP is 0.22 nm, which corresponds to the orthorhombic NiCoP. A clear heterostructure interface can also be seen. Figure 5 The XRD pattern of CoP / NiCoP@N-CNF is shown. By comparing it with the standard pattern, its diffraction peaks are completely consistent with the standard cards of orthorhombic CoP (JCPDS No. 65-2593) and NiCoP (JCPDS No. 71-2336), indicating that a CoP / NiCoP heterostructure has been formed.

[0074] Examples 2-9 were tested using the same method. The test results show that, in Examples 1-5 of the present invention, by changing the ratio of Co to Ni, it was proven that the metal content has no significant effect on the structure and performance.

[0075] The heterostructures obtained by changing the phosphating time in Examples 1 and 8-9 have a similar flower-like structure to the heterostructures obtained by changing the hydrothermal reaction time in Examples 1 and 6-7.

[0076] The basic hydrogen evolution performance of the heterostructures of Example 1 and Comparative Example 1 was tested, and the specific steps are as follows:

[0077] 5 mg of catalyst was ultrasonically dispersed in 1 mL of an ethanol-water mixture (water:ethanol volume ratio 3:1) to prepare catalyst ink. Subsequently, 12 μL of the solution was dropped onto the surface of a glassy carbon electrode and dried in an oven at 40 °C. Then, 2 μL of Nafion solution was dropped onto the catalyst-coated glassy carbon electrode. Before HER testing, N2 was bubbled through a 1 M KOH electrolyte for at least 20 min to fill the electrolyte. The linear sweep voltammetry (LSV) assay used for HER testing was then performed in this electrolyte at a scan rate of 5 mV / s. -1 .

[0078] The results are as follows Figure 6 As shown, the heterostructure of Example 1, as a catalyst, achieves a current of 10 mA cm⁻¹. -2 It requires only 106mV overpotential, which is significantly higher than CoP / Co2P@N-CNF without nickel (139mV).

[0079] The hydrogen evolution stability of the heterostructure in Example 1 was tested, and the specific steps are as follows:

[0080] All electrochemical tests were performed using a Shanghai Chenhua 660C electrochemical workstation in a three-electrode system. The three-electrode system used a glassy carbon electrode (GCE, d = 3 mm, S = 0.0706 cm). 2The saturated calomel electrode (SCE) and the reference electrode are used as the working electrode and the reference electrode, respectively, while the carbon rod is used as the auxiliary electrode during the test.

[0081] The structure is obtained as follows Figure 7 As shown, the results indicate that the catalyst performance did not decline after 12 hours of chronoamperometry testing. This material has broad application prospects as a water electrolysis catalyst.

[0082] In summary, this invention uses transition metal (Co, Ni) nitrates as the metal source and 2-methylimidazole as the ligand to generate Ni / ZIF-67. This Ni / ZIF-67 is then used for low-temperature phosphating to prepare carbon nanoflower-supported CoP / NiCoP heterostructures. The nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure exhibits a large specific surface area, exposing more active sites and accelerating electron transfer and electrolyte penetration, while also demonstrating stable composition. The three-dimensional flower structure provides stability and durability, resulting in good electrochemical stability.

Claims

1. A method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure, characterized in that, Includes the following steps: 1) Preparation of Ni / ZIF-67 nanoflower precursor: Cobalt salt and nickel salt were added to methanol as solvent to form solution A. 2-methylimidazole was added to methanol as solvent to form solution B. After dissolution, solution A was added dropwise to solution B. After ultrasonic mixing, a hydrothermal reaction was carried out. After the reaction was completed, the solution was centrifuged and dried to obtain Ni / ZIF-67 nanoflower precursor. The cobalt salt was cobalt nitrate hexahydrate, and the nickel salt was nickel nitrate hexahydrate. The mass ratio of cobalt salt to nickel salt was 1:1, 1:2, 1:3, 2:1, or 3:

1. 2) The obtained Ni / ZIF-67 nanoflower precursor and sodium hypophosphite were heated to 300~400℃ in an inert atmosphere and held for 10~60 min to obtain the nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure.

2. The method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure according to claim 1, characterized in that, The hydrothermal reaction temperature in step 1) is 120℃, and the hydrothermal reaction time is 3-5h.

3. The method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure according to claim 1, characterized in that, In step 2), the mass ratio of Ni / ZIF-67 nanoflower precursor to sodium hypophosphite is 1:

20.

4. The method for preparing a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure according to claim 1, characterized in that, The heating rate of the programmed temperature rise in step 2) is 2~10℃ / min.

5. A nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure prepared by any one of the preparation methods of claims 1-4, characterized in that, The nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure is a three-dimensional nanoflower with a regular shape. A large number of highly uniform and well-dispersed CoP / NiCoP nanoparticles are distributed on the carbon nanoflowers, with a particle size of about 10 nm. The carbon nanoflowers also have abundant pores, which are beneficial for electron transfer.

6. The application of a nitrogen-doped carbon nanoflower-supported CoP / NiCoP heterostructure prepared by the preparation method described in claim 1 as a catalyst in water electrolysis.

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