Alkaline electrolytic water hydrogen evolution catalyst of Pt-Co core-shell nanocluster loaded VN / CNT composite carrier

Abstract

The invention relates to the technical field of catalysts, in particular to an alkaline electrolytic water hydrogen evolution catalyst of a Pt-Co core-shell nanocluster loaded VN / CNT composite carrier, which comprises a composite carrier and a core-shell nanocluster loaded on the composite carrier, the composite carrier is a VN / CNT composite carrier, and the core-shell nano-cluster is a Pt-Co core-shell nano-cluster; the Pt-Co core-shell nano-cluster takes Pt as a core and Co as a shell, and the particle size of the core-shell is 1-15 nm; the VN / CNT composite carrier comprises CNT and VN nanoparticles loaded on the CNT, and the mass fraction of VN is 5%-40%. In the Pt-Co core-shell structure, the Co shell layer optimizes the d band center of Pt through an electronic effect, and reduces the adsorption energy barrier of H *; meanwhile, the Co shell serves as a co-catalyst, dissociation of H2O under the alkaline condition is remarkably promoted, and compared with a single Pt catalyst, the activity is improved by 30% or above under the same Pt dosage.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to an alkaline water electrolysis hydrogen evolution catalyst with a Pt-Co core-shell nanocluster loaded VN / CNT composite carrier. Background Art

[0002] As the global energy crisis and environmental issues become increasingly prominent, hydrogen, as a clean and efficient secondary energy source, is considered an ideal alternative to traditional fossil fuels. Alkaline water electrolysis hydrogen evolution technology, with its advantages such as low equipment cost and safe operation, has become an important method for large-scale hydrogen production. However, efficient and stable hydrogen evolution catalysts are the core bottleneck for the industrialization of this technology.

[0003] Currently, commercial hydrogen evolution catalysts are primarily based on the precious metal Pt, but these materials are scarce, expensive, and exhibit slow reaction kinetics and poor stability in alkaline environments. To address these issues, researchers have attempted to improve catalytic performance through methods such as support optimization and metal nanostructure manipulation. Regarding supports, carbon nanotubes (CNTs) are widely used due to their excellent conductivity and large surface area. However, the lack of active sites on the surface of individual CNTs limits their ability to regulate the adsorption-desorption equilibrium of H*, resulting in limited catalytic activity. Vanadium nitride (VN) exhibits excellent hydrogen affinity and chemical stability, but its small surface area and insufficient conductivity make it prone to metal nanoparticle aggregation when used alone, resulting in low active site exposure. Regarding metal structure, Pt-Co alloys can reduce Pt usage, but the random arrangement of metal atoms prevents targeted regulation of active sites. In inverted core-shell structures, the Pt layer is directly exposed, susceptible to corrosion, and has low utilization. Single Pt nanoparticles, however, exhibit limited activity enhancement in alkaline conditions due to their weak ability to dissociate H2O.

[0004] Therefore, developing an alkaline water electrolysis hydrogen evolution catalyst with high activity, high stability and low noble metal usage has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose an alkaline water electrolysis hydrogen evolution catalyst with a Pt-Co core-shell nanocluster supported VN / CNT composite carrier.

[0006] A catalyst for hydrogen evolution during alkaline water electrolysis is characterized by comprising a composite support and core-shell nanoclusters supported on the composite support; the composite support is a VN / CNT composite support, and the core-shell nanoclusters are Pt-Co core-shell nanoclusters; the Pt-Co core-shell nanoclusters have Pt as a core and Co as a shell, and the particle size of the core and shell is 1-15 nm; the VN / CNT composite support comprises CNTs and VN nanoparticles supported on the CNTs, and the mass fraction of VN is 5%-40%.

[0007] Preferably, in the Pt-Co core-shell nanoclusters, the molar ratio of Pt to Co is 1:(1-3), and the shell thickness is 0.3-3 nm.

[0008] Preferably, the particle size of the VN nanoparticles is 3-30 nm; the length of the CNTs is 3-100 μm, and the diameter is 5-100 nm.

[0009] Preferably, the CNTs are pretreated with an acid solution, wherein the acid solution is a nitric acid solution or a mixed solution of sulfuric acid and nitric acid, and the concentration of the acid solution is 2-5 mol / L; in the mixed solution of sulfuric acid and nitric acid, the volume ratio of sulfuric acid to nitric acid is 1:(0.5-2).

[0010] A method for preparing the catalyst comprises the following steps:

[0011] (1) Preparation of VN / CNT composite carrier:

[0012] (101) treating the CNTs with acid, wherein the ultrasonic power of the acid treatment is 200-500 W and the treatment time is 1-3 hours;

[0013] (102) The acid-treated CNTs are dispersed in a solvent, a vanadium source, a nitrogen source, and an optional auxiliary agent are added, and the mixture is subjected to a hydrothermal reaction at a temperature of 170–200 °C for 8–15 h;

[0014] (103) The hydrothermal reaction product was dried and calcined at a temperature of 700–900 °C for 1–3 h to obtain a VN / CNT composite support;

[0015] (2) Preparation of Pt-Co core-shell nanoclusters:

[0016] (201) The platinum source is dissolved in a solvent, a protective agent is added, and after mixing, a first reducing agent is added. The reaction temperature is 70–90 °C to obtain Pt nanoparticles;

[0017] (202) A cobalt source was added to the Pt nanoparticles, and after mixing, a second reducing agent was added at a reaction temperature of 50–70 °C to obtain Pt-Co core-shell nanoclusters;

[0018] (3) The Pt-Co core-shell nanoclusters are loaded on a VN / CNT composite support to obtain the catalyst.

[0019] Preferably, in step (102), the vanadium source includes NH4VO3, the nitrogen source includes urea, and the auxiliary agent includes at least one of citric acid, EDTA or sodium citrate; in step (1) ③, the calcination atmosphere is a nitrogen atmosphere or a nitrogen-hydrogen mixed atmosphere, and the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed atmosphere is (8-10):1.

[0020] Preferably, in step (201), the platinum source includes H2PtCl6·6H2O, the protective agent includes PVP or PEG, and the first reducing agent includes NaBH4 or KBH4; in (202), the cobalt source includes Co(NO3)2·6H2O, and the second reducing agent includes ascorbic acid or hydrazine hydrate.

[0021] Preferably, in step (3), the stirring reaction temperature during the loading process is 20-40° C., and the reaction time is 2-5 hours; after loading, drying is performed at a drying temperature of 50-80° C. and a drying time of 8-15 hours.

[0022] An application of the catalyst in a hydrogen evolution reaction by alkaline water electrolysis, wherein the reaction system is an alkaline aqueous solution, the concentration of the alkali in the alkaline aqueous solution is 0.05-2 mol / L, and the alkali comprises at least one of KOH, NaOH or LiOH.

[0023] Preferably, the voltage range of the reaction is 0.01-0.5 V (vs RHE).

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. In the Pt-Co core-shell structure, the Co shell optimizes the Pt d-band center through electronic effects, reducing the adsorption energy barrier of H*. At the same time, the Co shell acts as a "co-catalyst", significantly promoting the dissociation of H2O under alkaline conditions. Compared with a single Pt catalyst, the activity is increased by more than 30% at the same Pt ​​dosage.

[0026] 2. In the VN / CNT composite carrier, the hydrogen affinity of VN regulates the adsorption-desorption equilibrium of H*, and the high conductivity of CNT accelerates electron transfer. The two work together to solve the problem of insufficient activity of a single carrier. Compared with Pt@Co / CNT and Pt@Co / VN, the overpotential is reduced by 20-30mV at high current density.

[0027] 3. In the Pt-Co core-shell structure, the Co shell provides physical protection for the Pt core, preventing Pt from being directly exposed to oxidation in an alkaline environment. Compared with the reverse core-shell structure, the activity retention rate is increased from 60% to more than 90% after 1,000 cycles.

[0028] 4. CNT provides a three-dimensional support skeleton for VN, inhibiting the agglomeration of VN nanoparticles; at the same time, the flexible structure of CNT alleviates the volume expansion stress during the reaction process, enhances the corrosion resistance of the carrier, and solves the problem of poor stability of a single VN carrier.

[0029] 5. In the Pt-Co core-shell structure, Pt as the core regulates activity only through electronic effects, without the need for large-scale exposure. Compared with Pt-Co alloys and single Pt catalysts, the Pt dosage is reduced by 40%-50%. At the same time, the high dispersion of the VN / CNT composite carrier enables the Pt-Co core-shell nanoclusters to be uniformly loaded, and the exposure rate of active sites is increased by more than 50%, further reducing the cost of precious metals per unit activity.

[0030] 6. The present invention achieves precise control of the catalyst structure and good product reproducibility through processes such as acid pretreatment to regulate CNT surface functional groups, step-by-step reduction to prepare core-shell structure, and atmosphere calcination to control VN crystallinity. In addition, the raw materials used are low-cost and easy to obtain, and the preparation process does not require harsh conditions, making it suitable for large-scale production. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] Example 1

[0033] Preparation of VN / CNT composite support

[0034] (1) Weigh 5 g of CNTs and add them to 200 mL of 3 mol / L nitric acid solution. Ultrasonicate at 300 W for 2 h, then filter, wash with deionized water until neutral, and dry at 80 °C for 12 h.

[0035] (2) The treated CNTs were dispersed in 100 mL of deionized water, 2 g of NH4VO3 and 5 g of urea were added, and the mixture was stirred for 30 minutes to uniformly mix. The mixture was then transferred to a 200 mL autoclave and reacted at 180 °C for 12 hours.

[0036] (3) After the reaction is completed, the product is cooled to room temperature, filtered, washed with deionized water and ethanol three times respectively, and dried at 80°C for 12 hours to obtain a precursor.

[0037] (4) The precursor was placed in a tubular furnace, heated to 800 °C at a rate of 5 °C / min under a nitrogen atmosphere, and calcined at this temperature for 2 h with the nitrogen flow rate controlled at 50 mL / min to obtain a VN / CNT composite support.

[0038] Notes: Control the power and time during ultrasonic treatment to ensure that the CNTs are fully dispersed; the sealing performance of the high-pressure reaction kettle should be good to avoid leakage during the reaction; accurately control the temperature, heating rate and nitrogen flow rate during calcination to avoid the generation of impurities.

[0039] Preparation of Pt-Co core-shell nanoclusters

[0040] (1) Dissolve 0.5 mmol of H2PtCl6·6H2O in 50 mL of deionized water, and after stirring uniformly, add 0.1 g of polyvinylpyrrolidone (PVP) as a protective agent, and continue stirring for 10 minutes. Then heat the solution to 80°C, and dropwise add 10 mL of a 0.1 mol / L NaBH4 solution, and after the dropwise addition is complete, incubate at 80°C for 1 hour to obtain a Pt nanoparticle solution.

[0041] (2) Cool the above Pt nanoparticle solution to room temperature, add 1 mmol of Co(NO3)2·6H2O, and after stirring uniformly, heat the solution to 60°C, and dropwise add 10 mL of a 0.1 mol / L ascorbic acid solution as a reducing agent, and after the dropwise addition is complete, incubate at 60°C for 2 hours to obtain a Pt@Co core-shell nanocluster solution.

[0042] Notes: Ensure complete dissolution when dissolving H2PtCl6·6H2O and Co(NO3)2·6H2O; slowly dropwise add the reducing agent to avoid excessively vigorous reaction; control the temperature during the reaction to ensure smooth reaction.

[0043] The structure of the Pt-Co core-shell nanoclusters is as follows Formula 1:

[0044]

[0045] Loading of Pt-Co core-shell nanoclusters onto a VN / CNT composite carrier

[0046] (1) Weigh 1 g of the prepared VN / CNT composite carrier, disperse it in 50 mL of deionized water, and ultrasonically treat for 30 minutes to fully disperse it. Slowly add the above Pt@Co core-shell nanocluster solution to the VN / CNT composite carrier dispersion, and stir at room temperature for 4 hours. After the reaction is complete, filter, wash with deionized water and ethanol three times each, and vacuum dry at 60°C for 12 hours to obtain a Pt@Co / VN-CNT catalyst.

[0047] Notes: The VN / CNT composite carrier should be fully dispersed to ensure uniform loading; control the stirring speed during the stirring reaction to avoid settling of the carrier; control the temperature and time during vacuum drying to ensure that the water is fully evaporated.

[0048] Example 2

[0049] Preparation of VN / CNT composite carrier

[0050] (1) 5 g of CNT was weighed and added to 200 mL of 4 mol / L nitric acid solution, and ultrasonic treatment was performed at a power of 400 W for 1.5 hours, followed by filtration, washing with deionized water until neutral, and drying at 90°C for 10 hours.

[0051] (2) The treated CNT was dispersed in 100 mL of deionized water, 2.5 g of NH4VO3, 5 g of urea and 0.5 g of citric acid (adjuvant) were added, and stirred for 30 minutes to uniformly mix, and then transferred to a 200 mL high-pressure reaction kettle, and reacted at 190°C for 10 hours.

[0052] (3) After the reaction was completed, it was cooled to room temperature, filtered, washed with deionized water and ethanol for 3 times respectively, and dried at 90°C for 10 hours to obtain a precursor. The precursor was placed in a tube furnace, heated to 850°C at a heating rate of 6°C / min under nitrogen atmosphere, and calcined at this temperature for 1.5 hours, with a nitrogen flow rate of 60 mL / min, to obtain a VN / CNT composite carrier.

[0053] Notes: Stir uniformly when adding citric acid adjuvant; after increasing the ultrasonic power, observe the dispersion of CNT to avoid damage to the structure of CNT caused by excessive ultrasonic; after adjusting the high-pressure reaction temperature and time appropriately, ensure that the reaction proceeds fully.

[0054] Preparation of Pt-Co core-shell nanoclusters

[0055] (1) 0.6 mmol of H2PtCl6·6H2O was dissolved in 50 mL of deionized water, and after stirring uniformly, 0.12 g of PVP was added, and stirring was continued for 10 minutes. Then the solution was heated to 85°C, and 12 mL of 0.1 mol / L NaBH4 solution was added dropwise, and after the addition was completed, the solution was incubated at 85°C for 1.5 hours to obtain a Pt nanoparticle solution.

[0056] (2) The above Pt nanoparticle solution was cooled to room temperature, 1.2 mmol of Co(NO3)2·6H2O was added, and after stirring uniformly, the solution was heated to 65°C, and 12 mL of 0.1 mol / L ascorbic acid solution was added dropwise, and after the addition was completed, the solution was incubated at 65°C for 1.5 hours to obtain a Pt@Co core-shell nanocluster solution.

[0057] Notes: After adjusting the amount of reactants, ensure that the proportions of the substances are appropriate; after appropriately increasing the reaction temperature, strengthen the monitoring of the temperature to prevent the agglomeration of nanoparticles caused by excessive temperature.

[0058] The mechanism of VN is shown in Equation 2 below:

[0059]

[0060] Loading Pt-Co core-shell nanoclusters onto VN / CNT composite supports

[0061] (1) Weigh 1 g of the prepared VN / CNT composite support and disperse it in 50 mL of deionized water. Ultrasonicate for 40 minutes to fully disperse it. Slowly add the above Pt@Co core-shell nanocluster solution to the VN / CNT composite support dispersion and stir at 30°C for 3 hours. After the reaction, filter, wash with deionized water and ethanol three times respectively, and vacuum dry at 70°C for 10 hours to obtain the Pt@Co / VN-CNT catalyst.

[0062] Note: When appropriately increasing the reaction temperature, pay attention to controlling the temperature stability; when the ultrasonic treatment time is extended, avoid excessive dispersion of the carrier, which may lead to difficulties in subsequent separation.

[0063] Example 3

[0064] Preparation of VN / CNT composite support

[0065] (1) Weigh 5 g of CNT and add it to 200 mL of a 2.5 mol / L mixed solution of sulfuric acid and nitric acid (volume ratio 1:1). Ultrasonicate at 350 W for 1.8 h, filter, wash with deionized water until neutral, and dry at 85 °C for 11 h.

[0066] (2) The treated CNTs were dispersed in 100 mL of deionized water, and 2.2 g of NH4VO3, 5 g of urea, and 0.3 g of ethylenediaminetetraacetic acid (EDTA, a dispersing aid) were added. The mixture was stirred for 40 minutes to uniformly mix, and then transferred to a 200 mL high-pressure reactor and reacted at 185 ° C for 11 hours. After cooling to room temperature, the mixture was filtered, washed with deionized water and ethanol three times respectively, and dried at 85 ° C for 11 hours to obtain a precursor. The precursor was placed in a tube furnace and heated to 820 ° C at a rate of 5.5 ° C / min in a nitrogen-hydrogen mixed atmosphere (volume ratio 9:1). It was calcined for 1.8 hours with a total gas flow rate of 55 mL / min to obtain a VN / CNT composite carrier.

[0067] Note: Mixed acid treatment must be performed in a fume hood to avoid leakage of acid mist; after adding EDTA, the stirring time must be extended to ensure sufficient complexation; during mixed atmosphere calcination, the gas ratio must be precisely controlled to prevent excessive reduction of CNTs.

[0068] Preparation of Pt-Co core-shell nanoclusters

[0069] (1) Dissolve 0.55 mmol of H2PtCl6·6H2O in 50 mL of deionized water and stir until uniform. Add 0.11 g of polyethylene glycol (PEG, molecular weight 2000) as a protective agent and continue stirring for 15 minutes. Heat the solution to 82°C and add 11 mL of 0.1 mol / L KBH4 solution dropwise. After the addition is complete, incubate at 82°C for 1.2 hours to obtain a Pt nanoparticle solution.

[0070] (2) The above Pt nanoparticle solution was cooled to room temperature, 1.1 mmol Co(NO3)2·6H2O was added, and after stirring evenly, the solution was heated to 62°C, and 11 mL of 0.1 mol / L hydrazine hydrate solution (reducing agent) was added dropwise. After the addition was completed, the mixture was kept at 62°C for 1.8 hours to obtain a Pt@Co core-shell nanocluster solution.

[0071] Precautions: Wear protective equipment when using hydrazine hydrate to avoid direct contact; PEG protective agent needs to be added slowly to prevent local agglomeration; the hydrazine hydrate droplet acceleration rate needs to be controlled within 0.5mL / min to avoid violent reactions and the production of toxic gases.

[0072] Loading Pt-Co core-shell nanoclusters onto VN / CNT composite supports

[0073] (1) Weigh 1 g of the prepared VN / CNT composite support and disperse it in 50 mL of deionized water. Ultrasonicate for 35 minutes to fully disperse it. Slowly add the above Pt@Co core-shell nanocluster solution to the VN / CNT composite support dispersion and stir at 25°C for 3.5 hours. After the reaction, filter, wash with deionized water and ethanol three times respectively, and vacuum dry at 65°C for 11 hours to obtain the Pt@Co / VN-CNT catalyst.

[0074] Note: Use a gradient stirring rate (300 rpm initially, 500 rpm later) to promote uniform loading; maintain a slightly negative pressure (-0.02 MPa) during the initial stage of vacuum drying to prevent oxidation of the nanoclusters.

[0075] The CNT structure is as follows:

[0076]

[0077] Example 4

[0078] Preparation of VN / CNT composite support

[0079] (1) 5 g of CNTs were weighed and added to 200 mL of 3.5 mol / L nitric acid solution. The mixture was ultrasonically treated at 380 W for 1.6 h, filtered, washed with deionized water until neutral, and dried at 88°C for 10.5 h. The treated CNTs were dispersed in 100 mL of deionized water, and 2.3 g of NH₄VO₃, 5 g of urea, and 0.4 g of sodium citrate (structure-directing agent) were added. The mixture was stirred for 35 min to uniformly mix, and then transferred to a 200 mL autoclave and reacted at 188°C for 10.5 h.

[0080] (2) After cooling to room temperature, filtering, washing, and drying (same conditions as in Example 3) to obtain a precursor.

[0081] (3) The precursor was placed in a tubular furnace, heated to 830 °C at a heating rate of 5.8 °C / min under a nitrogen atmosphere, and calcined for 1.6 h with a nitrogen flow rate controlled at 58 mL / min to obtain a VN / CNT composite support.

[0082] Note: Sodium citrate must be completely dissolved before adding the CNT dispersion; during the high-pressure reaction, the pressure changes must be recorded every 2 hours to ensure the safety of the reactor.

[0083] Preparation of Pt-Co core-shell nanoclusters

[0084] (1) 0.52 mmol H2PtCl6·6H2O was dissolved in 50 mL deionized water, 0.105 g PVP was added, and the mixture was stirred for 12 minutes. The mixture was transferred to a microwave reactor with a power of 500 W and a temperature of 80°C. The reaction was continued for 30 minutes and then cooled to room temperature to obtain a Pt nanoparticle solution.

[0085] (2) Add 1.05 mmol Co(NO3)2·6H2O to the above solution, stir evenly and transfer it to a microwave reactor again, add 10.5 mL of 0.1 mol / L ascorbic acid solution, set the power to 450 W and the temperature to 60 °C, and react for 45 minutes to obtain a Pt@Co core-shell nanocluster solution.

[0086] Note: Before microwave reaction, make sure the reactor gasket is intact; during the reaction, monitor the temperature in real time to prevent local overheating caused by uneven microwave field; wear heat-insulating gloves when taking out the reactor.

[0087] Loading Pt-Co core-shell nanoclusters onto VN / CNT composite supports

[0088] (1) The impregnation-evaporation method was used: 1 g of VN / CNT composite support was mixed with Pt@Co core-shell nanocluster solution, stirred and evaporated to a paste in a 60 °C water bath, and then transferred to a vacuum drying oven and dried at 62 °C for 11.5 h to obtain Pt@Co / VN-CNT catalyst.

[0089] Note: During the evaporation process, continuous stirring is required to prevent local concentration from being too high; the paste material needs to be spread loosely to avoid clumping after drying.

[0090] The structure of the VN / CNT composite carrier is as follows:

[0091]

[0092]

[0093] The final catalyst Pt@Co / VN-CNT structure is as follows:

[0094]

[0095] Comparative Example 1

[0096] (1) CNT treatment: The same steps as in Example 1 are followed to obtain treated CNTs.

[0097] (2) Preparation of Pt-Co core-shell nanocluster-supported CNT catalyst: The treated CNTs were dispersed in 50 mL of deionized water and ultrasonically treated for 30 minutes. The same amount of H2PtCl6 solution and Co(NO3)2 solution as in Example 1 were added and stirred. After uniform mixing, the same amount of reducing agent NaBH4 solution was added and the mixture was allowed to react at room temperature for 2 hours. After the reaction, the mixture was filtered, washed, and dried to obtain the Pt@Co / CNT catalyst.

[0098] Comparative Example 2

[0099] (1) Preparation of VN Support: 2 g of NH₄VO₃ and 5 g of urea were weighed and dissolved in 100 mL of deionized water. The mixture was stirred and transferred to an autoclave for reaction at 180°C for 12 h. After cooling, the mixture was filtered, washed, and dried to obtain a precursor. The precursor was calcined at 800°C for 2 h under a nitrogen atmosphere to obtain a VN support.

[0100] (2) Preparation of Pt-Co core-shell nanocluster supported VN catalyst: The VN support was dispersed in 50 mL of deionized water, ultrasonicated for 30 minutes, and the same amount of H2PtCl6 solution and Co(NO3)2 solution as in Example 1 were added. After stirring, the same amount of reducing agent NaBH4 solution was added and reacted at room temperature for 2 hours. After the reaction was completed, the catalyst was filtered, washed, and dried to obtain the Pt@Co / VN catalyst.

[0101] Comparative Example 3

[0102] (1) Preparation of VN / CNT composite carrier: same as the steps in Example 1.

[0103] (2) Preparation of Pt nanoparticle-supported VN / CNT catalyst: 0.5 mmol H2PtCl6·6H2O was dissolved in 50 mL deionized water, 1 g VN / CNT composite support was added, and ultrasonic dispersion was performed for 30 min. Then, 10 mL 0.1 mol / L NaBH4 solution was added, and the mixture was stirred at room temperature for 2 h. The mixture was filtered, washed, and dried to obtain a Pt / VN-CNT catalyst.

[0104] Comparative Example 4

[0105] (1) Preparation of Co@Pt core-shell nanocluster-loaded VN / CNT catalyst: First, prepare Co nanoparticles (using Co(NO3)2·6H2O as raw material and NaBH4 as reducing agent), and then coat the surface with a Pt layer. The other steps are the same as in Example 1 to obtain a Co@Pt / VN-CNT catalyst.

[0106] Comparative Example 5

[0107] (1) Preparation of Pt-Co alloy nanoparticle-loaded VN / CNT catalyst: 0.5 mmol H2PtCl6·6H2O and 1 mmol Co(NO3)2·6H2O were added to the VN / CNT dispersion at the same time, and then reduced simultaneously with NaBH4. The other steps were the same as those in Example 1 to obtain a Pt-Co / VN-CNT alloy catalyst.

[0108] Compared with the comparative examples, the core advantage of the embodiments of the present invention lies in that the synergistic structural design of "Pt-Co core-shell nanoclusters + VN / CNT composite support" and the optimized preparation process solve the problems of low activity, poor stability, and low precious metal utilization of existing catalysts in the alkaline water electrolysis hydrogen evolution reaction. The specific advantages are as follows:

[0109] (1) Comparative Example 1 uses only CNTs as a carrier and lacks VN modification. The VN / CNT composite carrier in the embodiment not only retains the high conductivity and large specific surface area of ​​CNTs through the synergistic effect of VN and CNTs, but also promotes the adsorption-desorption equilibrium of the intermediate product (H*) of the hydrogen evolution reaction through the hydrogen affinity of VN, significantly improving the catalytic activity.

[0110] (2) Comparative Example 2 uses only VN as a carrier, whose specific surface area is much lower than that of CNT, resulting in poor dispersion of the Pt-Co core-shell nanoclusters and easy agglomeration. The introduction of CNT in the example provides a three-dimensional support framework for VN, significantly improving the dispersibility of VN and the overall specific surface area of ​​the carrier, exposing more active sites in the Pt-Co core-shell nanoclusters. At the same time, the flexible structure of CNT enhances the corrosion resistance and cyclic stability of the catalyst.

[0111] (3) Comparative Example 3 is a single Pt metal loading without the introduction of a Co shell. The Pt@Co core-shell structure in this example optimizes the Pt d-band center through the electronic effect between the Co shell and the Pt core (electron transfer from Co to Pt), reducing the adsorption energy barrier for H*. At the same time, the Co shell can act as a "co-catalyst" to promote the dissociation of H2O under alkaline conditions. Compared with a single Pt catalyst, the activity is increased by more than 30% at the same Pt ​​dosage, and the cost of using the precious metal Pt is reduced.

[0112] (4) Comparative Example 4 is a reverse core-shell structure with a Co core and a Pt shell. Although the Pt outer layer is directly exposed, its utilization rate is low, and the Co core is easily oxidized, leading to structural collapse. In this example, the Pt core and Co shell structure not only protects the Pt core from corrosion through the Co shell, but also optimizes the catalytic activity of Pt by utilizing the electronic regulation effect of Co, while reducing the exposure of Pt and improving the cycling stability by more than 2 times.

[0113] (5) Comparative Example 5 is a Pt-Co alloy structure with random arrangement of metal atoms, which cannot achieve directional electronic control and functional partitioning of the core-shell structure. The "core-shell" interface effect of the core-shell structure in the embodiment can accurately control the electronic state of the active site, so that the Pt core is responsible for the adsorption and binding of H* and the Co shell is responsible for the dissociation of H2O. The division of labor and synergy improve the reaction kinetics. However, due to the poor uniformity of the active sites in the alloy structure, the catalytic efficiency is lower than that of the core-shell structure.

[0114] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

[0115] The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An alkaline water electrolysis hydrogen evolution catalyst, characterized in that The invention comprises a composite carrier and a core-shell nanocluster loaded on the composite carrier; the composite carrier is a VN / CNT composite carrier, and the core-shell nanocluster is a Pt-Co core-shell nanocluster; the Pt-Co core-shell nanocluster has Pt as the core and Co as the shell, and the particle size of the core and shell is 1-15 nm; the VN / CNT composite carrier comprises CNT and VN nanoparticles loaded on the CNT, and the mass fraction of VN is 5%-40%.

2. The catalyst according to claim 1, characterized in that In the Pt-Co core-shell nanoclusters, the molar ratio of Pt to Co is 1:(1-3), and the shell thickness is 0.3-3 nm.

3. The catalyst according to claim 1, characterized in that The particle size of the VN nanoparticles is 3-30 nm; the length of the CNTs is 3-100 μm and the diameter is 5-100 nm.

4. The catalyst according to claim 1, characterized in that The CNTs are pretreated with an acid solution, wherein the acid solution is a nitric acid solution or a mixed solution of sulfuric acid and nitric acid, and the concentration of the acid solution is 2-5 mol / L; in the mixed solution of sulfuric acid and nitric acid, the volume ratio of sulfuric acid to nitric acid is 1:(0.5-2).

5. A method for preparing the catalyst according to claim 1, characterized in that: The following steps are involved: (1) Preparation of VN / CNT composite carrier: (101) treating the CNTs with acid, wherein the ultrasonic power of the acid treatment is 200-500 W and the treatment time is 1-3 hours; (102) The acid-treated CNTs are dispersed in a solvent, a vanadium source, a nitrogen source, and an optional auxiliary agent are added, and the mixture is subjected to a hydrothermal reaction at a temperature of 170–200 °C for 8–15 h; (103) The hydrothermal reaction product was dried and calcined at a temperature of 700–900 °C for 1–3 h to obtain a VN / CNT composite support; (2) Preparation of Pt-Co core-shell nanoclusters: (201) The platinum source is dissolved in a solvent, a protective agent is added, and after mixing, a first reducing agent is added. The reaction temperature is 70–90 °C to obtain Pt nanoparticles; (202) A cobalt source was added to the Pt nanoparticles, and after mixing, a second reducing agent was added at a reaction temperature of 50–70 °C to obtain Pt-Co core-shell nanoclusters; (3) The Pt-Co core-shell nanoclusters are loaded on a VN / CNT composite support to obtain the catalyst.

6. The preparation method according to claim 5, characterized in that (102), the vanadium source includes NH4VO3, the nitrogen source includes urea, and the auxiliary agent includes at least one of citric acid, EDTA or sodium citrate; in step (1) ③, the calcination atmosphere is a nitrogen atmosphere or a nitrogen-hydrogen mixed atmosphere, and the volume ratio of nitrogen to hydrogen in the nitrogen-hydrogen mixed atmosphere is (8-10):

1.

7. The preparation method according to claim 5, characterized in that In step (201), the platinum source includes H2PtCl6·6H2O, the protective agent includes PVP or PEG, and the first reducing agent includes NaBH4 or KBH4; in (202), the cobalt source includes Co(NO3)2·6H2O, and the second reducing agent includes ascorbic acid or hydrazine hydrate.

8. The preparation method according to claim 5, characterized in that In step (3), the stirring reaction temperature during the loading process is 20-40° C., and the reaction time is 2-5 hours; after loading, drying is performed at a drying temperature of 50-80° C. and a drying time of 8-15 hours.

9. Use of the catalyst as claimed in claim 1 in hydrogen evolution reaction by alkaline water electrolysis, characterized in that: The reaction system used is an alkaline aqueous solution, the concentration of the alkali in the alkaline aqueous solution is 0.05-2 mol / L, and the alkali includes at least one of KOH, NaOH or LiOH.

10. The use according to claim 9, characterized in that The voltage range of the reaction was 0.01-0.5 V (vs RHE).

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