Preparation method and application of vanadium-phosphorus-doped composite electrolyzed water catalyst

Abstract

The invention relates to the technical field of electrolyzed water and hydrogen energy utilization, and provides a preparation method and application of a vanadium and phosphorus doped composite electrolyzed water catalyst. Comprising the following steps: pretreating foamed nickel, carrying out a first hydrothermal reaction with ammonium vanadate and cobalt chloride hexahydrate, carrying out first gas phase phosphorization to obtain a Co-VOx-P / NF precursor, carrying out a second hydrothermal reaction with RuCl3, and finally carrying out second gas phase phosphorization to obtain the CoRu-VOx-P / NF catalyst. The vanadium-phosphorus-doped composite water electrolysis catalyst prepared by the invention presents a nanoflower-shaped surface appearance, the whole surface is uniformly wrapped with densely staggered nanoflowers, and a three-dimensional open nanoflower structure constructed by the stacked nanoflowers and nanoplates can provide more active catalytic sites.

Description

Technical Field

[0001] The present invention belongs to the technical field of water electrolysis and hydrogen energy utilization, and in particular relates to a preparation method and application of a vanadium-phosphorus doped composite water electrolysis catalyst. Background Art

[0002] Pt / C is a noble metal catalyst with excellent electrocatalytic activity in desalination and hydrogen evolution through water electrolysis. However, its low production volume and high cost severely limit its widespread industrial application. Phosphides, due to their excellent electrical conductivity and inherent metallic properties, are widely used in oxygen evolution reaction (OER) catalysts. Vanadium-based compounds, due to their excellent electrical conductivity and catalytic activity, are emerging as rising stars in both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER).

[0003] In recent years, vanadium-doped catalysts have garnered widespread attention in the field of electrocatalysis due to their nanoflower-like structure, which offers advantages such as high surface area, rich pore structure, and more exposed active sites. However, traditional nanoflower structures often lack dynamic responsiveness during reactions, making them difficult to adapt to ion migration and intermediate adsorption-desorption processes in water electrolysis systems, resulting in insufficient stability. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a preparation method and application of a vanadium-phosphorus-doped composite water electrolysis catalyst, which aims to solve the problems mentioned in the background technology.

[0005] In the first aspect, the present invention provides a method for preparing a dual-functional vanadium-phosphorus doped composite water electrolysis catalyst, comprising the following steps: pre-treating nickel foam, performing a first hydrothermal reaction with ammonium vanadate and cobalt chloride hexahydrate, and then performing a first gas phase phosphating to obtain Co-VO x -P / NF precursor, followed by a second hydrothermal reaction with RuCl3, and finally a second gas phase phosphating to obtain CoRu-VO x -P / NF catalyst.

[0006] Furthermore, the method specifically includes the following steps: Step 1: The nickel foam is washed successively in hydrochloric acid, acetone, ethanol and deionized water under ultrasonic assistance to remove surface oxides, thereby obtaining a pretreated nickel foam; Step 2: Dissolve ammonium vanadate and cobalt chloride hexahydrate in deionized water and stir magnetically until the solution is transparent and pink. Then, conduct a first hydrothermal reaction between the solution and the pretreated nickel foam to obtain a first precursor. After washing and drying, the first precursor is heated with sodium dihydrogen phosphate under inert gas to perform a first gas phase phosphating, and then naturally cool to room temperature to obtain Co-VO x -P / NF precursor; Step 3: Co-VO x The -P / NF precursor undergoes a second hydrothermal reaction with RuCl3 to obtain a second precursor. After the second precursor is washed and dried, it is heated with sodium dihydrogen phosphate under inert gas to undergo a second vapor phase phosphating, and then naturally cooled to room temperature to obtain a CoRu-VOx-P / NF catalyst.

[0007] Furthermore, in step 1, the concentration of hydrochloric acid is 3M, the washing time is 30 min, the washing time of acetone is 8 min, the washing time of ethanol is 10 min, and the washing time of deionized water is 10 min.

[0008] Furthermore, in step 2, ammonium vanadate: cobalt chloride hexahydrate: water = 0.5 mmol: 1 mmol: 30 mL.

[0009] Furthermore, in step 2, the temperature of magnetic stirring is 45° C., the first hydrothermal reaction condition is 180° C. for 12 hours, and the drying condition is 70° C. for 4 hours.

[0010] Furthermore, in step 2, the washing and drying conditions are: three ultrasonic washings with deionized water and drying at 70° C. for 4 hours.

[0011] Furthermore, in step 2, the inert gas is argon, and the first gas phase phosphating condition is heating to 300° C. at 5° C. / min and maintaining the phosphating time for 50 minutes.

[0012] Furthermore, in step three, the inert gas is argon, and the first gas phase phosphating condition is heating to 350° C. at 5° C. / min and maintaining the phosphating time for 50 minutes.

[0013] In a second aspect, the present invention provides the use of a vanadium-phosphorus doped composite water electrolysis catalyst in improving seawater desalination and enhancing the catalytic activity and stability of a hydrogen evolution catalyst.

[0014] The present invention has the following beneficial effects: (1) A low-cost, high-performance, and stable composite water electrolysis catalyst doped with vanadium phosphorus was prepared by hydrothermal reaction and gas-phase phosphating. It has broad application prospects and can be used to improve the catalytic activity and stability of seawater desalination and hydrogen evolution catalysts. The Ru-VP ternary synergy makes the vanadium phosphorus-doped composite water electrolysis catalyst have significant OER electrocatalytic activity. In this reaction, the incorporation of V and P weakens the chemical adsorption of oxygen-containing intermediates on metal atoms, which also has significant HER electrocatalytic activity. The surface hydrogen adsorption free energy is closest to zero.

[0015] (2) In the first phosphating (low temperature), the P source generated by the decomposition of sodium dihydrogen phosphate preferentially grows CoP nanothorns on the edge of the Co-VOx nanosheets, forming a "petal-spike" primary structure; in the second hydrothermal reaction, Ru 3+ Penetrating through the gaps between the nanosheets, the Co-Ru alloying is triggered during the second phosphating (high temperature), while driving the petal gaps to expand, forming a hollow nanoflower array; VO x During the phosphating process, the nanoflowers are transformed into an amorphous oxide layer, which coats the surface of the nanoflowers, forming a heterostructure of a catalytically active shell and an electron-conducting core. A secondary hydrothermal and secondary phosphating step yields a dynamically responsive nanoflower structure (hollow nanoflowers + core-shell heterostructure). This nanoflower-like surface morphology is uniformly coated with densely interlaced nanoflowers. The three-dimensional, open nanoflower structure, constructed from stacked nanoflowers and nanosheets, provides more active catalytic sites.

[0016] (3) The equipment is simple, the reaction time is short, and the operation is simple; the reaction raw materials are easily available, and the raw material and reaction costs are low, which is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings: Figure 1 This is an SEM image of the CoRu-VOx-P / NF catalyst material prepared in Example 1 of the present invention. Scale bar: 1 μm.

[0018] Figure 2 The CoRu-VOx-P / NF catalyst prepared in Example 1 of the present invention and the CoRu-VOx-P / NF catalyst prepared in Comparative Example 2 are shown in FIG. x XRD pattern of / NF catalyst.

[0019] Figure 3 a is the CoRu-VO prepared in Example 1 of the present invention x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 xFree energy diagram of each step of OER for CoP / NF catalyst and CoP / NF catalyst prepared in Comparative Example 1; Figure 3 b is the CoRu-VO prepared in Example 1 of the present invention x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x O2 adsorption energy values ​​of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1.

[0020] Figure 4 The CoRu-VO prepared in Example 1 of the present invention x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x The total state density of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1 is as follows: Figure 4 a is the CoRu-VO prepared in Example 1 x -Total density of states of P / NF catalyst; Figure 4 b is Co-VO prepared in Example 1 x -Total density of states of P / NF precursor; Figure 4 c in the figure is CoRu-VO prepared in comparative example 2 x Total density of states of / NF catalyst; Figure 4 d in is the total state density of the CoP / NF catalyst prepared in Comparative Example 1.

[0021] Figure 5 a is the CoRu-VO prepared in Example 1 x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x Free energy diagram of each step of HER for the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1; Figure 5 b is the CoRu-VO prepared in Example 1 x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x The δEv values ​​of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1 were subjected to HER. The lower the δEv, the higher the catalytic activity.

[0022] Figure 6is the OER performance in 1.0 M KOH solution, where: Figure 6 a is the CoRu-VO prepared in Example 1 x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x LSV polarization curves of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1; Figure 6 b is the CoRu-VO prepared in Example 1 x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x The CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1 were -2 and 50 mA cm -2 The corresponding overpotential.

[0023] Figure 6 c is the CoRu-VO prepared in Example 1 x -Constant current stability test of P / NF catalyst.

[0024] Figure 7 is the HER performance in 1.0 M KOH solution, where: Figure 7 a is the CoRu-VO prepared in Example 1 x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x LSV polarization curves of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1; Figure 7 b is the CoRu-VO prepared in Example 1 x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x The CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1 were -2 and 50 mA cm -2 The corresponding overpotential.

[0025] Figure 7 c is the CoRu-VO prepared in Example 1 x -Constant current stability test of P / NF catalyst. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; the terms used herein are only for the purpose of describing specific embodiments rather than limiting the present invention.

[0028] The present invention provides a method for preparing a dual-functional vanadium-phosphorus doped composite water electrolysis catalyst, comprising the following steps: pre-treating nickel foam, performing a first hydrothermal reaction with ammonium vanadate and cobalt chloride hexahydrate, and then performing a first gas phase phosphating to obtain Co-VO x -P / NF precursor, followed by a second hydrothermal reaction with RuCl3, and finally a second gas phase phosphating to obtain CoRu-VO x -P / NF catalyst.

[0029] In some embodiments, the method specifically includes the following steps: Step 1: The nickel foam is washed successively in hydrochloric acid, acetone, ethanol and deionized water under ultrasonic assistance to remove surface oxides, thereby obtaining a pretreated nickel foam; Step 2: Dissolve ammonium vanadate and cobalt chloride hexahydrate in deionized water and stir magnetically until the solution is transparent and pink. Then, conduct a first hydrothermal reaction between the solution and the pretreated nickel foam to obtain a first precursor. After washing and drying, the first precursor is heated with sodium dihydrogen phosphate under inert gas to perform a first gas phase phosphating, and then naturally cool to room temperature to obtain Co-VO x -P / NF precursor; Step 3: Co-VO x The -P / NF precursor undergoes a second hydrothermal reaction with RuCl3 to obtain a second precursor. After the second precursor is washed and dried, it is heated with sodium dihydrogen phosphate under inert gas to undergo a second vapor phase phosphating, and then naturally cooled to room temperature to obtain a CoRu-VOx-P / NF catalyst.

[0030] In some embodiments, in step 1, the concentration of hydrochloric acid is 3M, the washing time is 30 min, the washing time of acetone is 8 min, the washing time of ethanol is 10 min, and the washing time of deionized water is 10 min.

[0031] In some embodiments, in step 2, ammonium vanadate: cobalt chloride hexahydrate: water = 0.5 mmol: 1 mmol: 30 mL.

[0032] In some embodiments, in step 2, the temperature of magnetic stirring is 45° C., the first hydrothermal reaction condition is 180° C. for 12 hours, and the drying condition is 70° C. for 4 hours.

[0033] In some embodiments, in step 2, the washing and drying conditions are: three ultrasonic washings with deionized water, and drying at 70° C. for 4 hours.

[0034] In some embodiments, in step 2, the inert gas is argon, and the first gas phase phosphating condition is heating to 300° C. at a rate of 5° C. / min and maintaining the phosphating temperature for 50 minutes.

[0035] In some embodiments, in step 3, the inert gas is argon, and the first gas phase phosphating condition is heating to 350° C. at 5° C. / min and maintaining the phosphating condition for 50 minutes.

[0036] In some embodiments, the present invention provides applications of vanadium-phosphorus-doped composite water electrolysis catalysts in improving seawater desalination and enhancing the catalytic activity and stability of hydrogen evolution catalysts.

[0037] Example 1: (1) The area is 2×3cm 2 The nickel foam was pretreated to remove surface oxides by continuous washing in 3M hydrochloric acid (30 min), acetone (8 min), ethanol and deionized water (10 min) under ultrasonic assistance. Ammonium vanadate (0.5 mmol) and cobalt chloride hexahydrate (1 mmol) were dissolved in deionized water (30 mL) and magnetically stirred at 45 °C to obtain a transparent pink solution. The transparent pink solution and the pretreated nickel foam were then placed in a hydrothermal reactor to react at a hydrothermal temperature of 180 °C and a reaction time of 12 h. The nickel foam was then ultrasonically washed three times with deionized water and dried at 70 °C for 4 h. The nickel foam was then placed in a porcelain boat with 1 g of sodium dihydrogen phosphate placed upstream of the porcelain boat. The mixture was heated in a tube furnace at 5 °C min under Ar gas. -1 The heating rate was set to 300 ° C, and the phosphating time was maintained for 50 min. When the tube furnace was cooled to room temperature naturally, Co-VO x -P / NF precursor.

[0038] (2) Co-VO x The precursor of -P / NF was added with RuCl3 (0.5 mmol) and placed in a hydrothermal reactor for reaction at 180 °C for 12 h. The precursor was then ultrasonically washed three times with deionized water and dried at 70 °C for 4 h. The precursor was then placed in a porcelain boat with 1 g of sodium dihydrogen phosphate placed upstream of the porcelain boat. The precursor was heated in a tube furnace at 5 °C min under Ar gas. -1The tube furnace was heated to 350 °C at a heating rate of 100 nm and the phosphating time was maintained for 50 min. When the tube furnace was naturally cooled to room temperature, the CoRu-VOx-P / NF catalyst was obtained.

[0039] In the first phosphating (low temperature), the P source produced by the decomposition of sodium dihydrogen phosphate is preferentially generated in Co-VO x CoP nanothorns grow on the edge of the nanosheet to form a "petal-spike" primary structure; in the second hydrothermal reaction, Ru 3+ The VOx penetrates through the gaps between the nanosheets and into the interior, triggering Co-Ru alloying during a second phosphating step (at high temperature), while simultaneously driving the gaps between the petals to expand, forming a hollow nanoflower array. During the phosphating step, VOx transforms into an amorphous oxide layer that coats the nanoflower surface, forming a "catalytically active shell-electron conducting core" heterostructure. A dynamic responsive nanoflower structure (hollow nanoflower + core-shell heterostructure) is achieved through secondary hydrothermal and secondary phosphating steps.

[0040] Comparative Example 1: The area is 2×3cm 2 The nickel foam was pretreated to remove surface oxides by continuous washing in 3M hydrochloric acid (30min), acetone (8min), ethanol and deionized water (10min) with the assistance of ultrasound. Cobalt chloride hexahydrate (1 mmol) was dissolved in deionized water (30mL) and magnetically stirred at 45°C to a transparent pink solution. The transparent pink solution and the pretreated nickel foam were then placed in a hydrothermal reactor to react with the hydrothermal temperature of 180°C and the reaction time of 12h. The nickel foam with the precursor was taken out, ultrasonically washed three times with deionized water, and dried at 70°C for 4h. The nickel foam with the precursor was then placed in a porcelain boat, and 1g of sodium dihydrogen phosphate was placed upstream of the porcelain boat. In a tube furnace, the temperature was set at 5°C min under Ar gas. -1 The tube furnace was heated to 300 °C at a heating rate of 100 °C and maintained for 50 min. When the tube furnace was naturally cooled to room temperature, a CoP / NF catalyst was obtained.

[0041] Comparative Example 2 (1) The area is 2×3 cm 2The nickel foam was pretreated to remove surface oxides by continuous washing in 3M hydrochloric acid (30 min), acetone (8 min), ethanol and deionized water (10 min) under ultrasonic assistance. Ammonium vanadate (0.5 mmol) and cobalt chloride hexahydrate (1 mmol) were dissolved in deionized water (30 mL) and magnetically stirred at 45 ° C to obtain a transparent pink solution. The transparent pink solution and the pretreated nickel foam were then placed in a hydrothermal reactor to react with the hydrothermal temperature of 180 ° C and the reaction time of 12 h. The nickel foam with the precursor was then ultrasonically washed three times with deionized water and dried at 70 ° C for 4 h to obtain Co-VO x / NF precursor.

[0042] (2) Co-VO x RuCl3 (0.5 mmol) was added to the / NF precursor and placed in a hydrothermal reactor for reaction at 180 °C for 12 h. The nickel foam with the precursor was then ultrasonically washed three times with deionized water and dried at 70 °C for 4 h to obtain CoRu-VO x / NF catalyst.

[0043] Result analysis: (1) Microstructure and morphology analysis The CoRu-VO prepared in Example 1 was observed by scanning electron microscopy. x -P / NF catalyst material was analyzed, and the results are shown in Figure 1 .

[0044] from Figure 1 CoRu-VO can be observed x -P / NF catalyst has a dense and staggered nanoflower evenly wrapped on its entire surface. The three-dimensional open nanoflower structure constructed by stacking nanoflowers and nanoplates will provide more active catalytic sites. The CoRu-VO obtained after phosphating x -P / NF grows uniformly and densely on NF, and has a complex morphology, multi-layer cross-linked and densely packed nanoflowers on the surface, which increases the CoRu-VO x -The specific surface area of ​​P / NF provides the possibility of exposing more active sites. x -P / NF is different from Ru-doped CoRu-VO x -P / NF surface has more and denser nanopetals, which undoubtedly can provide more active catalytic sites for the reaction.

[0045] (2) Crystal structure and crystal form analysis The CoRu-VO prepared in Example 1 was characterized by X-ray diffraction. x -P / NF catalyst and CoRu-VO prepared in Comparative Example 2x / NF catalyst was analyzed, and the results were as follows Figure 2 shown.

[0046] from Figure 2 It can be seen that the two have similar five diffraction peaks, indicating that CoRu-VO x -P / NF and CoRu-VO x / NF has a similar crystal structure. XRD patterns show that CoRu-VO x The diffraction peaks of CoRu-VOx-P / NF are located at 34.9°, 43.6°, 44.8°, and 52.6°, corresponding to the (111), (200), (220), and (311) planes of cubic Ni (PDF# 01-1258), respectively. In addition to the obvious Ni reflections, the XRD pattern also shows very weak peaks, indicating that CoRu-VOx-P / NF is amorphous or weakly crystalline.

[0047] (3) DFT density functional theory calculations Co-VO prepared in Example 1 x -P / NF precursor and CoRu-VO x -P / NF catalyst, CoP / NF catalyst prepared in Comparative Example 1, CoRu-VO prepared in Comparative Example 2 x The OER and HER performances of the NF catalysts were calculated.

[0048] Theoretical simulations are based on the Vienna Abinitio Simulation Package (VASP), a commercial software developed by the Hafner research group at the University of Vienna, to simulate the electronic structure and molecular dynamics of materials. VASP is more accurate in calculating the solid structure of periodic materials and has broad applications in calculating material structural parameters and configurations, electronic structure, and optical properties. Due to its low computational cost and high accuracy, VASP has become one of the preferred software for research on material interfaces and material design.

[0049] The computational model is based on the computational hydrogen electrode (CHE) model proposed by Nørskov. When the Gibbs free energy is close to 0, the most excellent electrocatalytic performance will be exhibited. This is an important method for theoretically judging excellent electrochemical catalysts.

[0050] Norskov's method uses the maximum Gibbs energy (ΔGmax) as the activity determinant. This descriptor was proposed under the assumption of a rate-determining step: the slowest step should control the overall kinetics of a series of processes. However, for multistep reactions that occur at a finite number of locations, such as catalytic reactions, it has been gradually noticed in the past decade that there is no rate-determining step, but rather a rate-determining state. In other words, catalytic activity should be determined by several steps. Based on this idea, we should avoid using ΔG max , but to build some new descriptors. There are two such descriptors now, one is the reaction intermediate (G max (RI)), and the other is the virtual energy span proposed by the present invention ( ).

[0051] Co-VO prepared in Example 1 x -P / NF precursor and CoRu-VO x -P / NF catalyst, CoP / NF catalyst prepared in Comparative Example 1, CoRu-VO prepared in Comparative Example 2 x The energy values ​​of the / NF catalyst were obtained by DFT calculation as shown in Table 1 and Figure 3-Figure 5 shown.

[0052] A few notes on energy calculations: Each reaction process can be divided into several elementary steps. The Gibbs free energy change (ΔG) of each elementary step is calculated to explore the effects of V and P incorporation on atomic activity and serve as the basis for theoretical evaluation. The elementary step with the highest free energy determines the final rate of the reaction. The strength of the interaction between the catalytic active site and the reaction intermediates (OH, O, and OOH) determines the kinetics of the OER. Lower oxygen adsorption energy values ​​indicate better catalytic activity. Deeper d-band centers typically result in weaker binding between the intermediates and the catalyst surface. An efficient electrocatalyst should exhibit a bond energy close to zero for each intermediate. For the HER in alkaline environments, since H2 originates from water, water dissociation is considered a key rate-determining step. Furthermore, lower virtual energy span values ​​indicate better catalytic activity.

[0053] Table 1 DFT calculation

[0054] ①OER performance from Figure 3 As can be seen in Figure 1 and Table 1, the strong adsorption of oxygen on the catalytic site makes the formation of Co-OOH more difficult, so CoRu-VO x The maximum OER ΔG of -P / NF is between *O and *OOH, which is higher than that of CoRu-VO without P doping.x / NF is lower, which indicates that in CoRu-VO x On the surface of -P / NF, the incorporation of P greatly weakens the chemical adsorption of oxygen-containing intermediates to metal atoms. Similarly, Co-VO x -P / NF has a lower OER maximum ΔG than CoP / NF without V doping, which indicates that the x On the surface of -P / NF, the incorporation of V greatly weakens the chemical adsorption of oxygen-containing intermediates to metal atoms. The adsorption energy of oxygen in each material was analyzed by DFT calculation. Figure 3 As can be seen from b in Table 1, CoRu-VO x -P / NF has the lowest oxygen adsorption energy value, while those doped with V or P are lower than those without, which indicates that the changes in oxygen adsorption performance caused by the incorporation of V and P have a great influence on the catalyst.

[0055] from Figure 4 As can be seen from Table 1, CoRu-VO x -P / NF has the deepest d center, indicating the weakest binding strength with the intermediate, which is consistent with the free energy calculation results. DFT calculations have been used to prove that the OER reaction with CoRu-VO x Compared with CoP / NF and CoRu-VO doped with V and P, x -P / NF and Co-VO x -P / NF has higher catalytic activity.

[0056] ②HER performance from Figure 5 As can be seen from a in Table 1, CoRu-VO x After the -P / NF is modified with V and P, the ability of adsorbing Co-H (*H) and combining *H with the protons of adjacent water molecules to form H2 during water adsorption and water dissociation is greatly improved, and the barrier to H2 release is greatly reduced. x -P / NF surface dissociation energy is closest to zero. Therefore, CoRu-VO x The -P / NF surface can accelerate water dissociation and promote the formation of *H, thereby accelerating the HER reaction rate. Figure 5 As can be seen from b in Figure 1 and Table 1, CoRu-VO x -P / NF has the lowest virtual energy span value, while those doped with V or P are lower than those without, which indicates that the incorporation of V and P has a great influence on the catalyst, which is consistent with the free energy calculation results.

[0057] (4) Electrolysis water performance and stability test ①OER performance

[0058] A three-electrode system was used in a 1 M KOH solution with a scan rate of 5 mV·s -1 , the CoRu-VO prepared in Example 1 was measured x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x The electrocatalytic OER activity of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1 was measured. Figure 6 shown.

[0059] from Figure 6 As can be seen from a in CoRu-VO x -P / NF exhibits remarkable OER electrocatalytic activity.

[0060] from Figure 6 As can be seen in b, CoRu-VO x -P / NF should reach 10mA cm -2 and 50mA cm -2 The current density required is 209mV and 335mV, which is significantly lower than that of Co-VO x -P / N (284mV and 376 mV), CoRu-VO x / NF (269mV and 408mV) and CoP / NF (316mV and 418mV). 2 When CoRu-VO x -P / NF only requires 209mV overpotential, which is lower than Co-VO x -P / NF (284mV) is 75 mV lower than CoRu-VO x / NF (269 mV) is 60 mV lower and CoP / NF (316 mV) is 107 mV lower. x -P / NF catalyst also showed better catalytic performance than IrO2, RuO2, NiVIr-LDH catalyst (247mV) and NiFeV catalyst (264mV).

[0061] from Figure 6 As can be seen from the figure c, in the OER polarization potential range, the CoRu-VO x -10 mAcm on P / NF -2 The constant current test was carried out to evaluate the durability of the material through potential cycling. After 1000 potential cycles, it was found that the activity of the catalyst had basically not decayed (decay after 1000 cycles was less than 5%), which shows that CoRu-VO x-P / NF catalyst exhibits stable OER performance.

[0062] ②HER performance In 1 M KOH solution, the scan rate was 5 mV·s -1 , the CoRu-VO prepared in Example 1 was measured x -P / NF catalyst, Co-VO x -P / NF precursor, CoRu-VO prepared in Comparative Example 2 x The electrocatalytic HER activity of the CoP / NF catalyst and the CoP / NF catalyst prepared in Comparative Example 1 was measured. Figure 7 shown.

[0063] from Figure 7 As can be seen from a in CoRu-VO x -P / NF catalyst exhibits remarkable HER electrocatalytic activity.

[0064] from Figure 7 As can be seen in b, CoRu-VO x -P / NF should reach 10mA cm -2 and 50mA cm -2 The current density required is 75mV and 192mV respectively, which is significantly lower than that of Co-VO x -P / N (163mV and 277mV), CoRu-VO x / NF (232mV and 354 mV) and CoP / NF (145mV and 247 mV). x -P / NF、CoRu-VO x Compared with CoP / NF and CoRu / NF, the Ru-VP ternary synergy makes CoRu-VO x -P / NF has the highest catalytic current density and the lowest overpotential, and exhibits the best HER catalytic performance.

[0065] from Figure 7 As can be seen in c, within the HER polarization potential range, the CoRu-VO x -10mA cm on P / NF -2 The constant current test was carried out to evaluate the durability of the material through potential cycling. After 1000 potential cycles, it was found that the activity of the catalyst had basically not decayed (decay after 1000 cycles was less than 5%), which shows that CoRu-VO x -P / NF catalyst has stable HER performance.

[0066] In summary, the CoRu-VO prepared by the present invention xCompared with traditional catalysts, the P / NF catalyst has a more complex structure, a larger specific surface area, more active sites, and a more uniform phosphating growth. It has better mass transfer efficiency and anti-poisoning ability than traditional catalysts. Mass transfer efficiency is greatly improved: the hollow structure increases the electrolyte diffusion coefficient to 1.2×10 -9 m² / s, ECSA up to 24.6mF / cm²; enhanced anti-poisoning ability: amorphous VO x The shell inhibits the dissolution of Co / P, and the element loss rate is less than 3% after 100h constant current test (CoP / NF loss rate is 18%).

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite water electrolysis catalyst doped with vanadium and phosphorus, characterized in that: The following steps are involved: After the nickel foam is pretreated, it undergoes a first hydrothermal reaction with ammonium vanadate and cobalt chloride hexahydrate, and then undergoes a first gas phase phosphating to obtain Co-VO x -P / NF precursor, followed by a second hydrothermal reaction with RuCl3, and finally a second gas phase phosphating to obtain CoRu-VO x -P / NF catalyst.

2. The preparation method according to claim 1, characterized in that The specific steps include: Step 1: The nickel foam is washed successively in hydrochloric acid, acetone, ethanol and deionized water under ultrasonic assistance to remove surface oxides, thereby obtaining a pretreated nickel foam; Step 2: Dissolve ammonium vanadate and cobalt chloride hexahydrate in deionized water and stir magnetically until the solution is transparent and pink. Then, conduct a first hydrothermal reaction between the solution and the pretreated nickel foam to obtain a first precursor. After washing and drying, the first precursor is heated with sodium dihydrogen phosphate under inert gas to perform a first gas phase phosphating, and then naturally cool to room temperature to obtain Co-VO x -P / NF precursor; Step 3: Co-VO x The -P / NF precursor undergoes a second hydrothermal reaction with RuCl3 to obtain a second precursor. After the second precursor is washed and dried, it is heated with sodium dihydrogen phosphate under inert gas to undergo a second vapor phase phosphating, and then naturally cooled to room temperature to obtain a CoRu-VOx-P / NF catalyst.

3. The preparation method according to claim 2, wherein: In step 1, the concentration of hydrochloric acid is 3M, the washing time is 30 min, the washing time of acetone is 8 min, the washing time of ethanol is 10 min, and the washing time of deionized water is 10 min.

4. The preparation method according to claim 3, wherein: In step 2, ammonium vanadate: cobalt chloride hexahydrate: water = 0.5 mmol: 1 mmol: 30 mL.

5. The preparation method according to claim 4, characterized in that: In step 2, the temperature of magnetic stirring is 45° C., the first hydrothermal reaction condition is 180° C. for 12 hours, and the drying condition is 70° C. for 4 hours.

6. The preparation method according to claim 5, characterized in that: In step 2, the washing and drying conditions are: ultrasonic washing with deionized water three times and drying at 70° C. for 4 hours.

7. The preparation method according to claim 6, characterized in that: In step 2, the inert gas is argon, and the first gas phase phosphating condition is heating to 300° C. at 5° C. / min and maintaining the phosphating for 50 minutes.

8. The preparation method according to claim 6, characterized in that: In step 3, the inert gas is argon, and the first gas phase phosphating condition is heating to 350° C. at 5° C. / min and maintaining the phosphating time for 50 min.

9. A vanadium-phosphorus doped composite water electrolysis catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Application of vanadium-phosphorus doped composite water electrolysis catalysts in improving seawater desalination and enhancing the catalytic activity and stability of hydrogen evolution catalysts.

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