Composite electro-catalytic material with built-in electric field as well as preparation method and application of composite electro-catalytic material

Abstract

The invention provides a composite electro-catalytic material with a built-in electric field and a preparation method thereof, and belongs to the technical field of electrochemical energy materials, the preparation method comprises the following steps: soaking a nickel net in a hydrochloric acid solution for ultrasonic treatment, washing with deionized water and ethanol, and drying to obtain a pretreated nickel net; soaking the pretreated nickel net in a hydrothermal solution obtained by dissolving nickel nitrate, cobalt nitrate, urea and ammonium fluoride in deionized water, and growing a uniform nickel-cobalt hydroxide nanosheet array structure on the surface of the nickel net by using a hydrothermal method; and placing the obtained nickel-cobalt nanosheet array structure in a potassium hydroxide solution containing chloroplatinic acid, uniformly depositing platinum nanoparticles on the surface of the nanosheet by a simple cyclic voltammetry, and drying to obtain the composite electrocatalytic material with the built-in electric field. The preparation method is short in synthesis period, simple in synthesis process, convenient to operate, reliable in repeatability and very suitable for large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochemical energy materials, more specifically, it relates to a composite electrocatalytic material with built-in electric field and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy, as a clean energy, has an energy density of 142 MJ / Kg, and is widely concerned due to its environmental friendliness, zero carbon dioxide emission and high energy conversion. It can not only be used as a raw material or intermediate for obtaining methane, methanol and other fuels, but also can be used for heating in life to reduce carbon emissions and minimize the greenhouse effect. Hydrogen is a promising energy carrier, and its production is a necessary prerequisite for hydrogen energy application. At present, the main hydrogen production technologies include fossil fuel hydrogen production, biomass hydrogen production, photocatalytic hydrogen production, photoelectrochemical hydrogen production and electrocatalytic hydrogen production. Due to the scarcity of fossil energy, water as a hydrogen source will have higher practical value in the long run. Among various hydrogen production technologies, water electrolysis for hydrogen production shows great application prospect due to its green friendliness and almost no pollution to the environment. Therefore, among them, electrocatalytic water electrolysis for hydrogen production is considered as the most promising strategy to achieve sustainable large-scale hydrogen production. Therefore, the development of high current density efficient water electrolysis technology is of great significance to the construction of new energy structure, and the realization of this technology requires high-efficiency electrocatalytic materials to promote the hydrogen evolution process.

[0003] The noble metals (Pt, Ir, Pd, etc.) have high water electrolysis activity due to their unfilled d electron orbitals, but their scarcity and high price limit their industrial water electrolysis application. Therefore, it is of great significance to reduce the loading of noble metals in the catalyst, improve the utilization rate of active sites of the catalyst, accelerate the hydrogen evolution kinetics of the catalyst under high current density, and realize long-term stable hydrogen production under industrial current density. SUMMARY

[0004] The purpose of the present application is to provide a composite electrocatalytic material with built-in electric field and a preparation method and application thereof. The electrocatalytic material of the present application is obtained by first hydrothermally growing a nickel-cobalt nanosheet array on a nickel mesh, and then electrodepositing platinum nanoparticles by cyclic voltammetry to obtain a composite electrocatalytic material with built-in electric field. Compared with commercially available platinum sheets and industrial Raney nickel, the electrocatalytic material has more excellent high current density hydrogen evolution performance.

[0005] To achieve the above purpose, the present application provides a preparation method of a composite electrocatalytic material with built-in electric field, comprising the following steps: Step S1, preparing a pretreated nickel mesh; Step S2, preparing a hydrothermal solution containing metal nickel and cobalt source: dissolving nickel nitrate, cobalt nitrate, urea and ammonium fluoride in deionized water to obtain a solution; Step S3, preparing the nickel-cobalt nanosheet electrocatalytic material: immersing the pretreated nickel mesh obtained in step S1 into the hydrothermal solution obtained in step S2 to obtain the nickel-cobalt nanosheet electrocatalytic material by a hydrothermal method; Step S4, preparing the electrodeposition solution containing a metal platinum source: dissolving chloroplatinic acid in a potassium hydroxide solution to obtain the electrodeposition solution; Step S5, preparing the composite electrocatalytic material with a built-in electric field: immersing the nickel-cobalt double hydroxide nanosheet obtained in step S3 into the electrodeposition solution obtained in step S4 to obtain the composite electrocatalytic material with a built-in electric field by a cyclic voltammetry electrodeposition method.

[0006] Further, in step S1, the pretreatment of the nickel mesh is as follows: after ultrasonic treatment of the nickel mesh immersed in a dilute hydrochloric acid solution, the nickel mesh is sequentially rinsed with deionized water and ethanol, and then dried to obtain the pretreated nickel mesh.

[0007] Further, the size of the nickel mesh in step S1 is 3*4 cm 2 ~5*6 cm 2 , the mesh number is 60~200 mesh; the concentration of hydrochloric acid is 0.5~2.0 mol / L -1 ; and the ultrasonic treatment time is 10~20 min.

[0008] Further, the molar ratio of the nickel nitrate, cobalt nitrate, urea and ammonium fluoride in step S2 is 1:2:(6~15):(6~15).

[0009] Further, the temperature of the hydrothermal method in step S3 is 90~150℃, and the time is 8~12h.

[0010] Further, the concentration of chloroplatinic acid in step S4 is 175~275 μmol / L, and the concentration of potassium hydroxide is 1.5~2.5 mol / L.

[0011] Further, the voltage range of the cyclic voltammetry electrodeposition in step S5 is-1.068~-1.568 V, and the deposition time is 1000~5000s.

[0012] A composite electrocatalytic material with a built-in electric field is obtained by any one of the above preparation methods.

[0013] The composite electrocatalytic material with a built-in electric field is applied to electrolysis of water.

[0014] Compared with the prior art, the present application has the following technical effects: A preparation method of a composite electrocatalytic material with built-in electric field of the present application is to use nickel mesh as the substrate, and then use hydrothermal method and electrodeposition method to build the composite electrocatalytic material with built-in electric field. In the hydrothermal process, the nickel-cobalt nanosheet array is uniformly grown on the surface of the nickel mesh, effectively increases the surface roughness and specific surface area of the nickel mesh, and provides a carrier for further electrodeposition of platinum nanoparticles, so as to successfully build a metal-carrier heterostructure, and form a strong built-in electric field effect at the contact interface between the platinum particles and the nickel-cobalt nanosheet, effectively promote the water molecule dissociation step in the alkaline hydrogen evolution process, accelerate the alkaline hydrogen evolution kinetics, and significantly improve the alkaline hydrogen evolution activity. Compared with the commercially available platinum sheet, the electrocatalytic material prepared by the present application has more excellent hydrogen evolution performance, greatly reduces the production cost of the material; at the same time, compared with the industrial Raney nickel, the electrocatalytic material has more excellent hydrogen evolution performance under large current density, and is more energy-saving. The preparation method of the present application has short synthesis cycle, simple process, easy operation, reliable repeatability, and is very suitable for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The scanning electron microscope picture of the pretreated nickel mesh prepared in example 1 of the present application; Figure 2 The scanning electron microscope picture of the composite electrocatalytic material with built-in electric field prepared in example 1 of the present application; Figure 3 The transmission electron microscope picture of the composite electrocatalytic material with built-in electric field prepared in example 1 of the present application; Figure 4 The X-ray diffraction pattern of the composite electrocatalytic material with built-in electric field prepared in example 1 of the present application; Figure 5a The ultraviolet photoelectron spectroscopy of the composite electrocatalytic material with built-in electric field prepared in example 1 of the present application; Figure 5b The work function schematic diagram of the composite electrocatalytic material with built-in electric field prepared in example 1 of the present application; Figure 6 The hydrogen evolution reaction activity comparison diagram of the composite electrocatalytic material with built-in electric field prepared in example 1 of the present application and the comparative example 1 measured in the standard three-electrode system; Figure 7 The hydrogen evolution reaction activity comparison diagram of the composite electrocatalytic material with built-in electric field prepared in examples 1-3 measured in the standard three-electrode system; Figure 8 The hydrogen evolution reaction activity comparison diagram of the hydrogen evolution electrocatalytic materials prepared in example 1 and example 4 measured in the standard three-electrode system; Figure 9The hydrogen evolution reaction activity of the hydrogen evolution electrocatalytic material prepared in Example 1 and Example 5 of the present application is measured in a standard three-electrode system.

[0016] Figure 10 The hydrogen evolution reaction activity of the hydrogen evolution electrocatalytic material prepared in Example 1 of the present application and Comparative Example 2 is measured in a standard three-electrode system.

[0017] Figure 11 The hydrogen evolution reaction activity of the hydrogen evolution electrocatalytic material prepared in Example 1 of the present application and Comparative Example 3 is measured in a standard three-electrode system. DETAILED DESCRIPTION

[0018] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clear and explicit, the present application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not intended to limit the present application.

[0019] The terms used in the embodiments of the present application are merely for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0020] The weight of the related components mentioned in the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component, therefore, as long as the content of the related components in the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiments of the present application. Specifically, the mass mentioned in the embodiments of the present application can be µg, mg, g, kg and other mass units commonly known in the biochemical field.

[0021] The first protection of the present application is a preparation method of a composite electrocatalytic material with built-in electric field, comprising the following steps: S1, preparing a pretreated nickel mesh: after ultrasonic treatment of the nickel mesh in a dilute hydrochloric acid solution, the nickel mesh is rinsed with deionized water and ethanol in sequence, and then dried to obtain a pretreated nickel mesh; and the size of the nickel mesh is 3x4 cm 2 5x6 cm 2 , the mesh number is 60-200 meshes; the concentration of hydrochloric acid is 0.5-2.0 mol / L; the ultrasonic time is 10-20 min; S2, preparing a hydrothermal solution containing a metal nickel-cobalt source: dissolving nickel nitrate, cobalt nitrate, urea and ammonium fluoride in deionized water to obtain a solution; specifically, the molar ratio of the nickel nitrate, the cobalt nitrate, the urea and the ammonium fluoride is 1:2:(6-15):(6-15); preferably, the molar ratio of the nickel nitrate, the cobalt nitrate, the urea and the ammonium fluoride can be 1:2:6:15, 1:2:10:10, 1:2:15:15.

[0022] S3, preparing a nickel-cobalt nanosheet electrocatalytic material: immersing the pretreated nickel mesh obtained in step S1 in the hydrothermal solution obtained in step S2 to obtain a nickel-cobalt nanosheet electrocatalytic material by a hydrothermal method; specifically, the temperature of the hydrothermal method is 90-150℃, and the time is 8-12h; S4, preparing an electrodeposition solution containing a metal platinum source: dissolving chloroplatinic acid in a potassium hydroxide solution to obtain an electrodeposition solution; specifically, the concentration of the chloroplatinic acid is 175-275 μmol / L, and specifically can be 275 μmol / L, 250 μmol / L, 225 μmol / L, 200 μmol / L, 175 μmol / L; the concentration of the potassium hydroxide is 1.5-2.5 mol / L, and specifically can be 1.5 mol / L, 2.0 mol / L, 2.5 mol / L; S5, preparing a composite electrocatalytic material with a built-in electric field: immersing the nickel-cobalt double hydroxide nanosheet obtained in step S3 in the electrodeposition solution obtained in step S4 to obtain a composite electrocatalytic material with a built-in electric field by cyclic voltammetry electrodeposition; specifically, the voltage range of the cyclic voltammetry electrodeposition is-1.068--1.568 V, and the deposition time is 1000-5000s, and specifically can be 1000s, 3000s, 5000s.

[0023] The second protection of the present application is the composite electrocatalytic material with a built-in electric field prepared by the above preparation method.

[0024] The third protection of the present application is the application of the composite electrocatalytic material with a built-in electric field in water electrolysis.

[0025] Example 1 The present application provides a composite electrocatalytic material with a built-in electric field and a preparation method thereof, comprising the following steps: (1) preparing a pretreated nickel mesh: cutting a commercially available nickel mesh purchased to a size of 3x4 cm 2 After that, immerse it in a 10wt% dilute hydrochloric acid solution for ultrasonic treatment for 15 minutes, take it out after ultrasonic treatment, and then sequentially clean it with deionized water and ethanol for 15 minutes, and then dry to obtain a pretreated nickel mesh; (2) Preparation of nickel-cobalt nanosheet electrocatalytic material: the pretreated nickel mesh of step (1) is placed in a solution of 1 mmol / L nickel nitrate, 2 mmol / L cobalt nitrate, 6 mmol / L urea and 15 mmol / L ammonium fluoride, and hydrothermal reaction is carried out at 150°C for 10 hours. The sample obtained after hydrothermal reaction is washed with deionized water and dried to obtain the nickel-cobalt nanosheet electrocatalytic material.

[0026] (3) Preparation of composite electrocatalytic material with built-in electric field: the nickel-cobalt nanosheet electrocatalytic material obtained in step (2) is placed in a 1 mol / L potassium hydroxide solution containing 225 μmol / L chloroplatinic acid, and cyclic voltammetry electrodeposition is carried out at a voltage range of -1.068~-1.058V for 3000s. The composite electrocatalytic material with built-in electric field is obtained after washing with deionized water and drying.

[0027] Example 2 The embodiment 2 of the present application provides a composite electrocatalytic material with built-in electric field and a preparation method thereof, comprising the following steps: (1) Preparation of pretreated nickel mesh: the commercially available nickel mesh is cut into a size of 3×4 cm 2 After that, the nickel mesh is immersed in a 10wt% dilute hydrochloric acid solution for ultrasonic treatment for 15 minutes. After ultrasonic treatment, the nickel mesh is taken out, washed with deionized water and ethanol in sequence for 15 minutes, and dried to obtain the pretreated nickel mesh. (2) Preparation of nickel-cobalt nanosheet electrocatalytic material: the pretreated nickel mesh of step (1) is placed in a solution of 1 mmol / L nickel nitrate, 2 mmol / L cobalt nitrate, 6 mmol / L urea and 15 mmol / L ammonium fluoride, and hydrothermal reaction is carried out at 150°C for 10 hours. The sample obtained after hydrothermal reaction is washed with deionized water and dried to obtain the nickel-cobalt nanosheet electrocatalytic material.

[0028] (3) Preparation of composite electrocatalytic material with built-in electric field: the nickel-cobalt nanosheet electrocatalytic material obtained in step (2) is placed in a 1 mol / L potassium hydroxide solution containing 225 μmol / L chloroplatinic acid, and cyclic voltammetry electrodeposition is carried out at a voltage range of -1.068~-1.058V for 3000s. The composite electrocatalytic material with built-in electric field is obtained after washing with deionized water and drying.

[0029] Example 3 The embodiment 3 of the present application provides a composite electrocatalytic material with built-in electric field and a preparation method thereof, comprising the following steps: (1) Preparation of pretreated nickel mesh: the commercially available nickel mesh is cut into a size of 3×4 cm 2Afterwards, immerse in 10wt% dilute hydrochloric acid solution and ultrasonic treatment for 15 minutes, take out after ultrasonic treatment, use deionized water and ethanol to sequentially ultrasonic clean for 15 minutes, and dry to obtain the pretreated nickel mesh; (2) Prepare the nickel cobalt nanosheet electrocatalytic material: place the pretreated nickel mesh in step (1) in a solution containing 1 mmol / L nickel nitrate, 2 mmol / L cobalt nitrate, 6 mmol / L urea and 15 mmol / L ammonium fluoride, and hydrothermal reaction at 150°C for 10 hours, and then wash and dry the sample obtained after hydrothermal reaction with deionized water to obtain the nickel cobalt nanosheet electrocatalytic material.

[0030] (3) Prepare the composite electrocatalytic material with built-in electric field: place the nickel cobalt nanosheet electrocatalytic material obtained in step (2) in 1 mol / L potassium hydroxide solution containing 225 μmol / L chloroplatinic acid, and perform cyclic voltammetry electrodeposition at a voltage range of -1.068~-1.058V for 5000s, and then wash and dry with deionized water to obtain the composite electrocatalytic material with built-in electric field.

[0031] Example 4 The embodiment 4 of the present application provides a nickel cobalt nanosheet electrocatalytic material and a preparation method thereof, which comprises the following steps: (1) Prepare a pretreated nickel mesh: cut the purchased commercial nickel mesh into a size of 3x4 cm 2 Afterwards, immerse in 10wt% dilute hydrochloric acid solution and ultrasonic treatment for 15 minutes, take out after ultrasonic treatment, use deionized water and ethanol to sequentially ultrasonic clean for 15 minutes, and dry to obtain the pretreated nickel mesh; (2) Prepare the nickel cobalt nanosheet electrocatalytic material: place the pretreated nickel mesh in step (1) in a solution containing 1 mmol / L nickel nitrate, 2 mmol / L cobalt nitrate, 6 mmol / L urea and 15 mmol / L ammonium fluoride, and hydrothermal reaction at 150°C for 10 hours, and then wash and dry the sample obtained after hydrothermal reaction with deionized water to obtain the nickel cobalt nanosheet electrocatalytic material.

[0032] Example 5 The embodiment 5 of the present application provides a hydrogen evolution electrocatalytic material and a preparation method thereof, which comprises the following steps: (1) Prepare a pretreated nickel mesh: cut the purchased commercial nickel mesh into a size of 3x4 cm 2 Afterwards, immerse in 10wt% dilute hydrochloric acid solution and ultrasonic treatment for 15 minutes, take out after ultrasonic treatment, use deionized water and ethanol to sequentially ultrasonic clean for 15 minutes, and dry to obtain the pretreated nickel mesh; (2) Preparation of hydrogen evolution electrocatalytic material: the pretreated nickel mesh obtained in step (1) is placed in a 1 mol / L potassium hydroxide solution containing 225 μmol / L chloroplatinic acid, and cyclic voltammetry electrodeposition is carried out at a voltage of-1.068~-1.058V for 3000s, and then the hydrogen evolution electrocatalytic material is obtained after being washed and dried with deionized water.

[0033] Comparative Example 1 The comparative example provides a preparation method of an electrocatalytic material: a commercially available nickel mesh is cut into a size of 3×4 cm -2 After that, it is immersed in a 10wt% dilute hydrochloric acid solution for ultrasonic treatment for 15 minutes, taken out after ultrasonic treatment, and then sequentially ultrasonically cleaned with deionized water and ethanol for 15 minutes, and then dried to obtain the electrocatalytic material.

[0034] Comparative Example 2 The comparative example 2 is a commercially available platinum sheet electrode.

[0035] Comparative Example 3 The comparative example 3 is a commercially available industrial Raney nickel electrode.

[0036] Figure 1 The scanning electron microscope picture of the pretreated nickel mesh prepared in the embodiment 1 of the present application is smooth without impurities.

[0037] Figure 2 The scanning electron microscope picture of the composite electrocatalytic material with built-in electric field prepared in the embodiment 1 of the present application is shown in the figure, from which it can be seen that the platinum nanoparticles are uniformly distributed on the nickel-cobalt nanosheet array grown by hydrothermal method, a typical metal-support heterostructure is constructed, and a strong built-in electric field effect is formed at the contact interface between the metal platinum and the support nickel-cobalt hydroxide.

[0038] Figure 3 The transmission electron microscope picture of the composite electrocatalytic material with built-in electric field prepared in the embodiment 1 of the present application is consistent with its scanning electron microscope picture, the platinum metal nanoparticles are uniformly distributed on the hexagonal nickel-cobalt hydroxide nanosheet, and a built-in electric field is formed at the contact interface.

[0039] Figure 4 The X-ray diffraction pattern of the composite electrocatalytic material with built-in electric field prepared in the embodiment 1 of the present application is shown, from which the characteristic peaks belonging to different crystal faces of cobalt hydroxide / nickel hydroxide and metal platinum can be obviously seen.

[0040] Figures 5a-5b The ultraviolet photoelectron spectroscopy and the work function diagram of the composite electrocatalytic material with built-in electric field prepared in the embodiment 1 of the present application are shown respectively. Figure 5a The work function can be calculated according to the secondary electron cutoff edge in the ultraviolet photoelectron spectroscopy, and the work function of the composite electrocatalytic material with built-in electric field prepared in the embodiment 1 of the present application is 4.8eV. Figure 5bThe work function value of the metal platinum can be seen, the metal platinum has larger work function compared with nickel cobalt hydroxide, so that after the contact of platinum and nickel cobalt hydroxide, the electron transfer from the carrier to the metal occurs, thereby forming the built-in electric field effect at the contact interface.

[0041] Figure 6 The hydrogen evolution reaction activity of the electrocatalytic materials of the present application example 1 and comparative example 1 is measured under the standard three-electrode system, the test temperature is room temperature, the electrolyte is 1 mol / L potassium hydroxide solution, example 1 and comparative example 1 are respectively used as the working electrode, the commercially available platinum sheet is used as the counter electrode, and mercury / mercury oxide is used as the reference electrode. Figure 6 It can be seen that the built-in electric field composite electrocatalytic material prepared in example 1 shows the optimal hydrogen evolution performance compared with the nickel mesh pretreated in comparative example 1. It is indicated that after the metal-carrier heterostructure is constructed on the surface of the nickel mesh, the hydrogen evolution performance of the nickel mesh is greatly improved, and excellent hydrogen evolution performance under large current density is exhibited.

[0042] Figure 7 The hydrogen evolution reaction activity of the electrocatalytic materials of the present application examples 1-3 is measured under the standard three-electrode system, and the test conditions are the same as above. Figure 7 It can be seen from the test results that the different deposition amounts of platinum nanoparticles have a significant influence on the hydrogen evolution performance of the electrocatalytic material, and the built-in electric field composite electrocatalytic material prepared in example 1 of the present application exhibits the most excellent hydrogen evolution activity.

[0043] Figure 8 The hydrogen evolution reaction activity of the electrocatalytic materials of the present application examples 1 and 4 is measured under the standard three-electrode system, and the test conditions are the same as above. Figure 8 It can be seen from the test results that the further deposition of platinum nanoparticles on the nickel cobalt nanosheet greatly improves the hydrogen evolution performance of the electrocatalytic material, and the built-in electric field composite electrocatalytic material prepared in example 1 of the present application exhibits the most excellent hydrogen evolution activity.

[0044] Figure 9 The hydrogen evolution reaction activity of the electrocatalytic materials of the present application examples 1 and 5 is measured under the standard three-electrode system, and the test conditions are the same as above. Figure 9 It can be seen from the test results that the further deposition of platinum nanoparticles on the nickel cobalt nanosheet compared with the electrocatalytic material obtained by directly depositing platinum nanoparticles on the surface of the nickel mesh has more excellent hydrogen evolution performance, and the built-in electric field composite electrocatalytic material prepared in example 1 of the present application exhibits the most excellent hydrogen evolution activity.

[0045] Figure 10 The hydrogen evolution reaction activity of the electrocatalytic materials of the present application examples 1 and comparative example 2 is measured under the standard three-electrode system, and the test conditions are the same as above. Figure 10As can be seen from Table 1, the built-in electric field composite electrocatalytic material prepared in Example 1 shows more excellent large current density hydrogen evolution activity than that of the commercial platinum sheet.

[0046] Figure 11 A comparison chart of the hydrogen evolution reaction activity of the electrocatalytic materials of Example 1 and Comparative Example 3 measured under a standard three-electrode system is shown in Figure 1. The test conditions are the same as above. Figure 11 As can be seen from Table 1, the built-in electric field composite electrocatalytic material prepared in Example 1 shows more excellent large current density hydrogen evolution activity than that of the commercial platinum sheet.

[0047] The above examples only express several embodiments of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a composite electrocatalytic material with built-in electric field, characterized in that, The method comprises the following steps: S1, preparing a pretreated nickel mesh; S2, preparing a hydrothermal solution containing a metal nickel-cobalt source: dissolving nickel nitrate, cobalt nitrate, urea and ammonium fluoride in deionized water to obtain a solution; S3, preparing a nickel-cobalt nanosheet electrocatalytic material: immersing the pretreated nickel mesh obtained in step S1 in the hydrothermal solution obtained in step S2, and obtaining a nickel-cobalt nanosheet electrocatalytic material by a hydrothermal method; S4, preparing an electrodeposition solution containing a metal platinum source: dissolving chloroplatinic acid in a potassium hydroxide solution to obtain an electrodeposition solution; S5, preparing a composite electrocatalytic material with a built-in electric field: immersing the nickel-cobalt double hydroxide nanosheet obtained in step S3 in the electrodeposition solution obtained in step S4, and obtaining a composite electrocatalytic material with a built-in electric field by cyclic voltammetry electrodeposition.

2. The method for preparing a composite electrocatalytic material with a built-in electric field as described in claim 1, characterized in that, In step S1, the pretreatment of the nickel mesh is as follows: after ultrasonic treatment in a dilute hydrochloric acid solution, the nickel mesh is sequentially rinsed with deionized water and ethanol, and then dried to obtain a pretreated nickel mesh.

3. The method for preparing a composite electrocatalytic material with a built-in electric field as described in claim 2, characterized in that, The size of the nickel mesh in step S1 is 3 x 4 cm 2 5 x 6 cm 2 The mesh number is 60-200 meshes; the concentration of hydrochloric acid is 0.5-2.0 mol / L; and the ultrasonic time is 10-20 min.

4. The preparation method of a composite electrocatalytic material with a built-in electric field as described in claim 1, characterized in that, In step S2, the molar ratio of the nickel nitrate, cobalt nitrate, urea and ammonium fluoride is 1:2:(6-15):(6-15).

5. The preparation method of a composite electrocatalytic material with a built-in electric field as described in claim 1, characterized in that, In step S3, the temperature of the hydrothermal method is 90-150℃, and the time is 8-12h.

6. A method for preparing a composite electrocatalytic material with a built-in electric field as described in claim 1, characterized in that, In step S4, the concentration of the chloroplatinic acid is 175-275 μmol / L, and the concentration of the potassium hydroxide is 1.5-2.5 mol / L.

7. A method for preparing a composite electrocatalytic material with a built-in electric field as described in claim 1, characterized in that, In step S5, the voltage range of the cyclic voltammetry electrodeposition is-1.068--1.568 V, and the deposition time is 1000-5000s.

8. A composite electrocatalytic material with built-in electric field, characterized in that, The method is obtained by any one of claims 1-6.

9. The use of a composite electrocatalytic material with a built-in electric field in the electrolysis of water according to claim 8.

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