A high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst, a preparation method and application thereof

Abstract

The application discloses a high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst, a preparation method and application. First, nickel nitrate and ammonium molybdate are dissolved in deionized water, stirred at room temperature until dissolved, transferred to a hydrothermal kettle, and hydrothermal reaction is carried out by adding foamed nickel to obtain foamed nickel loaded with nickel molybdenum oxide nanorods. Secondly, the foamed nickel loaded with nickel molybdenum oxide nanorods is used as a precursor and is subjected to heat treatment in an atmosphere to obtain foamed nickel loaded with bimetallic nickel molybdenum compound nanorods. Finally, a mixed electrolyte of nickel nitrate and iron nitrate is prepared, the foamed nickel is added into the mixed electrolyte as a working electrode, and deposition is carried out under a constant voltage condition by using an electrochemical deposition method to obtain a heterostructure electrocatalyst. The synthesis process is simple and easy to implement, and has industrial application potential. No adhesive is used, and the in-situ grown electrode is connected with the current collector more firmly, which can meet the stability requirement of long-time operation under a large current density and can improve the performance of the catalyst.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy materials and electrochemical catalysis, and relates to a heterostructure electrocatalyst, a preparation method and application. BACKGROUND

[0002] In recent years, the energy crisis is intensifying and environmental pollution is becoming increasingly serious. Developing clean renewable energy to replace fossil fuels has far-reaching significance for sustainable economic development. Hydrogen energy, as an ideal secondary energy, has high energy density, and its combustion product is only water, which has no pollution to the environment, making it an excellent energy carrier and a future low-carbon energy alternative. Compared with hydrogen production by fossil fuels, water electrolysis has a unique advantage, but its market share is currently low. Water electrolysis is a highly efficient and clean industrial hydrogen production technology that can produce high-purity hydrogen. Water electrolysis consists of two half-reactions, namely the hydrogen evolution reaction on the cathode and the oxygen evolution reaction on the anode. Therefore, we need to explore excellent electrocatalysts to overcome the slow kinetics of these two types of electrochemical reactions. Currently, the widely used excellent performance hydrogen evolution catalysts mainly focus on noble metal Pt, and the oxygen evolution catalysts are mainly IrO2 and RuO2. These noble metals are expensive due to their low abundance in the earth's crust, and their long-term stability needs to be improved. Therefore, it is of great significance to design rationally to reduce the content of noble metals while maintaining high activity or to replace noble metals with abundant transition metals to synthesize catalysts.

[0003] Researchers have developed numerous non-noble metal-based compounds, such as sulfides, hydroxides, oxides, phosphides, borides, and single-atom catalysts, which have been reported for OER due to their adjustable electronic structures and abundant active sites. Layered double hydroxide (also known as hydrotalcite material, hereinafter referred to as LDH) is a material that is easy to prepare and has excellent electrocatalytic oxygen evolution performance. In recent years, research on hydrotalcite and its composite materials has been a hot topic, but its poor electrical conductivity has hindered further improvement of its performance. Transition metal nitride (TMN) has significantly improved electrical conductivity, enabling faster electron transport. The nitrogen element doped into the transition metal can promote the electronic structure of the nitride to approach the Fermi level, increase the electron density of the d orbit, and shrink the d band. Transition metal nitride has good corrosion resistance and electrocatalytic activity in alkaline electrolyte. Therefore, it is of great significance to develop anode oxygen evolution electrocatalysts with low cost and high activity and stability.

[0004] For industrial applications, it is essential to develop electrocatalysts with good performance under industrial relevant conditions, including high current density, long working time, and required pressure and temperature. High-performance electrocatalysts play a key role in electrochemical water splitting to reduce power consumption. In the past few decades, substantial progress has been made in the development of electrocatalysts, especially in the exploration of active sites and the development of new catalysts. However, these catalysts are usually tested under laboratory conditions (current density 1-100 mA cm -2 ). There is a large gap between the current research on electrocatalysts under low current density conditions and the practical application of water splitting technology that requires high current density. The research on high current density electrocatalysts is closely related to the practical application of water splitting technology and is an important aspect of the field of water splitting. In addition, in anion exchange membrane electrolysis cells, non-noble metal catalysts are stable and useful, and highly efficient catalysts are worth further study. Obviously, it is necessary to vigorously explore high-performance and cost-effective electrocatalysts for high current density water splitting. SUMMARY

[0005] The purpose of the present application is to provide a preparation and application of a high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst, which is used as an electrode material for electrocatalytic oxygen evolution reaction, and improves the activity of alkaline water splitting for hydrogen and oxygen production.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst, comprising the following steps:

[0008] (1) pretreat the foamed nickel to remove the surface oxide layer, then dry it for standby use;

[0009] (2) dissolve nickel nitrate and ammonium molybdate in deionized water, stir at room temperature until dissolution, transfer to an autoclave, and add the foamed nickel of step (1) as a carrier to perform hydrothermal reaction, to obtain foamed nickel loaded with nickel-molybdenum oxide nanorods; the time of the hydrothermal reaction is 4-12 h, and the reaction temperature is 120-200℃.

[0010] (3) take the foamed nickel loaded with nickel-molybdenum oxide nanorods as a precursor, and perform heat treatment in an atmosphere to obtain foamed nickel loaded with bimetallic nickel-molybdenum compound nanorods;

[0011] (4) prepare a mixed electrolyte of nickel nitrate and iron nitrate, add the foamed nickel obtained in step (3) to the mixed electrolyte as a working electrode, and perform deposition under constant voltage conditions by using electrochemical deposition method, to prepare nickel-iron bimetallic hydroxide nanosheets on the nickel-molybdenum compound nanorods, obtain a heterostructure electrocatalyst, and wash and dry it.

[0012] Preferably, in step (1), the face density of the nickel foam is 100-1000 g / m 2 , and the thickness is 0.5-2 mm; the pretreatment process is: cutting the nickel foam and then sequentially placing it in hydrochloric acid, ethanol and water for ultrasonic treatment for 10-60 min, and then drying at 40-80℃ for 2-12 h; the concentration of the hydrochloric acid is 1-5 mol / L.

[0013] Preferably, in step (2), the concentration of the nickel nitrate is 0.01-0.05 mol / L, the concentration of the ammonium molybdate is 0.01-0.05 mol / L, and the volume of the deionized water is 15-50 mL, and the stirring time is 15-30 min.

[0014] Preferably, in step (3), the heat treatment is carried out in an ammonia atmosphere at a flow rate of 60-120 sccm, at a heating rate of 4-8℃ / min to 400-650℃, and then kept for 1-3 h, and then naturally cooled to room temperature.

[0015] Preferably, in step (4), the electrochemical deposition uses a standard three-electrode system, in which the working electrode is the nickel foam loaded with the bimetallic nickel-molybdenum compound nanorod, the reference electrode is a silver / silver chloride electrode, and the counter electrode is a platinum mesh electrode.

[0016] Preferably, in step (4), the electrolyte is a mixed electrolyte of nickel nitrate and iron nitrate, in which the concentration of the nickel nitrate is 0.030-0.070 mol / L, the concentration of the iron nitrate is 0.025-0.075 mol / L, and the volume of the electrolyte is 15-30 mL.

[0017] Preferably, in step (4), a constant voltage deposition is used, in which the voltage is -0.6 to -1.2 V (relative to the silver / silver chloride electrode), and the deposition time is 80-480 s.

[0018] Preferably, in step (4), the sample is rinsed with anhydrous ethanol and deionized water for 3-5 times, and then dried in an oven at 60-80℃ for 2-12 h.

[0019] A high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst is prepared by the above method and used for the oxygen evolution reaction of water electrolysis.

[0020] When the electrocatalyst material in the application is used for the electrocatalytic oxygen evolution reaction process, the specific steps are as follows (taking NiMoN / NiFe LDH as an example): using the prepared NiMoN / NiFe LDH electrocatalyst as the working electrode, a Hg / HgO electrode as the reference electrode, and a platinum mesh as the counter electrode. The OER performance is tested in an oxygen-saturated 1 mol / L potassium hydroxide solution.

[0021] It needs to be explained that the application discloses a preparation method for synthesizing a hierarchical heterostructure electrocatalyst material through a simple and easy method, and the material has good performance in electrocatalytic decomposition of water oxygen evolution. The NiMoN / NiFe LDH hierarchical heterostructure bifunctional electrocatalyst is designed and synthesized by hydrothermal synthesis, ammoniation strategy and subsequent electrochemical deposition on a three-dimensional foam nickel substrate. The electrochemical performance test and analysis show that the NiMoN / NiFe LDH bifunctional electrocatalyst has excellent oxygen evolution and hydrogen evolution activity (in 1 mol / L potassium hydroxide solution, the OER overpotential of the NiMoN / NiFe LDH is η 500mA / cm2 = 236 mV). At the same time, it has good stability and high Faraday efficiency.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] (1) The hierarchical heterostructure electrocatalyst material in the application is synthesized by non-noble metals and does not contain noble metals, so the raw material source is wide and the cost is low; and the synthesis process is simple and easy to operate, which greatly reduces the production cost, is beneficial to large-scale production and has industrial application potential.

[0024] (2) The hierarchical heterostructure electrocatalyst material in the application is grown in situ on the current collector with high conductivity by hydrothermal reaction and electrochemical deposition method, and no adhesive is used, so it will not pollute the environment. At the same time, the in-situ grown electrode is connected with the current collector more firmly, which can meet the demand for stability of long-time operation under large current density.

[0025] (3) The electrocatalyst material in the application is a hierarchical heterostructure, and the chemical composition and micro-morphology of the catalyst material can be adjusted by controlling the reaction conditions; the construction of the heterostructure can also adjust the morphology and surface electronic structure, increase the specific surface area, ensure the full exposure of the active sites, regulate the binding energy of the adsorption intermediates and the catalyst, and thus improve the performance of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 X-ray diffraction pattern (XRD) of the electrocatalyst obtained in Example 1;

[0027] Figure 2 Scanning electron microscope (SEM) photograph of the electrocatalyst obtained in Example 1;

[0028] Figure 3 Transmission electron microscope (TEM) photograph of the electrocatalyst obtained in Example 1;

[0029] Figure 4 Electrocatalytic oxygen evolution performance graph of the electrocatalyst obtained in Example 1. DETAILED DESCRIPTION

[0030] The purposes, technical solutions and advantages of the present application will be described in detail below in combination with the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation manners and specific operation processes are given. It should be understood that the embodiments of the present application are only used to illustrate the technical effects of the present application, and are not used to limit the protection scope of the present application.

[0031] The technical solutions of the present application will be further described below in combination with embodiments.

[0032] Embodiment 1

[0033] A preparation method of a high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst includes the following steps:

[0034] (1) Blank foamed nickel (2x3 cm) is cut and ultrasonically treated in 2 mol / L hydrochloric acid, ethanol and deionized water respectively for 30 min to remove the surface oxide layer and organic impurities, and is placed in an oven for drying at 60℃ for 6 hours. After drying, it is ready for use;

[0035] (2) 0.04 mol / L nickel nitrate and 0.01 mol / L ammonium molybdate are dissolved in 15 mL deionized water, stirred at room temperature until dissolved, transferred to a 50 mL hydrothermal kettle, and the foamed nickel carrier is added. The hydrothermal temperature is set to 150℃ and the hydrothermal time is set to 6h, to obtain a foamed nickel electrocatalyst loaded with nickel-molybdenum oxide nanorods;

[0036] (3) The nickel-molybdenum oxide nanorod precursor is placed in an ammonia atmosphere for heat treatment, with the reaction temperature set to 500℃, the heating rate set to 5℃ / min, and the reaction time set to 2h, to obtain a foamed nickel loaded with bimetallic nickel-molybdenum nitride nanorods;

[0037] (4) A mixed electrolyte of 0.060 mol / L nickel nitrate and 0.048 mol / L iron nitrate is prepared, and an electrochemical deposition method is used, with a standard three-electrode system, in which the working electrode is the foamed nickel loaded with bimetallic nickel-molybdenum nitride nanorods, the reference electrode is a silver / silver chloride electrode, and the counter electrode is a platinum mesh electrode. A constant voltage deposition is adopted, with the voltage set to -1.0V (relative to the silver / silver chloride electrode) and the deposition time set to 200s. Nickel-iron bimetallic hydroxide nanosheets are prepared on the nickel-molybdenum nitride nanorods by electrodeposition, to obtain a heterostructure electrocatalyst, which is then rinsed with ethanol and deionized water for 3 times in succession, and is placed in an oven for drying at 60℃ for 12h.

[0038] When used in the process of electrocatalytic oxygen evolution reaction, the specific steps are as follows: the prepared NiMoN / NiFe LDH electrocatalyst is used as the working electrode, the Hg / HgO electrode is used as the reference electrode, and the platinum mesh is used as the counter electrode. The OER performance is tested in an oxygen-saturated 1 mol / L potassium hydroxide solution.

[0039] Structural analysis

[0040] Figure 1 X-ray diffraction pattern (XRD) of the prepared NiMoN / NiFe LDH electrocatalyst, from Figure 1 It can be seen that, in addition to the derived peaks of 44.5 degrees, 518. degrees and 76.4 degrees belonging to the foam nickel, the NiMoN / NiFe LDH electrocatalyst shows two derived peaks near 36.5 degrees and 65.7 degrees, respectively, belonging to the (100) and (110) two crystal faces of Ni 0.2 Mo 0.8 N. No derived peaks belonging to NiFe LDH were found, indicating that the NiFe LDH synthesized on the surface of NiMoN by electrochemical deposition method is amorphous structure.

[0041] Figure 2 Scanning electron microscope (SEM) of the prepared NiMoN / NiFe LDH electrocatalyst, from Figure 2 It can be seen that the NiMoN / NiFe LDH electrocatalyst is a three-dimensional hierarchical heterostructure composed of one-dimensional NiMoN nanorods loaded with two-dimensional NiFe LDH nanosheets. The diameter of the NiMoN nanorod is about 0.5 microns, and the length is about several microns, and the NiFe LDH nanosheets are uniformly distributed on the surface of the NiMoN nanorod. This hierarchical heterostructure increases the electrochemical active specific surface area, exposes more active sites, and improves the electrocatalytic activity of the catalyst.

[0042] Figure 3 Transmission electron microscope (TEM) of the prepared NiMoN / NiFe LDH electrocatalyst, from Figure 3 It can be seen that the NiMoN / NiFe LDH electrocatalyst is composed of core-shell structure with NiMoN nanorod as core layer and NiFe LDH nanosheet as shell layer, which is consistent with the SEM result. The thickness of the NiFe LDH nanosheet layer is about 50 nm, and the introduction of two-dimensional structure makes the active sites fully exposed.

[0043] Electrochemical performance test

[0044] Figure 4 Electrocatalytic oxygen evolution performance diagram of the prepared NiMoN / NiFe LDH electrocatalyst, OER linear sweep voltammetry curve in 1.0 mol / L potassium hydroxide electrolyte with a scan rate of 2 millivolts per second. From Figure 4 It can be seen from the linear voltammogram in that the NiMoN / NiFe LDH electrocatalyst has excellent oxygen evolution performance, especially at high current density, reaching 500 mA cm -2At an industrial current density of 1000 A / m2, only 236 mV overpotential is required.

[0045] Example 2

[0046] A preparation method of a high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst comprises the following steps:

[0047] (1) Cut blank foamed nickel (2x3 cm) and use 2 mol / L hydrochloric acid, ethanol and deionized water respectively for ultrasonic treatment for 30 min to remove the surface oxide layer and organic impurities, and then put them into an oven for drying at 60 DEG C for 6 hours, and then store them for later use;

[0048] (2) Dissolve 0.01 mol / L nickel nitrate and 0.05 mol / L ammonium molybdate in 15 mL deionized water, stir until dissolved at room temperature, transfer to a 50 mL hydrothermal kettle, and add the foamed nickel carrier, set the hydrothermal temperature to 120 DEG C and the hydrothermal time to 12 h, and obtain a foamed nickel electrocatalyst loaded with nickel-molybdenum oxide nanorods;

[0049] (3) Put the nickel-molybdenum oxide nanorod precursor into an ammonia atmosphere for heat treatment, set the reaction temperature to 500 DEG C, the heating rate to 5 DEG C / min, and the reaction time to 2 h, and obtain a foamed nickel loaded with bimetallic nickel-molybdenum nitride nanorods;

[0050] (4) Prepare a mixed electrolyte of 0.060 mol / L nickel nitrate and 0.048 mol / L iron nitrate, use an electrochemical deposition method, and use a standard three-electrode system, wherein the working electrode is the foamed nickel loaded with bimetallic nickel-molybdenum nitride nanorods, the reference electrode is a silver / silver chloride electrode, and the counter electrode is a platinum mesh electrode; adopt constant voltage deposition, wherein the voltage is -1.0 V (relative to the silver / silver chloride electrode), and the deposition time is 200 s, and deposit nickel-iron bimetallic hydroxide nanosheets on the nickel-molybdenum nitride nanorods to obtain a heterostructure electrocatalyst, and then wash it with ethanol and deionized water for 3 times, and then put it into an oven for drying at 60 DEG C for 12 h.

[0051] Example 3

[0052] A preparation method of a high-efficiency bimetallic nitride / hydroxide heterostructure electrocatalyst comprises the following steps:

[0053] (1) Cut blank foamed nickel (2x3 cm) and use 2 mol / L hydrochloric acid, ethanol and deionized water respectively for ultrasonic treatment for 30 min to remove the surface oxide layer and organic impurities, and then put them into an oven for drying at 60 DEG C for 6 hours, and then store them for later use;

[0054] (2) 0.05 mol / L nickel nitrate and 0.01 mol / L ammonium molybdate were dissolved in 15 mL of deionized water, stirred at room temperature until dissolved, transferred to a 50 mL hydrothermal kettle, and the nickel foam carrier was added. The hydrothermal temperature was set to 200°C and the hydrothermal time was set to 4 h to obtain a nickel-molybdenum oxide nanorod-loaded nickel foam electrocatalyst;

[0055] (3) The nickel-molybdenum oxide nanorod precursor was placed in an ammonia atmosphere for heat treatment. The reaction temperature was set to 500°C, the heating rate was 5°C / min, and the reaction time was 2 h to obtain a bimetallic nickel-molybdenum nitride nanorod-loaded nickel foam;

[0056] (4) A mixed electrolyte of 0.060 mol / L nickel nitrate and 0.048 mol / L iron nitrate was prepared. An electrochemical deposition method was used with a standard three-electrode system, in which the working electrode was a bimetallic nickel-molybdenum nitride nanorod-loaded nickel foam, the reference electrode was a silver / silver chloride electrode, and the counter electrode was a platinum mesh electrode. Constant voltage deposition was used, with a voltage of -1.0 V (relative to the silver / silver chloride electrode) and a deposition time of 200 s. Nickel-iron bimetallic hydroxide nanosheets were electrodeposited on the nickel-molybdenum nitride nanorods to obtain a heterostructure electrocatalyst, which was then rinsed with ethanol and deionized water for 3 times in succession and placed in an oven at 60°C for drying for 12 h.

[0057] Example 4

[0058] A highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst was prepared, including the following steps:

[0059] (1) Blank nickel foam (2 x 3 cm) was cut and treated with 2 mol / L hydrochloric acid, ethanol, and deionized water for 30 min each under ultrasonic treatment to remove the surface oxide layer and organic impurities. The treated nickel foam was then placed in an oven at 60°C for drying for 6 h and was ready for use after drying;

[0060] (2) 0.04 mol / L nickel nitrate and 0.01 mol / L ammonium molybdate were dissolved in 15 mL of deionized water, stirred at room temperature until dissolved, transferred to a 50 mL hydrothermal kettle, and the nickel foam carrier was added. The hydrothermal temperature was set to 150°C and the hydrothermal time was set to 6 h to obtain a nickel-molybdenum oxide nanorod-loaded nickel foam electrocatalyst;

[0061] (3) The nickel-molybdenum oxide nanorod precursor was placed in an ammonia atmosphere for heat treatment. The reaction temperature was set to 400°C, the heating rate was 5°C / min, and the reaction time was 3 h to obtain a bimetallic nickel-molybdenum nitride nanorod-loaded nickel foam;

[0062] (4) A mixed electrolyte of 0.030 mol / L nickel nitrate and 0.075 mol / L iron nitrate was prepared, and an electrochemical deposition method was used with a standard three-electrode system, in which the working electrode was a foam nickel loaded with molybdenum oxide supported nickel-molybdenum alloy nanorods, the reference electrode was a silver / silver chloride electrode, and the counter electrode was a platinum mesh electrode; a constant voltage deposition was adopted, in which the voltage was -1.0 V (relative to the silver / silver chloride electrode), and the deposition time was 480 s; nickel-iron bimetallic hydroxide nanosheets were prepared on the nickel-molybdenum compound nanorods by electrodeposition to obtain a heterogeneous structure electrocatalyst, which was continuously rinsed with ethanol and deionized water for 3 times, and was placed in an oven at 60°C for drying for 12 h.

[0063] Example 5

[0064] A preparation of an efficient bimetallic nitride / hydroxide heterogeneous structure electrocatalyst, comprising the following steps:

[0065] (1) Blank foam nickel (2x3 cm) was cut and ultrasonically treated in 2 mol / L hydrochloric acid, ethanol and deionized water for 30 min respectively to remove the surface oxide layer and organic impurities, and was placed in an oven at 60°C for drying for 6 hours, and was used after drying;

[0066] (2) 0.04 mol / L nickel nitrate and 0.01 mol / L ammonium molybdate were dissolved in 15 mL deionized water, stirred at room temperature until dissolved, transferred to a 50 mL hydrothermal kettle, and the foam nickel carrier was added, the hydrothermal temperature was set to 150°C, and the hydrothermal time was set to 6 h, to obtain a foam nickel electrocatalyst loaded with nickel-molybdenum oxide nanorods;

[0067] (3) The nickel-molybdenum oxide nanorod precursor was heat treated in an argon atmosphere, the reaction temperature was set to 650°C, the heating rate was 5°C / min, and the reaction time was 1 h, to obtain a foam nickel loaded with nickel-molybdenum oxide nanorods;

[0068] (4) A mixed electrolyte of 0.070 mol / L nickel nitrate and 0.025 mol / L iron nitrate was prepared, and an electrochemical deposition method was used with a standard three-electrode system, in which the working electrode was a foam nickel loaded with nickel-molybdenum oxide nanorods, the reference electrode was a silver / silver chloride electrode, and the counter electrode was a platinum mesh electrode; a constant voltage deposition was adopted, in which the voltage was -1.0 V (relative to the silver / silver chloride electrode), and the deposition time was 80 s; nickel-iron bimetallic hydroxide nanosheets were prepared on the nickel-molybdenum compound nanorods by electrodeposition to obtain a heterogeneous structure electrocatalyst, which was continuously rinsed with ethanol and deionized water for 3 times, and was placed in an oven at 60°C for drying for 12 h.

[0069] The above descriptions and explanations of the embodiments are to facilitate those skilled in the art to implement and use the invention,

[0070] Those skilled in the art can easily make various modifications to these embodiments and apply the general principles of this description to other embodiments without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the above embodiments, and the changes, simplifications, modifications and the like made by those skilled in the art according to the inspiration of the present application without departing from the category of the present application should be within the protection scope of the present application.

Claims

1. A method for preparing a highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst, characterized in that, Includes the following steps: Step (1) Pre-treat the nickel foam by removing the surface oxide layer and then drying it; In step (2), nickel nitrate and ammonium molybdate are dissolved in deionized water and stirred at room temperature until dissolved. The solution is then transferred to a hydrothermal reactor, and the nickel foam from step (1) is added as a carrier to carry out a hydrothermal reaction to obtain nickel foam loaded with nickel-molybdenum oxide nanorods. The thermal reaction time is 4-12 h, and the reaction temperature is 120-200 ℃. The concentration of nickel nitrate in step (2) is 0.01-0.05 mol / L, the concentration of ammonium molybdate is 0.01-0.05 mol / L, and the stirring time is 15-30 min. Step (3) Nickel foam with nickel molybdenum oxide nanorods is used as a precursor and placed in an atmosphere for heat treatment to obtain nickel foam loaded with bimetallic nickel molybdenum compound nanorods; the heat treatment temperature is 400~650 ℃. Step (4) Prepare a mixed electrolyte of nickel nitrate and ferric nitrate. Add the nickel foam obtained in step (3) to the mixed electrolyte as the working electrode. Use electrochemical deposition to deposit nickel-iron bimetallic hydroxide nanosheets on nickel-molybdenum compound nanorods under constant voltage conditions to obtain a heterostructure electrocatalyst. In the mixed electrolyte, the concentration of nickel nitrate is 0.030~0.070 mol / L and the concentration of ferric nitrate is 0.025~0.075 mol / L.

2. The method for preparing a highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst according to claim 1, characterized in that, In step (1), the areal density of the nickel foam is 100~1000 g / m³. 2 The thickness is 0.5~2mm; the pretreatment process is as follows: the cut nickel foam is placed in hydrochloric acid, ethanol and water in sequence and ultrasonicated for 10~60 min respectively, and then dried at 40~80 ℃ for 2~12 h; the concentration of hydrochloric acid is 1~5 mol / L.

3. The method for preparing a highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst according to claim 1, characterized in that, In step (3), the heat treatment is carried out in an ammonia atmosphere of 60~120 sccm at a heating rate of 4~8 ℃ / min to the heat treatment temperature, and held for 1~3 h, and then naturally cooled to room temperature.

4. The method for preparing a highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst according to claim 1, characterized in that, In step (4), electrochemical deposition uses a standard three-electrode system, in which the working electrode is nickel foam loaded with bimetallic nickel-molybdenum compound nanorods, the reference electrode is a silver / silver chloride electrode, and the counter electrode is a platinum mesh electrode.

5. The method for preparing a highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst according to claim 1, characterized in that, In step (4), the volume of the mixed electrolyte is 15~30 mL.

6. The method for preparing a highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst according to claim 1, characterized in that, In step (4), constant voltage deposition is used, with a voltage of -0.6 to -1.2 V and a deposition time of 80 to 480 s.

7. A highly efficient bimetallic nitride / hydroxide heterostructure electrocatalyst, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The application of the bimetallic nitride / hydroxide heterostructure electrocatalyst according to claim 7, characterized in that, It is applied to the oxygen evolution reaction in water electrolysis.

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