CN110841687A - Nickel hydroxide thin layer coated tungsten nitride nanowire composite material and preparation method and application thereof - Google Patents

Abstract

The invention provides a nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material and a preparation method and application thereof. The nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material has a uniform nickel hydroxide thin layer. Coated on the surface of tungsten nitride nanowires, which is carried out by loading the hydrated tungsten oxide nanowire precursor on the substrate, and nitriding the hydrated tungsten oxide nanowire precursor under ammonia gas at high temperature, and then using electrochemical deposition to obtain hydrogen A thin layer of nickel oxide coats tungsten nitride nanowire composites. The preparation process of the invention is simple, the operation is easy, the cost is low, the electrocatalytic performance of the obtained composite material is improved, and the invention has the potential of large-scale application for the development of an industrial alkaline water electrolysis catalyst.

Description

A kind of nickel hydroxide thin layer coated tungsten nitride nanowire composite material and preparation method thereof with application

technical field

The invention relates to a composite material, in particular to a nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material and a preparation method and application thereof.

Background technique

The current society is facing severe energy crisis and environmental pollution. Hydrogen production by electrocatalytic water splitting is an effective way to solve the current crisis. However, in the actual process of electrocatalytic water splitting for hydrogen production, the kinetic hindrance of the hydrogen evolution reaction seriously restricts the improvement of the water splitting efficiency. Therefore, seeking an efficient hydrogen evolution electrocatalyst becomes the key to improving the efficiency. At present, platinum group noble metals are recognized as the most efficient electrocatalysts for hydrogen evolution, but these noble metal materials have little earth reserves and high preparation costs, which greatly limit their wide application. Therefore, there is an urgent need to develop efficient, stable, environmentally friendly and inexpensive electrocatalysts for hydrogen evolution.

As a member of transition metal nitrides, tungsten nitride has metal-like properties and can ensure rapid electron transfer. At the same time, the nitrogen element in tungsten nitride can adjust the electron concentration around the metal atom, thereby optimizing the adsorption and desorption of the metal atom to the reaction intermediate, so it has a good electrocatalytic hydrogen evolution activity. However, under alkaline conditions, tungsten nitride is limited by its low water adsorption and dissociation ability, which leads to the sluggish Volmer reaction, the first step of water electrolysis, which in turn affects the entire hydrogen evolution process of alkaline water electrolysis.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide a nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material to solve the problems of low water adsorption and dissociation ability of the existing alkaline electrolysis water catalyst and slow Volmer reaction.

The second purpose of the present invention is to provide a method for preparing a nickel hydroxide thin layer-coated tungsten nitride nanowire composite material.

The third object of the present invention is to provide the application of the aforementioned nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material in an alkaline hydrogen evolution electrocatalyst.

One of the objects of the present invention is achieved in this way:

A nickel hydroxide thin layer coated tungsten nitride nanowire composite material, tungsten nitride nanowires are uniformly grown on the surface of the substrate to form a self-supporting electrode structure, and the nickel hydroxide thin layer is uniformly coated on the tungsten nitride The surface of the nanowire, and the thickness of the nickel hydroxide thin layer is 3-7 nm, preferably 4-6 nm, more preferably 5 nm.

The nickel hydroxide thin layer-coated tungsten nitride nanowire composite material is prepared by the following method: first, the hydrated tungsten oxide nanowire precursor is supported on the substrate; then, the hydrated tungsten oxide nanowire precursor is placed in ammonia. High-temperature nitridation in the presence of gas to obtain tungsten nitride porous nanowires; finally, electroplating a nickel hydroxide thin layer on the surface of the tungsten nitride porous nanowires by electrochemical deposition to obtain a nickel hydroxide thin layer coated with nitrogen Tungsten nanowire composites.

When the nickel hydroxide thin layer-coated tungsten nitride nanowire composite material is used as an industrial alkaline water electrolysis catalyst, when the current density is 20 mA/cm ² , the overpotential is 170-268 mV, preferably 170 mV.

The second purpose of the present invention is achieved in this way:

A method for preparing a nickel hydroxide thin layer-coated tungsten nitride nanowire composite material, comprising the following steps:

(a) The hydrated tungsten oxide nanowire precursor is supported on the substrate;

(b) performing high-temperature nitridation of the substrate-supported hydrated tungsten oxide nanowire precursor obtained in step (a) in a calcining furnace under an ammonia atmosphere to obtain substrate-supported tungsten nitride nanowires;

(c) Electroplating a nickel hydroxide thin layer on the surface of the substrate-supported tungsten nitride nanowires obtained in step (b) by an electrochemical deposition method to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite material.

In step (a), the substrate can be selected from common substrate materials in the art, such as carbon fiber paper, nickel foam, copper foam, titanium sheet, etc. Preferably, carbon fiber paper is selected, and the size is 2×5 cm ² .

In step (a), a solvothermal method, specifically a hydrothermal synthesis method, is used to load the hydrated tungsten oxide nanowire precursor on the substrate, and the hydrothermal synthesis method can adopt the reaction temperature and reaction time known to those skilled in the art, Preferably, the reaction temperature is 150-200 °C, and the reaction time is 6-24 h; more preferably, the reaction temperature is 180 °C, and the reaction time is 16 h.

The hydrated tungsten oxide nanowire precursor can be synthesized using known raw materials and solvents. Preferably, an acidic solution containing tungsten ions is mixed with oxalic acid to obtain a transparent solution, and then ammonium sulfate is dissolved in the above solution to obtain the final reaction solution.

Optionally, the acidic solution containing tungsten ions is a solution obtained by dissolving inorganic tungstate in deionized water, and then adjusting the pH of the solution to 1.2, wherein the inorganic tungstate is sodium tungstate or tungstic acid Ammonium.

Specifically, using sodium tungstate dihydrate as a raw material and deionized water as a solvent, the two were prepared into a solution in a ratio of 12.5 mmol: 100 mL, and then hydrochloric acid was added dropwise to adjust the pH value of the solution to 1.2, and then 35 mmol oxalic acid dihydrate was dissolved in the above solution, and the solution was diluted to 250 mL, and finally 12.5 g of ammonium sulfate was added to obtain a colorless and transparent solution.

When the hydrated tungsten oxide nanowire precursor is loaded on the substrate, the obtained reaction solution is transferred into a reaction vessel, and the substrate is placed obliquely against the wall, and the hydrothermal synthesis reaction is carried out at a set temperature.

In step (b), the reaction temperature of the high-temperature nitridation is preferably 500-800 °C, more preferably 600-700 °C.

The high temperature nitriding time is preferably 30-180 min, more preferably 60-120 min.

In step (c), the electrochemical deposition adopts a three-electrode system. Specifically, the substrate-supported nickel hydroxide thin layer-coated tungsten nitride nanowire composite material is used as the working electrode, platinum is the auxiliary electrode, and Ag/AgCl is used as the parameter. Specific electrode, 0.1 moL/L nickel nitrate solution is used as the electroplating solution, the constant potential is -1 V, and the electroplating time is preferably 200-600 s.

The third purpose of the present invention is achieved in this way:

The application of the aforementioned nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material in the industrial water electrolysis catalyst, especially in the field of alkaline hydrogen evolution electrocatalysis.

When the nickel hydroxide thin layer-coated tungsten nitride nanowire composite material is used as an industrial alkaline water electrolysis catalyst, when the current density is 20 mA/cm ² , the overpotential is 170-268 mV, preferably 170 mV.

In the present invention, the hydrated tungsten oxide nanowire precursor is loaded on the substrate through solvothermal reaction, and the hydrated tungsten oxide nanowire precursor is subjected to high-temperature nitridation under ammonia gas, and then electrochemical deposition is used to obtain a nickel hydroxide thin layer covered with nitrogen Tungsten nitride nanowire composite material, the tungsten nitride nanowire in the obtained composite material grows on the surface of the substrate, and the surface is uniformly covered by a nickel hydroxide thin layer. This composite material is beneficial to enhance the water adsorption and dissociation ability on the surface of tungsten nitride, speed up the Volmer reaction process, and at the same time effectively accelerate the electron transfer rate of the internal tungsten nitride, improve the hydrogen evolution activity of the catalyst, and improve the electrocatalytic performance.

The composite material of the invention has the advantages of simple process flow, easy operation, low cost and easy mass production, and has the potential of large-scale application for the development of industrial alkaline electrolysis water catalyst.

Description of drawings

Fig. 1 is the XRD pattern of the sample prepared in Example 1, carbon fiber paper, and tungsten nitride standard sample.

FIG. 2 is the XPS chart of the sample prepared in Example 1. FIG.

FIG. 3 is a SEM image of the sample prepared in Example 1. FIG.

FIG. 4 is a TEM image of the sample prepared in Example 1. FIG.

FIG. 5 is the XRD pattern of the sample prepared in Comparative Example 1, the carbon fiber paper and the tungsten nitride standard sample.

FIG. 6 is an XPS chart of the sample prepared in Comparative Example 1. FIG.

FIG. 7 is a SEM image of the sample prepared in Comparative Example 1. FIG.

FIG. 8 is a TEM image of the sample prepared in Comparative Example 1. FIG.

FIG. 9 is the polarization curves of the samples prepared in Examples 1-9 and Comparative Example 1. FIG.

10 is the Tafel slope of the samples prepared in Example 1 and Comparative Example 1.

Detailed ways

The present invention will be further described below in conjunction with the examples, and the following examples are only for illustration and do not limit the protection scope of the present invention in any way.

The processes and methods not described in detail in the following examples are conventional methods well known in the art. The reagents used in the examples are all analytically pure or chemically pure, and can be purchased commercially or prepared by methods well known to those of ordinary skill in the art. The following embodiments all achieve the purpose of the present invention.

Example 1

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 120 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

The prepared materials were characterized and the results obtained are shown in Figures 1-4. It can be seen from Figure 1 that the tungsten nitride phase in the prepared nickel hydroxide thin layer-coated tungsten nitride nanowire composites is consistent with the WN 65-2898 of the JCPDS card, and there is no nickel hydroxide peak in the sample. It shows that the nickel hydroxide exists in an amorphous state; it can be seen from Figure 2 that the nickel element in the composite material exists in the form of Ni(OH) ₂ . It can be seen from Figures 3 to 4 that the obtained composite material is evenly loaded on the carbon fiber paper, the composite material is a nanowire-like structure, and the surface of the tungsten nitride nanowire is evenly wrapped with a thin layer of nickel hydroxide, which is a thin layer of nickel hydroxide. The thickness is about 5 nm.

Comparative Example 1

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 120 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

The prepared materials were characterized, and the obtained results are shown in Figures 5-8. It can be seen from Figure 5 that the tungsten nitride phase in the prepared carbon fiber paper-supported tungsten nitride nanowires is consistent with the WN 65-2898 of the JCPDS card. It can be seen from Figure 6 that the obtained material has a nanowire-like structure and is uniformly supported on the carbon fiber paper. It can be seen from FIG. 7 that the tungsten nitride nanowires have a porous structure. It can be seen from Figure 8 that there is no Ni element in the composite material.

Example 2

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The sample was placed in a tube furnace, heated to 500 °C at 5 °C/min under ammonia gas (flow rate 60 sccm), the holding time was 120 min, and then cooled to room temperature naturally to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 3

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 600 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 120 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 4

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The sample was placed in a tube furnace and heated to 800 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 120 min, and then cooled to room temperature naturally to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 5

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 30 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 6

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 60 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 7

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The sample was placed in a tube furnace, heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm), the holding time was 180 min, and then cooled to room temperature naturally to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 400 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 8

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 120 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 200 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 9

Dissolve 2.5 mmol of sodium tungstate dihydrate in 20 mL of deionized water to obtain a colorless and transparent solution, add hydrochloric acid dropwise to adjust the pH of the solution to 1.2 to obtain a pale yellow solution, and then add 7 mmol of oxalic acid dihydrate to the above solution, And dilute the solution to 50 mL, add 2.5 g of ammonium sulfate to obtain a colorless and transparent solution. The mixed solution was transferred into the reaction kettle, and the carbon fiber paper (2×5 cm ² ) was placed obliquely against the wall, heated to 180 °C, reacted for 16 h, and then cooled naturally. The carbon fiber paper was taken out and rinsed with deionized water. , and dried under vacuum at 60 °C for 12 h. The samples were placed in a tube furnace and heated to 700 °C at 5 °C/min under ammonia gas (flow rate 60 sccm) for 120 min, and then naturally cooled to room temperature to obtain carbon fiber paper-supported tungsten nitride nanowires.

Electrochemical deposition: A three-electrode system was used, with carbon fiber paper-supported tungsten nitride nanowires as the working electrode, platinum as the auxiliary electrode, Ag/AgCl as the reference electrode, 0.1 moL/L nickel nitrate solution as the electroplating solution, and the electrodeposition potential was - 1 V, and the electroplating time was 600 s to obtain a nickel hydroxide thin layer-coated tungsten nitride nanowire composite.

Example 10

The nickel hydroxide thin layer-coated tungsten nitride nanowire composite materials prepared in Examples 1 to 9 and the carbon fiber paper-supported tungsten nitride nanowire materials prepared in Comparative Example 1 were used for alkaline catalytic hydrogen evolution. Electrochemical characterization of the samples was performed using an electrochemical workstation, and measurements were performed using a three-electrode system. Among them, the mercury/mercury oxide electrode was used as the reference electrode, the carbon fiber paper supported tungsten nitride nanowire material or the carbon fiber paper supported nickel hydroxide thin-layer coated tungsten nitride nanowire composite material was used as the working electrode, and 1 M KOH was used as the electrolyte. . The electrochemical properties were characterized by scanning the polarization curves of the materials prepared in Examples 1 to 9 and Comparative Example 1, the scanning speed was 5 mV/s, and the test potential was converted to the standard hydrogen electrode potential. The obtained polarization curve results are shown in Figure 9. When the current density is 20 mA/ ^cm2 , the numerical results of the overpotential of each sample are shown in Table 1.

Table 1. Overpotential values for each sample at a current density of 20 mA/cm ²

As can be seen from Figure 9 and Table 1, the nickel hydroxide thin layer-coated tungsten nitride nanowire composite prepared in Example 1 has excellent electrocatalytic hydrogen production performance, when the current density is 20 mA/ ^cm2 , the overpotential value is the lowest, which is 170 mV, and the composite materials obtained in Examples 1 to 9 have better performance than the pure tungsten nitride nanowires prepared in Comparative Example 1, indicating that the uniform coating of the nickel hydroxide thin layer on the surface of the tungsten nitride has good performance. It is beneficial to greatly improve the electrocatalytic performance.

The Tafel slopes of the samples of Example 1 and Comparative Example 1 obtained from the polarization curves in Figure 9 are shown in Figure 10. It can be seen from the figure that the nickel hydroxide thin layer prepared in Example 1 is coated with tungsten nitride nanowires The Tafel slope of the composite material is 96mV/dec, and the Tafel slope of the tungsten nitride nanowire material prepared in Comparative Example 1 is 118 mV/dec. Both values are located in the Volmer reaction (120 mV/dec) and Heyrovsky reaction (40 mV/dec) /dec), indicating that both follow the Volmer-Heyrovsky reaction mechanism. At the same time, the Tafel slope of the tungsten nitride nanowire material prepared in Comparative Example 1 is closer to 120mV/dec, indicating that the sample is more limited by the Volmer reaction, while the nickel hydroxide thin layer prepared in Example 1 is coated with tungsten nitride. The nanowire composite material has a faster Volmer reaction rate. Therefore, the Volmer reaction process of the obtained nickel hydroxide thin layer-coated tungsten nitride nanowire composite material is accelerated, and the method of the present invention can be directly prepared. Catalytic properties of nickel hydroxide/tungsten nitride composites.

Claims (10)

1. The tungsten nitride nanowire composite material coated by the nickel hydroxide thin layer is characterized in that tungsten nitride nanowires uniformly grow on a substrate, the nickel hydroxide thin layer is uniformly coated on the surfaces of the tungsten nitride nanowires, and the thickness of the nickel hydroxide thin layer is 3-7 nm.

2. The nickel hydroxide thin layer coated tungsten nitride nanowire composite material as claimed in claim 1, wherein the nickel hydroxide thin layer coated tungsten nitride nanowire composite material is prepared by the following method: firstly, loading a hydrated tungsten oxide nanowire precursor on a substrate; then, performing high-temperature nitridation on the hydrated tungsten oxide nanowire precursor in an ammonia atmosphere to obtain a tungsten nitride nanowire; and finally, electroplating a nickel hydroxide thin layer on the surface of the tungsten nitride nanowire by an electrochemical deposition method to obtain the tungsten nitride nanowire composite material coated by the nickel hydroxide thin layer.

3. The preparation method of the nickel hydroxide thin layer coated tungsten nitride nanowire composite material as claimed in claim 1, characterized by comprising the following steps:

(a) loading a hydrated tungsten oxide nanowire precursor on a substrate;

(b) performing high-temperature nitridation on the substrate-loaded hydrated tungsten oxide nanowire precursor obtained in the step (a) in an ammonia atmosphere to obtain a substrate-loaded tungsten nitride nanowire;

(c) electroplating a nickel hydroxide thin layer on the surface of the substrate-supported tungsten nitride nanowire obtained in the step (b) by using an electrochemical deposition method to obtain the tungsten nitride nanowire composite material coated by the nickel hydroxide thin layer.

4. The method for preparing the nickel hydroxide thin layer coated tungsten nitride nanowire composite material according to claim 3, wherein in the step (a), the substrate is carbon fiber paper, foamed nickel, foamed copper or titanium sheet.

5. The method for preparing the nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material according to claim 3, wherein in the step (a), a hydrated tungsten oxide nanowire precursor is loaded on the substrate by a solvothermal method.

6. The method for preparing the nickel hydroxide thin layer coated tungsten nitride nanowire composite material according to claim 5, wherein a solvent in the solvothermal method is water, the reaction temperature is 150-200 ℃, and the reaction time is 6-24 hours.

7. The method for preparing the nickel hydroxide thin layer coated tungsten nitride nanowire composite material according to claim 3, wherein in the step (b), the nitriding temperature is 500-800 ℃, and the nitriding time is 30-180 min.

8. The method for preparing the nickel hydroxide thin layer coated tungsten nitride nanowire composite material according to claim 3, wherein in the step (c), the electrochemical deposition adopts a three-electrode system, the nickel hydroxide thin layer coated tungsten nitride nanowire composite material is used as a working electrode, a platinum sheet is used as an auxiliary electrode, Ag/AgCl is used as a reference electrode, a nickel nitrate solution is used as an electroplating solution, and the electroplating time is 200-600 s.

9. The use of the nickel hydroxide thin layer coated tungsten nitride nanowire composite material of claim 1 in the field of industrial alkaline electrolytic water catalysts.

10. The application of the nickel hydroxide thin-layer-coated tungsten nitride nanowire composite material in the field of industrial alkaline electrolytic water catalysts according to claim 8, characterized in that when the current density is 20 mA/cm²The overpotential is 170-268 mV.

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