阅读说明：本技术 一种碳/二硫化钼-富氮氮化钼复合材料及其制备与电催化析氢应用 (Carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite material, preparation thereof and application thereof in electrocatalytic hydrogen evolution ) 是由 霍开富 皮超然 张旭明 郑洋 李星星 宋豪 于 2021-09-11 设计创作，主要内容包括：本发明公开了一种碳/二硫化钼-富氮氮化钼复合电化学催化剂材料,其制备方法包括：首先在吡咯单体的聚合过程中引入MoO-(3)纳米线,制备表面包覆聚吡咯的MoO-(3)纳米线；然后在溶剂热反应条件下,促进内核MoO-(3)纳米线溶解并与硫脲反应,在中空聚吡咯纳米管表面垂直成长二硫化钼纳米片,再进行热氮化,中空聚吡咯纳米管转化为中空碳纳米管,MoS-(2)纳米片转化为MoS-(2)-Mo-(5)N-(6),得到中空碳纳米管表面原位生长的莫特-肖特基异质结复合材料。本发明所得复合电化学催化剂材料可有效促进界面间的电子交互作用,提升催化析氢反应动力学速率,并有效提升MoS-(2)基平面的催化活性；且涉及的制备方法较简单,操作方便,适合推广应用。(The invention discloses a carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material, and a preparation method thereof comprises the following steps: firstly, introducing MoO in the polymerization process of pyrrole monomer 3 Nanowire preparation of MoO with polypyrrole coating 3 A nanowire; then promoting the inner core MoO under the condition of solvothermal reaction 3 Dissolving the nano-wire and reacting with thiourea, vertically growing a molybdenum disulfide nano-sheet on the surface of the hollow polypyrrole nanotube, and then carrying out thermal nitridation to convert the hollow polypyrrole nanotube into a hollow carbon nanotube, MoS 2 Conversion of nanosheets to MoS 2 ‑Mo 5 N 6 And obtaining the Mott-Schottky heterojunction composite material with the surface of the hollow carbon nano tube growing in situ. The composite electrochemical catalyst material obtained by the invention can effectively promote the electronic interaction between interfaces, improve the dynamic rate of the catalytic hydrogen evolution reaction and effectively improve MoS 2 Base platformCatalytic activity of the flour; and the related preparation method is simple, convenient to operate and suitable for popularization and application.)

1. The carbon/molybdenum disulfide-molybdenum nitride composite electrochemical catalyst material is characterized by comprising a carbon matrix with a hollow nanotube structure and flaky MoS which grows in situ and is vertical to the axial direction of the carbon matrix₂/Mo₅N₆Wherein MoS₂And Mo₅N₆A heterojunction is formed.

2. The carbon/molybdenum disulfide-molybdenum nitride composite electrochemical catalyst material of claim 1, wherein the hollow nanotubes have an outer diameter of 20-500nm, a wall thickness of 5-40nm, and a length of 20nm-100 μ ι η.

3. A method for preparing a carbon/molybdenum disulfide-molybdenum nitride composite electrochemical catalyst material as defined in claim 1 or 2, comprising the steps of:

1) adding MoO₃The nano-wire is dispersed in water by ultrasonic to obtain MoO₃A dispersion liquid, wherein pyrrole monomers are dropwise added into the dispersion liquid under the ice-water bath condition; then dropwise adding an oxidant solution to carry out ice-bath reaction, washing with water, and drying to obtain a polypyrrole-coated molybdenum oxide nanowire;

2) dissolving the obtained polypyrrole-coated molybdenum oxide nanowire in water, adding thiourea, uniformly mixing, carrying out hydrothermal reaction, cleaning and drying to obtain MoS₂a/PPy composite black powder;

3) the obtained MoS₂/PPy composite black powder in NH₃And carrying out heat treatment in the atmosphere to obtain the carbon/molybdenum disulfide-molybdenum nitride composite electrochemical catalyst material.

4. The method of claim 2, wherein the MoO is₃The diameter of the nano-wire is 20-500nm, and the length is 20nm-100 μm.

5. The method of claim 2, wherein the MoO is₃The dosage ratio of the monomer to the pyrrole monomer is 600-900mg:1 mL; MoO₃The mass ratio of the oxidizing agent to the oxidizing agent is 1 (2-2.5).

6. The method according to claim 2, wherein the oxidizing agent is an inorganic salt type oxidizing agent.

7. The preparation method of claim 2, wherein the ice bath temperature is 3-5 ℃; the ice-bath reaction time is 1-6 h.

8. The method of claim 2, said MoO₃The mass ratio of the nano wire to the thiourea is 1 (3-5).

9. The preparation method according to claim 2, wherein the hydrothermal reaction temperature is 180-220 ℃ and the time is 10-48 h; the heat treatment temperature is 700-800 ℃, the heating rate is 2-4 ℃/min, the ammonia gas flow is 100-300sccm, and the heat preservation time is 1-3 h.

10. The application of the carbon/molybdenum disulfide-molybdenum nitride composite electrochemical catalyst material prepared by the preparation method of any one of claims 1-2 or claims 3-9 in the field of hydrogen evolution by electrocatalysis.

Technical Field

The invention belongs to the technical field of functional materials, and particularly relates to a carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material, and preparation and application thereof in electrocatalytic hydrogen evolution.

Background

Hydrogen fuel is considered the cleanest renewable energy source and is a major alternative to fossil fuels in future energy supplies. So far, in a common hydrogen production path, the hydrogen production by decomposing water by an electrochemical catalysis method has the advantages of simplicity, high efficiency, high hydrogen production purity and the like. Meanwhile, the method can be well combined with renewable energy sources, and efficient storage and conversion of clean energy sources are realized. However, the overpotential in the electrocatalytic hydrogen production is large, resulting in high energy consumption and low efficiency. To reduce the electrical energy required to drive the electrolyzed water reaction, the use of a corresponding catalyst to reduce the surface reaction overpotential is the most effective means. The platinum-based catalyst is the most effective hydrogen production catalyst which is generally accepted at present, but the precious metal platinum has small reserves and high price, and the large-scale use of the platinum-based catalyst in the hydrogen production by water electrolysis is limited. Therefore, the development of cheap and efficient hydrogen production catalyst is of great significance.

Molybdenum disulfide, as a transition metal compound with a layered structure, has great potential in the fields of electrocatalysis, electrons and energy collection due to active sites exposed at the edge of the molybdenum disulfide, but has inert basal plane reaction activity and low conductivity due to the fact that the active sites are mostly distributed at the edge, and the time-of-arrival catalytic performance is poor; the molybdenum disulfide base plane is further modified by methods of inducing phase transformation, introducing heteroatoms, constructing a heterogeneous interface and the like so as to obtain more excellent catalytic performance.

CN201810301761.9 discloses molybdenum disulfide for a catalyst, a preparation method and application thereof, wherein in the method, a molybdenum disulfide raw material is placed in a water vapor-containing atmosphere for heating reaction, and sulfur defects are generated on a molybdenum disulfide plane through the etching effect of water vapor so as to greatly improve the catalytic activity of the molybdenum disulfide; but the resulting product has a low efficiency in catalyzing hydrogen evolution. CN201810117506.9 discloses a method for preparing a metallic transition metal sulfide nanosheet array by chemical vapor deposition; porous gold is used as a growth substrate, elemental sulfur and transition metal chloride are used as precursors, and the elemental sulfur, the transition metal chloride and the porous gold are respectively heated to different temperatures and are kept warm for a certain time to obtain corresponding catalyst products; however, the preparation cost of the method is too high, the overpotential of the single sulfide catalyst is high, and the catalytic efficiency is insufficient. CN202110140903.X discloses a preparation method of a nitrogen-doped spherical graphene-supported flaky molybdenum disulfide catalyst, which also has the problems of low catalytic hydrogen evolution efficiency and the like, and cannot adapt to industrial-level hydrogen production by electrolyzing water with high current density. The above reports of MoS2 still have the problems of low catalytic hydrogen production efficiency, high catalytic energy consumption and the like, and cannot be applied to industrial-level hydrogen production by electrolyzing water with high current density. Therefore, the development of a simple, efficient and stable molybdenum disulfide-based hydrogen production catalyst for electrolysis of water has become a problem to be solved.

Disclosure of Invention

The invention mainly aims to provide a carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material, wherein a part of molybdenum disulfide which is hydrothermally synthesized is modified in a nitriding mode, and a nitrogen-rich molybdenum nitride phase with strong adsorbability and strong catalytic activity is generated in a basal plane of molybdenum disulfide reaction inertia to form a heterojunction catalyst with high-efficiency catalytic activity; and the related preparation method is simple and is suitable for popularization and application.

In order to achieve the purpose, the invention adopts the technical scheme that:

a carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material comprises a carbon matrix with a hollow nanotube structure and flaky MoS which grows in situ and is vertical to the axial direction of the carbon matrix₂/Mo₅N₆Wherein MoS₂And Mo₅N₆Forming a heterojunction; nitrogen-rich phase Mo₅N₆The active intermediate product generated in the electrochemical process has stronger adsorption capacity, and the nitrogen-rich characteristic of the active intermediate product also can bring more excellent chemical stability; the two-phase interface structure can obviously improve the catalytic activity and the reaction kinetics of the molybdenum disulfide base plane.

In the above scheme, the MoS₂And Mo₅N₆The mass ratio of (1) to (0.2-3).

In the scheme, the outer diameter of the hollow nano tube is 20-500nm, the wall thickness is 5-40nm, and the length is 20nm-100 mu m.

The preparation method of the carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material comprises the following steps:

1) adding MoO₃The nano-wire is dispersed in water by ultrasonic to obtain MoO₃A dispersion liquid; then cooling the dispersion to 3-5 ℃ under the ice water bath condition; pyrrole (Py) was added dropwise thereto; then dropwise adding an oxidant solution to carry out ice-bath reaction, washing with water, and drying to obtain a polypyrrole-coated molybdenum oxide nanowire;

2) dissolving the obtained polypyrrole-coated molybdenum oxide nanowire in water, adding thiourea, uniformly mixing, and carrying out hydrothermal reaction, wherein the inner core MoO is generated in the process₃Dissolve and react with thiourea to form MoS₂Vertically growing on the surface of the polypyrrole nanotube, cleaning and drying to obtain MoS₂a/PPy composite black powder;

3) the obtained MoS₂/PPy composite black powder in NH₃Heat treatment is carried out under the atmosphere to carbonize the hollow polypyrrole nanotubes into hollow carbon nanotubes and MoS₂Conversion of nanosheets to MoS₂-Mo₅N₆And obtaining the carbon/molybdenum disulfide-molybdenum nitride composite electrochemical catalyst material.

In the above scheme, the MoO₃The diameter of the nanowire is 20-500nm, and the length of the nanowire is 20nm-100 mu m; synthesized by a hydrothermal method.

In the above scheme, the MoO₃In nanowire dispersion, MoO₃The concentration of the nano wire is 0.9-1.1 g/L.

In the above scheme, the MoO₃The dosage ratio of the nano-wire to the pyrrole monomer is 600-900mg:1 mL.

In the above scheme, the oxidant is an inorganic salt oxidant, and may be at least one of ammonium persulfate, ferric chloride, potassium iodate, and potassium dichromate.

In the scheme, the concentration of the oxidant solution is 7-9 mg/mL.

In the above scheme, the MoO₃The mass ratio of the nano wire to the oxidant is 1 (2-2.5).

In the scheme, the ice bath temperature is 3-5 ℃; the ice-bath reaction time is 1-6 h.

In the scheme, the mass ratio of the molybdenum oxide nanowires to the thiourea is 1 (3-5), so that the excessive thiourea is added to ensure that the vulcanization is complete.

In the scheme, the hydrothermal reaction temperature is 180-220 ℃, and the time is 10-48 h.

In the scheme, the heat treatment temperature is 700-800 ℃, the heating rate is 2-4 ℃/min, the ammonia gas flow is 100-300sccm, and the heat preservation time is 1-3 h.

The carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride nano catalytic material obtained by the invention is used as a hydrogen evolution electrocatalyst, has high electrocatalytic activity and excellent electrochemical stability under a wide pH value condition (pH is 0-14), and has excellent performance in seawater hydrogen evolution; the related preparation method is simple, low in cost and good in repetition rate, and has good application prospect in the field of hydrogen production by electrolysis.

The reaction principle of the invention is as follows:

the invention firstly uses MoO₃The preparation method comprises the following steps of preparing a polypyrrole-coated molybdenum oxide nanowire from a raw material, dissolving molybdenum oxide in an inner core of the polypyrrole nanowire in a vulcanization process, gradually dissolving the molybdenum oxide out of a surface layer of the polypyrrole to react with thiourea to generate molybdenum disulfide, forming a molybdenum disulfide sheet structure vertically growing on the surface of a hollow polypyrrole nanotube, and providing an excellent environment for electrolyte in a subsequent electrocatalysis test to enter;

then, carrying out selective nitridation treatment, wherein the reaction equation of the nitridation process is as follows:

MoS₂+4/3NH₃＝0.2Mo₅N₆+2H₂S+1/15N₂

during nitriding in ammonia atmosphere, the phenomenon that molybdenum disulfide is topologically converted into nitrogen-rich phase molybdenum nitride in a basal plane firstly occurs by adjusting nitriding temperature and controlling conditions such as heating rate, nitriding atmosphere and the like, and the phenomenon is accompanied with nitridingThe molybdenum disulfide can be finally and completely converted into nitrogen-rich phase molybdenum nitride after the time is prolonged, and finally the molybdenum disulfide composite material containing a large number of in-plane heterogeneous interfaces, namely the nitrogen-doped carbon @ nitrogen-rich phase molybdenum nitride-molybdenum sulfide composite nanowire is obtained; formed Mo₅N₆Compared with the common MoN, the method has the following advantages: 1) mo₅N₆The conductive material has excellent conductive capability and provides a charge transmission channel for electrochemical reaction; 2) mo₅N₆The characteristic of rich nitrogen has stronger adsorption effect on an active product intermediate of an electrochemical reaction, and is beneficial to carrying out water cracking reaction in an alkaline salt solution environment; 3) mo₅N₆Has stronger chemical stability.

Compared with the prior art, the invention has the beneficial effects that:

1) firstly, MoO is introduced in the polymerization process of pyrrole monomer₃Nano wire to obtain the MoO with the surface coated with polypyrrole₃Nanowires, then under solvothermal reaction conditions, promoting MoO₃Dissolving the nano-wire, reacting with thiourea to generate a molybdenum disulfide nano-sheet growing perpendicular to the surface of the hollow polypyrrole nanotube, and then carrying out thermal nitridation to obtain MoS growing in situ on the surface of the hollow carbon nanotube for the first time₂-Mo₅N₆Mott-schottky heterojunction; the hydrothermal vulcanization enables molybdenum disulfide to grow vertically on the surface of the carbon substrate, the space structure facilitates the electrolyte to enter into full reaction, more molybdenum disulfide edge plane active sites and heterogeneous interfaces on the base plane can be exposed, and the overall reaction efficiency is improved; the carbon cavity structure is used as a support carrier, so that excellent electron transfer capacity can be provided, and the electrochemical performance of the obtained composite material is remarkably improved by combining the heterojunction effect;

2) MoS formation by in-plane partial topology conversion₂-Mo₅N₆The Mott-Schottky heterojunction promotes the electronic interaction between interfaces and promotes the dynamic rate of the catalytic hydrogen evolution reaction; MoS₂In-plane-converted Mo₅N₆Improves MoS₂The adsorption capacity per se is weak, and Mo₅N₆Catalysis with self-acting as catalytic active phase also improving basal planeAnd (4) activity.

3) The preparation method provided by the invention is simple, convenient to operate and suitable for popularization and application.

Drawings

FIG. 1 is a schematic diagram of a process for preparing an electrochemical catalyst material according to the present invention;

FIG. 2 is an X-ray diffraction pattern of a final product prepared in example 1 of the present invention;

FIG. 3 is a scanning electron micrograph of a final product prepared according to example 1 of the present invention;

FIG. 4 is a transmission electron micrograph of a final product prepared according to example 1 of the present invention;

FIG. 5 is a high resolution TEM image of the final product prepared in example 1 of the present invention;

FIG. 6 is a diagram showing the electrocatalytic hydrogen evolution performance of the final product prepared in example 1 of the present invention in an acidic environment;

FIG. 7 is a graph of the electrocatalytic hydrogen evolution performance of the final product prepared in example 1 of the present invention in an alkaline environment;

FIG. 8 is a graph of the electro-catalytic hydrogen evolution performance of the final product prepared in example 1 of the present invention under a neutral environment;

FIG. 9 is a scanning electron micrograph of a final product prepared according to example 2 of the present invention;

FIG. 10 is an X-ray diffraction pattern of a final product prepared in example 2 of the present invention;

FIG. 11 is a scanning electron micrograph of a final product prepared in example 3 of the present invention;

FIG. 12 is an X-ray diffraction pattern of a final product prepared in example 3 of the present invention.

FIG. 13 is an X-ray diffraction pattern of a final product prepared in comparative example 1 of the present invention

FIG. 14 is an X-ray diffraction pattern of a final product prepared in comparative example 2 of the present invention

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the following examples, MoO was used₃The nano-wires are synthesized by a hydrothermal method described in the literature (J.Mater.chem.A,2015,3, 14617-14624); the diameter is 20-500nm, and the length is 20nm-100 μm.

Example 1

A carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material has a synthetic flow diagram shown in figure 1, and the specific preparation method comprises the following steps:

1) 320mg of MoO₃Adding 320mL of water, mixing and ultrasonically dispersing uniformly to obtain MoO₃A dispersion liquid; dissolving 650mg of ammonium persulfate in 80mL of water to prepare a uniform ammonium persulfate solution; the obtained MoO₃After the dispersion was subjected to ice-water bath treatment so that the temperature of the solution was kept at 4 ℃, 400. mu.l of pyrrole monomer (Py) was added to the dispersion, and then an ammonium persulfate solution was added dropwise; after the dropwise addition is finished, keeping the temperature of the solution for carrying out ice-water bath reaction for 5 hours (4 ℃), washing the obtained product for several times by deionized water and drying to obtain the polypyrrole-coated molybdenum oxide nanowire;

2) ultrasonically dispersing 160mg of the polypyrrole-coated molybdenum oxide nanowire in 80mL of deionized water, then adding thiourea according to the mass ratio of the nanowire to the thiourea of 1:4, uniformly mixing, transferring into a reaction kettle, carrying out hydrothermal reaction in an oven at 220 ℃ for 30 hours, washing and drying the obtained reaction product, and obtaining black powder;

3) the resulting black powder was treated with NH at a flow rate of 200sccm₃Heating to 750 ℃ at the speed of 2 ℃/min for reaction for 2 hours under the atmosphere to obtain the composite nano catalytic material (C @ Mo) with the molybdenum disulfide/molybdenum nitride heterostructure vertically grown on the surface of the inner-layer hollow carbon nanotube₅N₆-MoS₂-2h)。

FIG. 2 is an X-ray diffraction pattern of the product obtained in this example, from which XRD results Mo can be clearly seen₅N₆Generating a phase; further refining the detection result to obtain MoS₂And Mo₅N₆The mass ratio of the two phases was 1: 1.5.

FIG. 3 is a scanning electron micrograph of the product obtained in this example; it can be seen that the obtained product is a sheet-like MoS with a diameter of about 300-400nm, a length of about 20-30 μm, a hollow structure, and grown in situ perpendicular to the axial direction₂And Mo₅N₆An in-plane heterostructure having a nanosheet diameter of about 50 nm.

FIG. 4 is a transmission electron micrograph of the product obtained in this example; the scanning image is combined to show that the overall appearance of the composite material is not damaged by the nitridation process adopted by the method.

FIG. 5 is a high resolution TEM image of the product obtained in this example, from which Mo is shown₅N₆Is at MoS₂Generated in the base plane.

Fig. 6, 7 and 8 are graphs of electrocatalytic hydrogen evolution performance of the product obtained in this example under an acidic environment (pH 0.8), an alkaline environment (pH 13.8) and a neutral environment (pH 7.6), respectively, and the results show that the material obtained by this method has electrocatalytic hydrogen evolution performance comparable to Pt/C under the full pH environment, especially under the alkaline environment, and this excellent performance is of great significance for practical industrial application.

Example 2

A carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material is prepared by the following steps:

1) 320mg of MoO₃Adding 320mL of water, mixing and ultrasonically dispersing uniformly to obtain MoO₃A dispersion liquid; dissolving 650mg of ammonium persulfate in 80mL of water to prepare a uniform ammonium persulfate solution; the obtained MoO₃After the dispersion was subjected to ice-water bath treatment so that the solution temperature was maintained at 3 ℃, 400. mu.l of pyrrole monomer (Py) was added to the dispersion, and then an ammonium persulfate solution was added dropwise; after the dropwise addition is finished, keeping the temperature of the solution for 5 hours of ice-water bath reaction (3 ℃), washing the obtained product for several times by deionized water and drying to obtain the polypyrrole-coated molybdenum oxide nanowire;

2) dissolving 160mg of the obtained polypyrrole-coated molybdenum oxide nanowire in 90mL of deionized water, then adding thiourea according to the mass ratio of 1:4 of the nanowire to the thiourea, uniformly mixing, transferring into a reaction kettle, carrying out hydrothermal reaction for 36 hours in a 220 ℃ oven, and washing and drying the obtained reaction product to obtain black powder;

3) the resulting black powder was treated with NH at a flow rate of 100sccm₃Heating to 750 ℃ at the speed of 4 ℃/min and preserving the temperature for 1 hour under the atmosphere to obtain the composite nano catalytic material (C @ Mo) with the molybdenum disulfide/molybdenum nitride heterostructure vertically grown on the surface of the inner-layer hollow carbon nanotube₅N₆-MoS₂-1h)。

FIG. 9 is a scanning electron microscope image of the product obtained in this example, and it can be seen from the scanning image that the nitriding reaction in the high-temperature ammonia atmosphere has no influence on the overall structure morphology; the resulting product had a microstructure similar to that of example 1.

FIG. 10 is an X-ray diffraction pattern of the product obtained in this example from the XRD result, it can be seen that only a small amount of MoS was observed due to the nitriding time of only 1 hour₂Is nitrided into Mo₅N₆(ii) a Further refining the detection result to obtain MoS₂And Mo₅N₆The mass ratio of the two phases was 1: 0.25.

Example 3

A carbon/molybdenum disulfide-nitrogen-rich molybdenum nitride composite electrochemical catalyst material is prepared by the following steps:

1) 1mg of MoO₃Adding into 1mL water, mixing and dispersing by ultrasonic to obtain MoO₃A dispersion liquid; dissolving 650mg of ammonium persulfate in 80mL of water to prepare a uniform ammonium persulfate solution; the obtained MoO₃After the dispersion was subjected to ice-water bath treatment so that the temperature of the solution was kept at 4 ℃, 400. mu.l of pyrrole monomer (Py) was added to the dispersion, and then an ammonium persulfate solution was added dropwise to the dispersion; after the dropwise addition is finished, keeping the temperature of the solution for carrying out ice-water bath reaction for 5 hours (4 ℃), washing the obtained product for several times by deionized water and drying to obtain the polypyrrole-coated molybdenum oxide nanowire;

2) dissolving 160mg of the obtained polypyrrole-coated molybdenum oxide nanowire in 100mL of deionized water, then adding thiourea according to the mass ratio of 1:4 of the nanowire to the thiourea, uniformly mixing, transferring into a reaction kettle, carrying out hydrothermal reaction for 40 hours in a 220 ℃ oven, washing and drying the obtained reaction product, and obtaining black powder;

3) the resulting black powder was treated with NH at a flow rate of 300sccm₃Heating to 750 ℃ at the speed of 2 ℃/min for reaction for 3 hours under the atmosphere to obtain the composite nano catalytic material (C @ Mo) with the molybdenum disulfide/molybdenum nitride heterostructure vertically grown on the surface of the inner-layer hollow carbon nanotube₅N₆-MoS₂-3h)。

FIG. 11 is a scanning electron micrograph of the product obtained in this example; the resulting product had a microstructure similar to that of example 1.

FIG. 12 is an X-ray diffraction pattern of the product obtained in this example, from which it can be seen that most of MoS is observed due to the increase in nitriding time₂Is nitrided into Mo₅N₆(ii) a Further refining the detection result to obtain MoS₂And Mo₅N₆The mass ratio of the two phases was 1: 1.5.

Comparative example 1

An electrochemical catalyst material, the preparation method of which comprises the following steps:

1) 320mg of MoO₃Adding 320mL of water, mixing and ultrasonically dispersing uniformly to obtain MoO₃A dispersion liquid; dissolving 650mg of ammonium persulfate in 80mL of water to prepare a uniform ammonium persulfate solution; the obtained MoO₃After the dispersion was subjected to ice-water bath treatment so that the solution temperature was maintained at 3 ℃, 400. mu.l of pyrrole monomer (Py) was added to the dispersion, and then an ammonium persulfate solution was added dropwise to the dispersion; after the dropwise addition is finished, keeping the temperature of the solution for 5 hours of ice-water bath reaction (3 ℃), washing the obtained product for several times by deionized water and drying to obtain the polypyrrole-coated molybdenum oxide nanowire;

2) dissolving 160mg of the obtained polypyrrole-coated molybdenum oxide nanowire in 90mL of deionized water, then adding thiourea according to the mass ratio of 1:4 of the nanowire to the thiourea, uniformly mixing, transferring into a reaction kettle, carrying out hydrothermal reaction for 36 hours in a 220 ℃ oven, and washing and drying the obtained reaction product to obtain black powder;

3) the resulting black powder was subjected to a flow of 200sccmNH₃The reaction was carried out under an atmosphere at a rate of 3 ℃/min to 850 ℃ for 3 hours, and the resulting product was completely nitrided into MoN.

FIG. 13 is an X-ray diffraction pattern of the product obtained in this comparative example, which shows that molybdenum disulfide is completely converted into pure-phase MoN material after nitridation, and Mo in the invention cannot be formed₅N₆And (4) phase(s). On the other hand, the MoS reported in the Journal of Alloys and Compounds,2021,867:159066₂The over-potential of 117 mV and 132mV is respectively needed in 0.5M dilute sulfuric acid and 1M potassium hydroxide electrolyte to reach 10mA cm for the/MoN heterojunction material^-2The catalyst obtained by the invention can reach corresponding current density only by 57mV and 53mV respectively, and the nitrogen enrichment is obviously improved relative to the performance of catalytic hydrogen evolution.

Comparative example 2

An electrochemical catalyst material, the preparation method of which comprises the following steps:

1) 320mg of MoO₃Adding 320mL of water, mixing and ultrasonically dispersing uniformly to obtain MoO₃A dispersion liquid; dissolving 650mg of ammonium persulfate in 80mL of water to prepare a uniform ammonium persulfate solution; the obtained MoO₃After the dispersion was subjected to ice-water bath treatment so that the solution temperature was maintained at 3 ℃, 400. mu.l of pyrrole monomer (Py) was added to the dispersion, and then an ammonium persulfate solution was added dropwise to the dispersion; after the dropwise addition is finished, keeping the temperature of the solution for carrying out ice-water bath reaction for 5 hours (3 ℃), washing the obtained product for several times by deionized water and drying to obtain the polypyrrole-coated molybdenum oxide nanowire;

2) dissolving 160mg of the obtained polypyrrole-coated molybdenum oxide nanowire in 90mL of deionized water, then adding thiourea according to the mass ratio of 1:4 of the nanowire to the thiourea, uniformly mixing, transferring into a reaction kettle, carrying out hydrothermal reaction for 36 hours in a 220 ℃ oven, and washing and drying the obtained reaction product to obtain black powder;

3) the obtained black powder was put in a mixed atmosphere of Ar gas and ammonia gas (wherein the Ar flow rate was 200sccm, NH)₃The flow rate is 40sccm), the temperature is raised to 800 ℃ at the speed of 6 ℃/min for reaction for 3h, and the obtained products are carbon and MoS₂Composite phase of-MoN, specific XRD results are shown in figure 14.

The above embodiments are merely examples for clearly illustrating the present invention and do not limit the present invention. Other variants and modifications of the invention, which are obvious to those skilled in the art and can be made on the basis of the above description, are not necessary or exhaustive for all embodiments, and are therefore within the scope of the invention.