阅读说明：本技术 一种钨钼基氮碳化物纳米材料及其制备方法与应用 (Tungsten-molybdenum-based nitrogen carbide nano material and preparation method and application thereof ) 是由 王吉德 冯超 谢月洪 李世昂 张莉 陈廷祥 于 2021-01-20 设计创作，主要内容包括：本发明公开了一种钨钼基氮碳化物纳米材料及其制备方法与应用,本发明采用封装策略将磷钨酸水合物和磷钼酸水合物作为活性物种引入到铜基金属有机骨架化合物中,制备了具有纳米八面体封装结构的钨钼基纳米材料,然后通过高温下与三聚氰胺或双氰胺发生的气相沉积反应,合成了具有丰富Mo-xN/Mo-xC/W-xN/W-xC活性位点的钨钼基氮碳化物纳米电催化材料。所采用的封装作用和原位渗碳反应不仅防止了活性物质的流失,更使其均匀分布。促使来自气相沉积反应的挥发性CN-x物质更加充分的被捕获,致使封装结构中的金属氧化物被氮化,合成了钨钼基氮碳化物纳米材料在低浓度电解液中具备高效的三功能电催化性能。(The invention discloses a tungsten-molybdenum-based carbonitride nano material and a preparation method and application thereof, wherein a packaging strategy is adopted to introduce phosphotungstic acid hydrate and phosphomolybdic acid hydrate into a copper-based metal organic framework compound as active species to prepare the tungsten-molybdenum-based nano material with a nano octahedral packaging structure, and then the tungsten-molybdenum-based nano material is synthesized into a tungsten-molybdenum-based nano material with rich Mo through a vapor deposition reaction with melamine or dicyandiamide at a high temperature x N/Mo x C/W x N/W x C, tungsten molybdenum based nitrogen carbide nano electro-catalytic material of active sites. The adopted encapsulation effect and the in-situ carburization reaction not only prevent the loss of active substances, but also ensure the uniform distribution of the active substances. Promotion of volatile CN from vapor deposition reaction x The substance is more fully captured, so that the metal oxygen in the packaging structureThe compound is nitrided, and the synthesized tungsten-molybdenum-based carbonitride nano material has efficient three-function electro-catalytic performance in low-concentration electrolyte.)

1. The preparation method of the tungsten-molybdenum-based carbonitride nano material is characterized by comprising the following steps of:

(1) introducing phosphotungstic acid hydrate and phosphomolybdic acid hydrate into a copper-based metal organic framework compound to prepare a tungsten-molybdenum-based nano material with a nano octahedral structure;

(2) and (2) carrying out vapor deposition reaction on the tungsten-molybdenum-based nano material obtained in the step (1) and a nitrogen source precursor to obtain the tungsten-molybdenum-based carbonitride nano material.

2. The method for preparing the tungsten-molybdenum-based carbonitride nano material as claimed in claim 1, wherein the step (1) includes the steps of:

(a) sequentially dissolving copper acetate hydrate, L-glutamic acid, phosphomolybdic acid hydrate and phosphotungstic acid hydrate into distilled water, stirring until the solid is completely dissolved to obtain a mixed solution A, then pouring the pyromellitic acid solution into the mixed solution A, stirring, centrifuging, collecting precipitate, washing the precipitate with ethanol, and then drying in vacuum to obtain a substance B;

(b) heating the substance B obtained in the step (a) under a protective atmosphere until the temperature is raised to 600-700 ℃, preserving the heat, and cooling to room temperature to obtain a substance C;

(c) and (C) dispersing the substance C obtained in the step (b) in an iron salt aqueous solution, stirring, centrifuging, collecting the precipitate, washing the precipitate with deionized water, and finally performing vacuum drying to obtain the tungsten-molybdenum-based nano material.

3. The method for preparing the tungsten-molybdenum-based carbonitride nano material as claimed in claim 2, wherein the molar ratio of the copper acetate hydrate, the L-glutamic acid, the phosphotungstic acid hydrate and the phosphomolybdic acid hydrate in the mixed solution A in the step (a) is 3: 1 to (0.2-2) in sequence; the volume ratio of the mixed solution A to the trimesic acid solution is 1: 1; the pyromellitic acid solution is 0.02mol/L of pyromellitic acid ethanol solution.

4. The method for preparing tungsten-molybdenum-based carbonitride nano material as claimed in claim 1, wherein the step (2) includes the steps of;

placing the tungsten-molybdenum-based nano material and the nitrogen source precursor at two ends of a quartz porcelain boat, then placing the quartz porcelain boat in protective atmosphere, and heating to 700-900 ℃ at the speed of 5 ℃/min for calcination.

5. The method for preparing the tungsten-molybdenum-based carbonitride nano material as claimed in claim 4, wherein the mass ratio of the tungsten-molybdenum-based nano material to the nitrogen source precursor is 1: 5-10.

6. The method as claimed in claim 5, wherein the nitrogen source precursor comprises at least one of melamine or dicyandiamide.

7. A tungsten molybdenum based carbonitride nanomaterial made by the method of any one of claims 1 to 6.

8. The use of the tungsten molybdenum based carbonitride nanomaterial of claim 7 wherein the tungsten molybdenum based carbonitride nanomaterial is used to prepare an electrocatalytic material.

9. Use according to claim 8, wherein the electrocatalytic material comprises an electrocatalytic oxygen reduction material, an electrocatalytic oxygen evolution material, and an electrocatalytic hydrogen evolution material.

Technical Field

The invention relates to the technical field of electrocatalytic nano materials, in particular to a tungsten-molybdenum-based carbonitride nano material as well as a preparation method and application thereof.

Background

The upcoming global energy crisis has motivated extensive research into environmentally friendly, clean, and sustainable energy systems. Renewable fuel cells, rechargeable metal air cells, water decomposition cells and other clean energy conversion systems are currently considered as promising environmental protection technology devices. The cathodic Oxygen Reduction Reaction (ORR), anodic Oxygen Evolution Reaction (OER) and cathodic hydrogen generation reaction (HER) are of great research significance to the above-mentioned sustainable energy system. Highly efficient electrocatalysts play a critical role in these electrochemical reactions because they increase the energy conversion efficiency and selectivity involved. To date, Pt-based catalysts remain the most effective HER and ORR electrocatalysts in alkaline media, whereas IrO₂And RuO₂It has an optimum OER activity. Unfortunately, the scarcity and poor stability of these precious metals significantly hamper their large-scale application, and more importantly, these single precious metal electrocatalysts cannot simultaneously satisfy the dual-functional electrocatalytic activity of ORR/OER or OER/HER, or even the three-functional electrocatalytic activity of ORR/OER/HER, required in clean energy devices, in the same alkaline medium at low concentrations.

In which, the preparation of inorganic nano-materials by using MOFs as templates or precursors has attracted great interest of researchers. Due to the periodic arrangement of metal ions and organic ligands in the MOFs, the nano material obtained by converting the MOFs has a definite structure and chemical composition. In addition, because the metal ions and organic ligands composing the MOFs are various in variety, and the coordination strength and thermal stability between the components in the MOFs are also different, various types of nanomaterials can be synthesized by selecting different MOFs precursors or adjusting different reaction conditions. Researchers have found that pyrolysis of MOFs can produce a wide variety of porous carbon nanomaterials, including metal oxide/metal sulfide/metal phosphide-based porous carbon composites, and the like. In addition, functional materials with excellent performance can also be obtained by modifying the MOFs. The MOFs-based nano material has good application prospect in the fields of photo/electro-catalysis, energy storage, sensors, adsorption and the like. Therefore, the application of MOFs-based materials has become a research hotspot in the fields of chemistry and novel functional materials, and the development of cheap and efficient multifunctional electrocatalytic materials for realizing cost-effective energy conversion is urgently needed.

Disclosure of Invention

The invention aims to provide a tungsten-molybdenum-based nitrogen carbide nano material and a preparation method and application thereof, and aims to solve the problems in the prior art.

The invention introduces guest molecules phosphomolybdic acid hydrate (POM) and phosphotungstic acid hydrate (POW) as precursors into a copper-based metal organic framework compound, and prepares the compound with rich Mo by matching with a vapor deposition reaction strategy of melamine or dicyandiamide under the high-temperature condition_xN/Mo_xC/W_xN/W_xC active site and porous tungsten molybdenum based nitrogen carbide (MoWN/MoWC @ N-C) nano octahedral electrocatalytic material with high catalytic activity. The whole carbonization and nitridation processes are limited in a nitrogen-carbon substrate derived from MOFs, the agglomeration and the loss of tungsten-molybdenum-based nitrogen carbide active species are effectively prevented, and the three-functional electrocatalytic activity of ORR/OER/HER can be more fully exerted in low-concentration electrolyte, particularly 0.1mol/L KOH solution.

In order to achieve the purpose, the invention provides the following scheme: the invention provides a preparation method of a tungsten-molybdenum-based carbonitride nano material, which comprises the following steps:

(1) introducing phosphotungstic acid hydrate and/or phosphomolybdic acid hydrate into a copper-based metal organic framework compound to prepare a nano octahedral tungsten-molybdenum-based nano material with a packaging structure;

(2) and (2) carrying out vapor deposition reaction on the tungsten-molybdenum-based nano material obtained in the step (1) and a nitrogen source precursor to obtain a tungsten-molybdenum-based carbonitride (MoWN/MoWC @ N-C) nano material.

As a further optimization of the present invention, step (1) comprises the steps of:

(a) sequentially dissolving copper acetate hydrate, L-glutamic acid, phosphomolybdic acid hydrate and phosphotungstic acid hydrate into distilled water, stirring until the solid is completely dissolved to obtain a mixed solution A, then pouring a pyromellitic acid solution into the mixed solution A, continuously stirring for 12 hours under the conditions of normal temperature and normal pressure, centrifugally collecting precipitate, washing the precipitate for 3 times by using ethanol, and then carrying out vacuum drying at the temperature of 60 ℃ to obtain a substance B, namely a nano octahedral material POW/POM @ MOFs with a packaging structure;

(b) transferring the substance B obtained in the step (a) into a quartz porcelain boat, heating the substance B in a tubular furnace under protective atmosphere at a heating rate of 2 ℃/min step by step until the temperature is raised to 600-700 ℃, keeping the optimal temperature at 650 ℃, preserving the heat for 6h, and then naturally cooling the substance B to room temperature to obtain a substance C; in the whole roasting process, metal Mo or metal W in the substance C is always wrapped in a frame formed by a copper-based metal organic framework compound and is gradually converted into an oxide, a ligand part is converted into corresponding solid carbon, and a Cu simple substance formed in the obtained substance C needs to be removed;

(c) dispersing the substance C obtained in step (b) in 0.1M FeCl₃And (3) in the aqueous solution, continuously stirring for 6 hours to ensure that Cu elementary substance nanoparticles in the substance C are completely removed, centrifuging to collect precipitates, washing the precipitates with deionized water, and finally performing vacuum drying at the temperature of 80 ℃ to obtain the tungsten-molybdenum-based nano material.

As a further optimization of the invention, the molar ratio of the copper acetate hydrate, the L-glutamic acid, the phosphotungstic acid hydrate and the phosphomolybdic acid hydrate in the mixed solution A in the step (a) is 3: 1: 0.2-2 in sequence; the volume ratio of the mixed solution A to the trimesic acid solution is 1: 1; the pyromellitic acid solution is 0.02mol/L of pyromellitic acid ethanol solution.

As a further optimization of the present invention, step (2) comprises the following steps;

the tungsten-molybdenum-based nano material and the nitrogen source precursor are placed at two ends of a quartz porcelain boat, then placed in a protective atmosphere, heated to 700-900 ℃ at a speed of 5 ℃/min and calcined for 3-5 hours, and optimally calcined for 3 hours at 800 ℃.

As a further optimization of the present invention, the protective atmosphere is argon or nitrogen.

As a further optimization of the invention, the mass ratio of the tungsten-molybdenum-based nano material to the nitrogen source precursor is 1: 5-10, and the optimal mass ratio is 1: 5.

As a further optimization of the present invention, the nitrogen source precursor comprises at least one of melamine or dicyandiamide. Volatile CN from pyrolysis of melamine or dicyandiamide as the calcination temperature is gradually increased_xMatter is by tungsten molybdenum base nano-material (MoO)_x/WO_x@ N-C) resulting in nitridation of the metal oxide and solid carbon to form the corresponding MoWN/MoWC @ N-C nanooctahedral material.

The invention provides a tungsten-molybdenum-based carbonitride nano material prepared by the preparation method of the tungsten-molybdenum-based carbonitride nano material.

The invention also provides application of the tungsten-molybdenum-based carbonitride nano material as an electrocatalytic material.

As a further optimization of the invention, the electrocatalytic materials include electrocatalytic oxygen reduction (ORR) materials, electrocatalytic Oxygen Evolution (OER) materials, and electrocatalytic Hydrogen Evolution (HER) materials.

The MoWN/MoWC @ N-C electro-catalytic material is tested in 0.1mol/L KOH alkaline solution for electro-catalytic oxygen reduction, electro-catalytic oxygen evolution and hydrogen evolution performances, excellent three-function electro-catalytic activity and stability are shown, and the three-function electro-catalytic performance of the prepared MoWN/MoWC @ N-C material is greatly influenced by the synergistic effect of a multi-component heterostructure formed by different molar ratios of Mo and W and the carbonization temperature.

The invention discloses the following technical effects:

(1) the invention adopts a simple MOFs packaging auxiliary synthesis strategy, and introduces guest molecules phosphomolybdate hydrate or phosphotungstic acid hydrate as a common precursor into Cu-based MOFs (copper-based metal organic frameworks) with a main structureSkeleton compound), the Mo with rich content is prepared by matching with a vapor deposition strategy_xN/Mo_xC/W_xN/W_xC active site and porous MoWN/MoWC @ N-C nano octahedral electrocatalytic material with high catalytic activity. Solves the technical problem that the tungsten-molybdenum-based electrocatalytic active species are difficult to obtain from single MOFs materials, and provides a simpler and more convenient synthesis method. Meanwhile, the non-coordinated POM and POW are also uniformly distributed in a closed space and are surrounded by the organic ligand, so that a uniform carburization reaction process is ensured to generate corresponding electrocatalytic active sites. The whole carbonization and nitridation processes are limited in the nitrogen-carbon matrix derived from MOFs, so that the agglomeration and the loss of tungsten-molybdenum-based nitrogen carbide active species are effectively prevented, and the ORR/OER/HER three-function electrocatalytic activity of the tungsten-molybdenum-based nitrogen carbide can be more fully exerted.

(2) The ORR/HER/OER performance of the prepared electro-catalytic material is greatly influenced by the synergistic effect of the multi-component heterostructure in the MoWN/MoWC @ N-C material and the carbonization temperature. The ordered mesoporous structure can construct an ideal three-phase interface for an electrocatalysis process, provides sufficient electrocatalysis active sites and electron transmission channels for reactants and intermediates, thereby accelerating the kinetics of three-function electrocatalysis reaction, and has a synergistic effect between metal and carbon matrix components, thereby realizing higher electrocatalysis performance.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a scanning electron micrograph of MoWN/MoWC @ N-C-800 prepared in example 1;

FIG. 2 shows MoWN/MoWC @ N-C-800, Mo prepared in example 1 and examples 7-8₂N/[email protected]、W₂A comparison graph of electrocatalytic oxygen reduction performance of N/WC @ N-C-800;

FIG. 3 is a graph comparing the electrocatalytic oxygen reduction stability of MoWN/MoWC @ N-C-800 prepared in example 1 with commercial Pt/C;

FIG. 4 shows MoWN/MoWC @ N-C-800, Mo prepared in example 1 and examples 7-8₂N/[email protected]、W₂A comparison graph of electrocatalytic hydrogen evolution performance of N/WC @ N-C-800;

FIG. 5 shows MoWN/MoWC @ N-C-800, Mo prepared in example 1 and examples 7-8₂N/[email protected]、W₂A comparison graph of electrocatalytic oxygen evolution performance of N/WC @ N-C-800;

FIG. 6 is a comparative XRD plot of MoWN/MoWC @ N-C-800, MoWN/MoWC @ N-C-700, and MoWN/MoWC @ N-C-900 prepared in examples 1-3;

FIG. 7 is a Raman comparison of MoWN/MoWC @ N-C-800, MoWN/MoWC @ N-C-700, and MoWN/MoWC @ N-C-900 prepared in examples 1-3;

FIG. 8 is a graph comparing the impedances of MoWN/MoWC @ N-C-800, MoWN/MoWC @ N-C-700, and MoWN/MoWC @ N-C-900 prepared in examples 1-3.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Example 1

(1) Weighing 3mmol of copper acetate monohydrate, 1mmol of L-glutamic acid, 0.24mmol of phosphomolybdic acid hydrate and 0.26mmol of phosphotungstic acid hydrate, sequentially dissolving the copper acetate monohydrate, the L-glutamic acid, the phosphomolybdic acid hydrate and the phosphotungstic acid hydrate into 100ml of distilled water, stirring until the solid is completely dissolved to obtain a mixed solution A, pouring 100ml of an ethanol solution of pyromellitic acid with the molar concentration of 0.02mol/L into the mixed solution A under the conditions of room temperature and continuous stirring, continuously stirring for 12 hours at the speed of 500 revolutions per minute under the conditions of normal temperature and normal pressure, centrifugally collecting a synthesized green precipitate, continuously washing for 3 times by using ethanol, and finally drying in vacuum for 24 hours at the temperature of 60 ℃ to obtain a substance B.

(2) Transferring the substance B obtained in the step (1) into a quartz porcelain boat, then heating the substance B in a tubular furnace under Ar atmosphere at the heating rate of 2 ℃/min step by step until the temperature rises to 650 ℃, keeping the temperature for 6h, and then naturally cooling the substance B to room temperature to obtain the nano octahedral electrocatalytic material Cu-MoO_x/WO_x@N-C。

(3) Subjecting the Cu-MoO obtained in the step (2)_x/WO_x@ N-C dispersed in sufficient 0.1M FeCl₃Stirring for 6 hr to remove Cu nanoparticles completely, centrifuging to collect precipitate, washing with deionized water for several times, and vacuum drying at 80 deg.C to obtain octahedron nanoparticlesCatalytic material MoO_x/WO_x@N-C。

(4) Weighing 0.4g of the black porous MoO obtained in step (3)_x/WO_xThe @ N-C nano octahedron and 2g of dicyandiamide are placed at two ends of a quartz porcelain boat, then the quartz porcelain boat is placed in a tubular furnace under Ar atmosphere, and is calcined for 3 hours at 800 ℃ at the heating rate of 5 ℃/min, so that metal oxide and solid carbon are nitrided, and the obtained tungsten molybdenum based nitride carbide nano octahedron electro-catalytic material is marked as MoWN/MoWC @ N-C-800.

An SEM image of MoWN/MoWC @ N-C-800 prepared in example 1 is shown in FIG. 1; it can be seen from the figure that the tungsten molybdenum based carbonitride nanomaterial prepared in example 1 is octahedral structure with an encapsulation structure.

The electrocatalytic oxygen reduction stability of MoWN/MoWC @ N-C-800 prepared for example 1 was compared to commercial Pt/C, see FIG. 3; from FIG. 3, it can be concluded that MoWN/MoWC @ N-C-800 has superior long term stability compared to commercial Pt/C.

Example 2

The preparation method is the same as that of example 1, except that the temperature in the step (4) is 700 ℃, and the obtained tungsten molybdenum nitride based nano octahedral electrocatalytic material is marked as MoWN/MoWC @ N-C-700.

Example 3

The preparation method is the same as that of example 1, except that the temperature in the step (4) is 900 ℃, and the obtained tungsten molybdenum nitride based nano octahedral electrocatalytic material is marked as MoWN/MoWC @ N-C-900.

A comparison of XRD of the tungsten molybdenum based nitride nanooctahedral electrocatalytic materials prepared in examples 1-3 is shown in fig. 6; as can be seen from FIG. 6, by comparing the standard cards, it was found that the diffraction peaks appeared corresponding to the crystalline phases of different metal nitrocarbides, Mo respectively₂N(JCPDS No.25-1368)、MoC(JCPDS No.45-1015)、W₂N (JCPDS No.25-1257) and WC (JCPDS No.73-0471), indicating that the unique Mo is successfully synthesized by adopting the unique MOFs encapsulation strategy and matching with the vapor deposition strategy₂N/MoC/W₂A porous nano octahedral electrocatalytic material with an N/WC heterostructure.

Tungsten molybdenum based nitride nanooctahedral prepared in examples 1-3Raman comparison of bulk electrocatalytic materials, see fig. 7; as can be seen from FIG. 7, the MoWN/MoWC @ N-C-800 electrocatalytic materials showed relatively high I values in MoWN/MoWC @ N-C-700 and MoWN/MoWC @ N-C-900_D/I_GThe value (1.28) shows that the addition of the molybdenum-tungsten bimetallic active component can promote the formation of more carbon structural defects in the prepared sample and is more beneficial to the improvement of the electrocatalytic performance.

Impedance comparison of tungsten molybdenum based nitride nanooctahedral electrocatalytic materials prepared in examples 1-3, see FIG. 8; as can be derived from FIG. 8, the half-circle radius (Rct) of the MoWN/MoWC @ N-C-800(58.97 Ω) electrocatalytic material was smaller than that of MoWN/MoWC @ N-C-700(91.57 Ω) and MoWN/MoWC @ N-C-900(72.71 Ω), indicating that

MoWN/MoWC @ N-C-800 has a smaller charge transfer resistance and good conductivity, showing easier electrochemical kinetics to enhance OER/ORR/HER electrocatalytic activity.

Example 4

(1) Weighing 3mmol of copper acetate monohydrate, 1mmol of L-glutamic acid, 0.2mmol of phosphomolybdic acid hydrate and 1.2mmol of phosphotungstic acid hydrate, sequentially dissolving the copper acetate monohydrate, the L-glutamic acid, the phosphomolybdic acid hydrate and the phosphotungstic acid hydrate into 100ml of distilled water, stirring until the solid is completely dissolved to obtain a mixed solution A, pouring 100ml of an ethanol solution of pyromellitic acid with the molar concentration of 0.02mol/L into the mixed solution A under the conditions of room temperature and continuous stirring, continuously stirring for 12 hours at the speed of 500 revolutions per minute under the conditions of normal temperature and normal pressure, centrifugally collecting a synthesized green precipitate, continuously washing for 3 times by using ethanol, and finally drying in vacuum for 24 hours at the temperature of 60 ℃ to obtain a substance B.

(2) Transferring the substance B obtained in the step (1) into a quartz porcelain boat, then heating the substance B in a tubular furnace under Ar atmosphere at the heating rate of 2 ℃/min step by step until the temperature rises to 600 ℃, keeping the temperature for 6h, and then naturally cooling the substance B to the room temperature to obtain the nano octahedral electrocatalytic material Cu-MoO_x/WO_x@N-C。

(3) Subjecting the Cu-MoO obtained in the step (2)_x/WO_x@ N-C dispersed in sufficient 0.1M FeCl₃In aqueous solution and stirring was continued for 6 hours to ensure complete removal of elemental Cu nanoparticles, and the treated samples were collected by centrifugation and separated by deionizationWashing with water for several times, centrifuging, collecting precipitate, washing with deionized water for several times, and vacuum drying at 80 deg.C to obtain nanometer octahedral electrocatalytic material MoO_x/WO_x@N-C。

(4) Weighing 0.2g of the black porous MoO obtained in step (3)_x/WO_xThe @ N-C nano octahedron and 2g of melamine are placed at two ends of a quartz porcelain boat, and then the quartz porcelain boat is placed in a tubular furnace under Ar atmosphere to be calcined for 5 hours at 800 ℃ at the heating rate of 5 ℃/min, so that metal oxide and solid carbon are nitrided, and the tungsten molybdenum based nitride carbide nano octahedron electrocatalytic material MoWN/MoWC @ N-C is obtained.

Example 5

(1) Weighing 3mmol of copper acetate monohydrate, 1mmol of L-glutamic acid, 1.0mmol of phosphomolybdic acid hydrate and 2mmol of phosphotungstic acid hydrate, sequentially dissolving the copper acetate monohydrate, the L-glutamic acid, the phosphomolybdic acid hydrate and the phosphotungstic acid hydrate into 100ml of distilled water, stirring the solution until the solid is completely dissolved to obtain a mixed solution A, pouring 100ml of an ethanol solution of pyromellitic acid with the molar concentration of 0.02mol/L into the mixed solution A under the conditions of room temperature and continuous stirring, continuously stirring the solution for 12 hours at the stirring speed of 500 revolutions per minute under the conditions of normal temperature and normal pressure, centrifugally collecting a synthesized green precipitate, continuously washing the precipitate with ethanol for 3 times, and finally drying the precipitate for 24 hours under vacuum at the temperature of 60.

(2) Transferring the substance B obtained in the step (1) into a quartz porcelain boat, then heating the substance B in a tubular furnace in the nitrogen atmosphere at the heating rate of 2 ℃/min step by step until the temperature rises to 700 ℃, keeping the temperature for 6h, and then naturally cooling the substance B to the room temperature to obtain the nano octahedral electrocatalytic material Cu-MoO_x/WO_x@N-C。

(3) Subjecting the Cu-MoO obtained in the step (2)_x/WO_x@ N-C dispersed in sufficient 0.1M FeCl₃Stirring for 6 hours continuously in the water solution to ensure that Cu elementary substance nano particles are thoroughly removed, centrifuging, collecting precipitate, washing for multiple times by deionized water, and finally drying in vacuum at 80 ℃ to obtain the nano octahedral electrocatalytic material MoO_x/WO_x@N-C。

(4) Weighing 0.25g of the black porous MoO obtained in step (3)_x/WO_x@ N-C nanooctahedra and 2g dicyandiamidePlacing the quartz ceramic boat at two ends of the quartz ceramic boat, then placing the quartz ceramic boat in a tubular furnace under Ar atmosphere, and calcining the quartz ceramic boat for 4 hours at 900 ℃ at the heating rate of 5 ℃/min, so that the metal oxide and the solid carbon are nitrided, and the tungsten molybdenum nitride carbide nano octahedral electrocatalytic material MoWN/MoWC @ N-C is obtained.

Example 6

The technical scheme is the same as that of example 5, except that 2mmol of phosphomolybdic acid hydrate and 1.3mmol of phosphotungstic acid hydrate are added in the step (1).

Example 7

(1) Weighing 3mmol of copper acetate monohydrate, 1mmol of L-glutamic acid and 0.24mmol of phosphomolybdic acid hydrate, sequentially dissolving the copper acetate monohydrate, the L-glutamic acid and the phosphomolybdic acid hydrate into 100ml of distilled water, stirring the mixture until the solid is completely dissolved to obtain a mixed solution A, pouring 100ml of an ethanol solution of pyromellitic acid with the molar concentration of 0.02mol/L into the mixed solution A under the conditions of room temperature and continuous stirring, continuously stirring the mixture for 12 hours at the speed of 500 revolutions per minute under the condition of normal temperature and normal pressure, centrifugally collecting the synthesized green precipitate, continuously washing the precipitate for 3 times by using ethanol, and finally drying the precipitate for 24 hours under vacuum at the temperature of 60 ℃ to obtain a substance B.

(2) Transferring the substance B obtained in the step (1) into a quartz porcelain boat, then heating the substance B in a tubular furnace under Ar atmosphere at the heating rate of 2 ℃/min step by step until the temperature rises to 650 ℃, keeping the temperature for 6h, and then naturally cooling the substance B to room temperature to obtain the nano octahedral electrocatalytic material Cu-MoO_x@N-C-650。

(3) Subjecting the Cu-MoO obtained in the step (2)_x@ N-C-650 dispersed in sufficient 0.1M FeCl₃Stirring for 6 hours continuously in the water solution to ensure that Cu simple substance nano particles are thoroughly removed, centrifuging, collecting precipitate, washing for multiple times by deionized water, and finally drying in vacuum at 80 ℃ to obtain the nano octahedron electro-catalysis material marked as MoO_x@N-C-650。

(4) Weighing 0.4g of the black porous MoO obtained in step (3)_xThe @ N-C nano octahedron and 2g dicyandiamide are placed at two ends of quartz porcelain boat, then they are placed in tubular furnace under Ar atmosphere and calcined at 800 deg.C for 3 hr at heating rate of 5 deg.C/min so as to make metal oxide and solid carbon be nitrided, and the obtained nano octa octahedronThe surface body electrocatalytic material is marked as Mo₂N/[email protected]。

Example 8

(1) Weighing 3mmol of copper acetate monohydrate, 1mmol of L-glutamic acid and 0.26mmol of phosphotungstic acid hydrate, sequentially dissolving the copper acetate monohydrate, the L-glutamic acid and the phosphotungstic acid hydrate into 100ml of distilled water, stirring until the solid is completely dissolved to obtain a mixed solution A, pouring 100ml of an ethanol solution of pyromellitic acid with the molar concentration of 0.02mol/L into the mixed solution A under the conditions of room temperature and continuous stirring, continuously stirring for 12 hours at the speed of 500 revolutions per minute under the condition of normal temperature and normal pressure, centrifugally collecting a synthesized green precipitate, continuously washing for 3 times by using ethanol, and finally drying for 24 hours in vacuum at the temperature of 60 ℃ to obtain a substance B.

(2) Transferring the substance B obtained in the step (1) into a quartz porcelain boat, then heating the substance B in a tubular furnace in Ar atmosphere at the heating rate of 2 ℃/min step by step until the temperature rises to 650 ℃, keeping the temperature for 6h, and then naturally cooling the substance B to room temperature to obtain the nano octahedral electrocatalytic material Cu-WO_x@N-C-650。

(3) Subjecting the Cu-WO obtained in step (2)_x@ N-C-650 dispersed in sufficient 0.1M FeCl₃Stirring for 6 hours continuously in the water solution to ensure that Cu simple substance nano particles are thoroughly removed, centrifuging, collecting precipitate, washing for multiple times by deionized water, and finally drying in vacuum at 80 ℃ to obtain the nano octahedral electrocatalytic material WO_x@N-C-650。

(4) Weighing 0.4g of the black porous WO obtained in step (3)_xThe @ N-C nano octahedron and 2g dicyandiamide are placed at two ends of quartz porcelain boat, then they are placed in tubular furnace under Ar atmosphere and calcined at 800 deg.C for 3 hr at the rate of 5 deg.C/min so as to make metal oxide and solid carbon be nitrided, and the obtained nano octahedron electrocatalytic material is marked as W₂N/[email protected]。

MoWN/MoWC @ N-C-800, Mo prepared in example 1 and examples 7-8₂N/[email protected]、W₂Comparison of the electrocatalytic oxygen reduction performance of N/WC @ N-C-800 is shown in FIG. 2. As can be derived from FIG. 2, MoWN/MoWC @ N-C-800 compared to Mo in the electrocatalytic oxygen reduction test₂N/[email protected]、W₂Comparative samples of N/WC @ N-C-800, etc. haveThe larger initial potential, half-wave potential and limiting current density show the optimal electrocatalytic oxygen reduction performance.

MoWN/MoWC @ N-C-800, Mo prepared in example 1 and examples 7-8₂N/[email protected]、W₂Comparing the electrocatalytic hydrogen evolution performance of N/WC @ N-C-800; see fig. 4. As can be derived from FIG. 4, MoWN/MoWC @ N-C-800 compared to Mo was tested in the electrocatalytic hydrogen evolution test₂N/[email protected]、W₂Comparative samples such as N/WC @ N-C-800 and the like have the current density of-10 mA/cm²The minimum potential available at this time, of-0.17V (relative to RHE), represents the optimum electrocatalytic hydrogen evolution performance.

MoWN/MoWC @ N-C-800, Mo prepared in example 1 and examples 7-8₂N/[email protected]、W₂Comparing the electrocatalytic oxygen evolution performance of N/WC @ N-C-800; see fig. 5. As can be derived from FIG. 5, MoWN/MoWC @ N-C-800 compared to Mo was tested in the electrocatalytic oxygen evolution test₂N/[email protected]、W₂N/WC @ N-C-800 and other comparative samples at 10mA/cm²Has a minimum operating voltage of 1.61V (relative to RHE) at a current density of (a), and exhibits an optimum electrocatalytic oxygen evolution performance.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.