CN109449439B

CN109449439B - Preparation method and application of cobalt-molybdenum-sulfur/graphene composite material

Info

Publication number: CN109449439B
Application number: CN201811336005.6A
Authority: CN
Inventors: 杨春成; 陈丽新; 张莹; 文子; 赵明; 蒋青
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2018-11-12
Filing date: 2018-11-12
Publication date: 2022-05-24
Anticipated expiration: 2038-11-12
Also published as: CN109449439A

Abstract

The invention relates to a preparation method and application of a cobalt-molybdenum-sulfur/graphene composite material. The composite material is prepared according to the following steps: a. preparing graphite oxide according to a modified Hummers method; b. synthesizing a cobalt molybdenum sulfide (CoMoS) precursor by a chemical precipitation method; c. GO in CoMoS precursor solution with hydrazine hydrate (N) under oil bath conditions₂H₄·H₂O) reduction, then in N₂Annealing treatment under the atmosphere; d. and soaking the obtained product in hydrochloric acid, and then cleaning the product by using deionized water and ethanol to prepare the CoMoS/RGO composite material. The composite material is used as a catalyst for Hydrogen Evolution Reaction (HER), shows excellent catalytic performance, has an initial potential of only 28mV, and has a current density of 10mA cm^‑2The potential was only 100 mV. CoMoS and bulk MoS prepared under the same conditions and under the same current density₂Compared with the CoMoS/RGO composite material, the CoMoS/RGO composite material has obvious advantages. The invention can also be expanded to the design of other catalyst systems, and provides a new idea for further developing high-efficiency and low-cost catalysts.

Description

Preparation method and application of cobalt-molybdenum-sulfur/graphene composite material

The technical field is as follows:

the invention relates to a preparation method of a cobalt-molybdenum-sulfur/graphene composite material and application of the cobalt-molybdenum-sulfur/graphene composite material as a catalyst in hydrogen evolution reaction.

Background art:

energy crisis and environmental pollution have forced the search for a renewable clean energy source to reduce fossil fuel consumption. Hydrogen is widely considered as one of the most promising energy carriers due to its advantages of higher energy density and environmental friendliness. Electrochemical water splitting is an economical and efficient method for producing hydrogen. Accordingly, the corresponding device requires an efficient and stable catalyst to promote the Hydrogen Evolution Reaction (HER). Platinum (Pt) is currently the most effective HER catalyst, but its use is severely limited by scarce resources and high cost. In recent years, most studies on HER have focused on finding a resource-rich material that can replace Pt as a catalyst.

Due to its unique structural characteristics and appropriate hydrogen absorption free energy, molybdenum disulfide is regarded as an efficient HER catalyst with potential to replace Pt, and has received extensive attention. However, the catalytic performance of molybdenum disulfide is still not comparable to that of Pt, mainly because: (1) the active sites of the molybdenum disulfide are few, the molybdenum disulfide is concentrated on the edge, and the surface is inert; (2) molybdenum disulfide itself is relatively poor in conductivity. In order to improve the catalytic performance of the molybdenum disulfide, scientific research personnel at home and abroad carry out a great deal of research and obtain certain achievements. According to literature reports, the active position of molybdenum disulfide can be increased by regulating and controlling the size and the shape, doping noble metal, manufacturing sulfur vacancy and other methods, and the catalytic performance of the molybdenum disulfide is improved; molybdenum disulfide and materials with good conductivity, such as graphene, three-dimensional porous metal, nitrogen-doped carbon nanofiber and the like, are compounded to improve the conductivity of the molybdenum disulfide, accelerate the electrochemical reaction rate and improve the catalytic performance of the molybdenum disulfide. The above method is very effective for improving the catalytic performance of molybdenum disulfide, but the development of the catalyst is restricted by the higher cost and the complicated preparation process. The molybdenum disulfide and cobalt are alloyed, so that the surface of the molybdenum disulfide can be activated, the molybdenum disulfide has more active sites, and meanwhile, impurity energy levels are introduced, and therefore the conductivity of the catalyst is increased. In addition, the graphene has a large specific surface area and good conductivity, and the cobalt-molybdenum-sulfur is compounded with the graphene, so that the conductivity of the catalyst is improved, the agglomeration of cobalt-molybdenum-sulfur nano particles can be inhibited, the active sites of the nano particles are increased, and the catalytic performance of the catalyst is effectively improved.

The invention content is as follows:

the invention aims to provide a preparation method and application of a cobalt-molybdenum-sulfur/graphene composite material combining a chemical precipitation method and heat treatment. In the composite material, the introduction of cobalt can activate the inert surface of molybdenum disulfide, so that the active sites of the molybdenum disulfide are increased, the catalytic performance of the molybdenum disulfide is improved, and meanwhile, the introduction of impurity energy level can also improve the conductivity of the catalyst; the graphene has a large specific surface area and good conductivity, can effectively reduce charge transfer resistance in an electrochemical reaction process, can inhibit the agglomeration of cobalt molybdenum sulfur nanoparticles, increases the active sites of the cobalt molybdenum sulfur nanoparticles, and is beneficial to improving the catalytic performance. The composite material is used as a catalyst for hydrogen evolution reaction, shows excellent catalytic performance and has a certain application prospect. The invention can also be expanded to the design of other catalyst systems, and provides a new idea for further developing high-efficiency and low-cost catalysts.

The above purpose of the invention is realized by the following technical scheme:

a preparation method of a cobalt molybdenum sulfur/graphene composite material comprises the following steps:

a. synthesizing graphite oxide according to a modified Hummers method;

b. synthesizing a CoMoS precursor by a chemical precipitation method, wherein the chemical precipitation method comprises the step of adding 0.262-0.272 g (NH)₄)₂MoS₄And 0.232 to 0.242g of CoCl₂·6H₂O is respectively dissolved in 20ml of deionized water, placed on a magnetic stirrer for stirring, and then CoCl is added₂The solution is added dropwise to (NH)₄)₂MoS₄Generating black precipitate in the solution, and continuously stirring the solution on a magnetic stirrer for 30 min;

c. adding 0.44-0.52 ml of graphite oxide into the solution containing the CoMoS precursor, performing ultrasonic treatment for 15min, then placing the solution in an oil bath, and performing ultrasonic treatment at the temperature of 95 ℃ by using N₂H₄·H₂Reducing the O for 0.5-1.5 h, washing the obtained black powder with water and ethanol, and drying in a vacuum drying oven;

d. the prepared black powder was placed in a tube furnace in N₂And (3) preserving the heat for 4-6 hours at 450-550 ℃ in the atmosphere, soaking the obtained product in HCl, then respectively washing the product with water and ethanol, and drying the product to obtain the CoMoS/RGO composite material.

The above-mentionedWhen the CoMoS/RGO composite material is prepared in the step b and a CoMoS precursor is prepared, CoCl is required₂The solution is added dropwise to (NH)₄)₂MoS₄In the solution, the precipitate is prevented from aggregating and is not uniform in size.

When the CoMoS/RGO composite material is prepared in the step c, after the graphite oxide is added into the solution containing the CoMoS precursor, ultrasonic treatment needs to be carried out on the mixed solution, so that the two substances can be uniformly mixed and fully contacted.

In the step d, the mixture of the CoMoS precursor and the RGO is placed in N₂And annealing in the atmosphere, wherein the aim is to decompose the CoMoS precursor to generate CoMoS and enhance the interaction among the components in the composite material.

The cobalt molybdenum sulfur/graphene composite material is used as a catalyst for electrochemical test, and comprises the following steps:

a. firstly, dispersing 2-4 mg of composite material (CoMoS/RGO) in 0.4-0.6 ml of water/isopropanol/naphthol solution, and then carrying out ultrasonic treatment for 20-40 min to obtain a catalyst ink solution. Taking out 15-25 mul of catalyst solution to drop on a glassy carbon electrode, and drying at room temperature to form a uniform catalyst film;

b. the electrochemical test is carried out in a standard three-electrode test system, wherein the electrode prepared in the step a is used as a working electrode, a carbon rod electrode is used as a counter electrode, a calomel electrode is used as a reference electrode, and H with the concentration of 0.4-0.6M is used as₂SO₄The solution is used as electrolyte;

c. the CoMoS/RGO composite material is used as a working electrode to be tested on an Ivium-n-Stat electrochemical workstation, a polarization curve test is carried out on a rotating disk electrode with the rotating speed of 2025rpm, the potential scanning range relative to a reversible hydrogen electrode is 0 to-0.4V, and the scanning speed is 5mV s^-1(ii) a The electrochemical impedance spectrum is under the constant voltage of-0.15V relative to the potential of the reversible hydrogen electrode, and the frequency is 100K Hz-0.1 Hz; the current-time curve test is that under a constant voltage of-0.08V relative to the potential of the reversible hydrogen electrode, the scanning time is 20000 s;

d. the prepared CoMoS/RGO composite material is used as a catalyst for hydrogen evolution reaction,shows excellent catalytic performance, the initial potential is only 28mV, and the current density is 10mA cm^-2At the same current density, the potential is only 100mV, with the CoMoS and bulk MoS produced under the same conditions₂Compared with the prior art, the method has obvious advantages.

The invention has the technical effects that:

the invention synthesizes an efficient catalyst by a simple method, and MoS is synthesized₂The Co-activated carbon is alloyed with Co and then compounded with RGO to prepare the CoMoS/RGO, the composite material has good conductivity, can effectively reduce the charge transfer resistance in the electrochemical reaction process, and the introduction of Co can activate the MoS₂The surface of (2) increases the active sites thereof, and also introduces impurity levels, so that the conductivity is improved, thereby showing excellent catalytic performance.

Description of the drawings:

FIG. 1, polarization curves for different catalysts in inventive example 1.

FIG. 2, FESEM photograph of CoMoS/RGO composite prepared in inventive example 1.

FIG. 3, FESEM photograph of CoMoS prepared in inventive example 1.

FIG. 4 TEM photograph of the CoMoS/RGO composite prepared in inventive example 1.

FIG. 5, HRTEM photograph of CoMoS/RGO composite prepared in inventive example 1.

FIG. 6, XRD diffraction pattern of CoMoS/RGO composite prepared in inventive example 1.

FIG. 7 Raman spectra of CoMoS/RGO composites prepared in inventive example 1.

FIG. 8, BET plot of CoMoS/RGO composite prepared in inventive example 1.

FIG. 9 XPS spectra of CoMoS/RGO composites prepared in inventive example 1.

FIG. 10, Mo 3d region high resolution XPS spectra of CoMoS/RGO composites prepared in inventive example 1.

FIG. 11, S2 p region high resolution XPS spectra for CoMoS/RGO composites prepared in inventive example 1.

FIG. 12, C1 s region high resolution XPS spectra for CoMoS/RGO composites prepared in inventive example 1.

FIG. 13 Co 2p region high resolution XPS spectra for CoMoS/RGO composites prepared in inventive example 1.

FIG. 14 Tafel plots for different catalysts in inventive example 1.

FIG. 15, electrochemical impedance spectra of different catalysts in inventive example 1.

FIG. 16 is a graph of time-current density relationship at constant voltage for the CoMoS/RGO composite material prepared in example 1 of the present invention (the inset is a FESEM photograph of the CoMoS/RGO composite material after 20000s stability test).

FIG. 17, FESEM photograph of CoMoS/RGO composite prepared in inventive example 2.

FIG. 18, FESEM photograph of CoMoS/RGO composite prepared in example 3 of the present invention.

The specific implementation mode is as follows:

the specific contents and embodiments of the present invention will be further described with reference to examples, which are provided for illustration only and should not be construed as limitations on the technical solutions of the present invention. Examples 2 and 3 of the present invention are similar to those of example 1, and example 1 will be described in detail.

Example 1

The preparation process and steps in this example are as follows:

(1) synthesizing graphite oxide according to a modified Hummers method;

(2) synthesis of a CoMoS precursor by chemical precipitation, 0.267g (NH)₄)₂MoS₄And 0.237g CoCl₂·6H₂O is respectively dissolved in 20ml of deionized water, placed on a magnetic stirrer for stirring, and then CoCl is added₂The solution is added dropwise to (NH)₄)₂MoS₄Generating black precipitate in the solution, and continuously stirring the solution on a magnetic stirrer for 30 min;

(3) 0.48ml of graphite oxide is added into the solution containing the CoMoS precursor for ultrasonic treatment for 15min and then placedIn an oil bath at a temperature of 95 ℃ with N₂H₄·H₂Reducing O for 1h, washing the obtained black powder with water and ethanol, and then drying in a vacuum drying oven;

(4) the prepared black powder was placed in a tube furnace in N₂Preserving heat for 5 hours at 500 ℃ in the atmosphere, soaking the obtained product in hydrochloric acid, respectively washing the product with water and ethanol, and drying the product to obtain a CoMoS/RGO composite material;

(5) 3mg of the composite material (CoMoS/RGO) was dispersed in 0.5ml of a water/isopropanol/naphthol solution, followed by sonication for 30min to obtain a catalyst ink solution. 20 mul of catalyst solution is taken out and dropped on a glassy carbon electrode as a working electrode, a calomel electrode as a reference electrode, and H with the concentration of 0.5M₂SO₄The solution is used as electrolyte to form a standard three-electrode system for electrochemical test;

(6) the CoMoS/RGO composite material is used as a working electrode to be tested on an Ivium-n-Stat electrochemical workstation, a polarization curve test is carried out on a rotating disk electrode with the rotating speed of 2025rpm, the potential scanning range of the potential relative to a reversible hydrogen electrode is 0 to-0.4V, and the scanning speed is 5mV s^-1(ii) a The electrochemical impedance spectrum is under the constant voltage of-0.15V relative to the potential of the reversible hydrogen electrode, and the frequency is 100K Hz-0.1 Hz; the current-time curve test is that under a constant voltage of-0.08V relative to the potential of the reversible hydrogen electrode, the scanning time is 20000 s;

the morphology and the structure of the CoMoS/RGO composite material are characterized in that:

the surface morphology of the CoMoS/RGO composite material is characterized by a Scanning Electron Microscope (SEM). FIG. 2 is an SEM of CoMoS/RGO. It can be seen that the CoMoS nanoparticles are uniformly distributed, with a diameter of about 70 nm. The CoMoS nanoparticles (FIG. 3) prepared under the same conditions have different sizes and obvious agglomeration phenomenon. This indicates that the presence of RGO in the composite can inhibit the agglomeration of the CoMoS nanoparticles. FIG. 4 is a TEM photograph of CoMoS/RGO, which is cross-linked with each other, and has good electrical conductivity, and can reduce the internal resistance of the catalyst and accelerate the electrochemical reaction rate when used as a substrate of the composite material; meanwhile, RGO can inhibit the agglomeration of CoMoS nano particles to ensure that the CoMoS nano particles can be agglomeratedWith more active sites. FIG. 5 is an HRTEM photograph of CoMoS/RGO with a lattice spacing of 0.624nm for the (002) lattice of CoMoS. FIG. 6 is an XRD diffraction pattern of the CoMoS/RGO composite material, wherein a diffraction peak at 26.4 degrees is a diffraction peak of RGO, and other diffraction peaks are diffraction peaks of CoMoS (PDF card is 16-0439). The structure of the CoMoS/RGO composite can be further characterized by Raman spectroscopy, as shown in FIG. 7. At 377cm^-1And 402cm^-1Respectively corresponding to MoS₂E of (A)¹ _2gAnd A_1gVibration mode, and A_1gIs much higher than E¹ _2g. A perpendicular to the plane due to polarization dependence_1gVibrational modes are excited by edge terminations, thus indicating that the CoMoS/RGO has an edge-terminated structure and thus has good HER catalytic activity. In addition, the presence of RGO can also be determined by Raman spectroscopy, with two characteristic peaks at 1359cm each^-1(D band) and 1581cm^-1(G band) intensity ratio of D band to G band is I_D/I_G1.29, a number of defects in graphene are demonstrated. FIG. 8 is N of a CoMoS/RGO composite₂Adsorption/desorption isotherms and pore size distribution profiles. The specific surface area of the composite material was 69.9m, as determined by the Brunauer-Emmer-Teller (BET) model and the Barrett-Joyner-Halenda (BJH) method²(ii) in terms of/g. In addition, as can be seen from the inset, the pore size distribution in the composite material is 3-25 nm, mainly due to MoS₂Two-dimensional materials of nano-sheet and RGO are formed by disordered self-assembly. The presence of these pores provides more active sites for the catalyst, promoting H⁺Diffuse, accelerating HER processes. FIG. 9 is an XPS survey of a CoMoS/RGO composite showing that the composite contains the elements Mo, S, Co, C and O. Fig. 10, 11, 12 and 13 are high resolution XPS spectra of Mo 3d, S2 p, C1S and Co 2p, respectively. Mo 3d in FIG. 10 can be divided into 6 fitting peaks, wherein the peak at 226.5eV is MoS₂S2S characteristic peak of (a); the two characteristic peaks at 229.2eV and 232.3eV are MoS₂Mo 3d of_5/2And 3d_3/2And relatively high binding energy of Mo 3d_5/2(229.5eV) and Mo 3d_3/2(232.8eV) is because Mo⁵⁺Presence of (a); mo at 235.9eV⁶⁺The presence of characteristic peaks is due to the oxidation of a small amount of sample. FIG. 11 is a graph showing S2 p having binding energies of 162.0eV and 163.2eV_3/2And S2 p_1/2Is MoS₂S in (1)^2-And S2 p with binding energies of 162.7eV and 164.1eV_3/2And S2 p_1/2Is due to S₂ ^2-Presence of (2) indicates MoS₂The increase of edge positions is beneficial to improving HER performance. The peak intensities of C-O and C ═ O in fig. 12 are very weak, indicating that most of the oxygen-containing functional groups in RGO were successfully removed. The Co 2p spectrum in fig. 13 can be fit to 4 pairs of characteristic peaks: the first pair is 2p of CoMoS phases located at 779.2eV and 794.1eV_3/2And 2p_1/2(ii) a The second pair is Co at 780.5eV and 796.9eV ²⁺2p of_3/2And 2p_1/2(ii) a The third and fourth pairs are satellite peaks.

The catalytic performance of the CoMoS/RGO composite material is characterized under the condition of room temperature:

electrochemical experiments were performed using a standard three-electrode test system. As shown in FIG. 1, Pt/C has the best catalytic activity, with an initial potential of 0mV and a current density of 10mA cm^-2The potential is only 38 mV. Bulk MoS₂The conductive performance of the compound is poor, and the active sites are few, so that the compound shows poor HER catalytic activity. With large MoS₂In contrast, CoMoS has a lower initial potential because of the introduction of Co which causes MoS₂The inert surface is activated and thus the catalytic performance is improved. The CoMoS/RGO composite material shows more excellent catalytic performance, the initial potential is only 28mV, and the current density is 10mA cm^-2The overpotential is only 100 mV. Such excellent properties are mainly Co, RGO and MoS₂Results of synergy: (1) co introduction energy activated MoS₂The inert surface increases the active position of the catalyst, improves the catalytic performance of the catalyst, and simultaneously introduces an impurity energy level to improve the conductivity of the catalyst; (2) RGO has larger specific surface area and good conductivity, effectively reduces the charge transfer resistance in the electrochemical reaction process, can inhibit the agglomeration of CoMoS nano particles, increases the active position of the CoMoS nano particles, and is beneficial to improving the catalytic performance of the catalyst. FIG. 14 is a drawing showingCorresponding tafel curves. The Tafel slope of Pt/C was 31.0mV dec^-1Consistent with the results reported in other literature. Bulk MoS₂The Tafel slopes of CoMoS and CoMoS/RGO were 197.9mV dec, respectively^-1,145.6mV dec^-1And 60.8mV dec^-1. Besides Pt/C, the Tafel slope of the CoMoS/RGO composite material is the lowest, which shows that the reaction rate of HER changes the fastest with the change of potential, and the point can also prove that the composite material has excellent catalytic performance. FIG. 15 is an electrochemical impedance plot of a CoMoS/RGO composite, as seen by comparison, with a bulk MoS₂Compared with the CoMoS, the charge transfer resistance of the CoMoS/RGO composite material is obviously reduced, mainly because the conductivity of the composite material is obviously improved due to the introduction of Co and RGO. FIG. 16 is a time-current density relationship for a CoMoS/RGO composite at constant voltage (-0.08V). The current density decayed by 15% after the passage of the scanning time of 20000s, due to the H in the electrolyte during the electrochemical reaction⁺Is consumed or is H produced during the reaction₂The active material is left on the surface of the electrode, so that the active material cannot be fully utilized, and the electrochemical reaction is prevented. The inset in fig. 16 is a FESEM photograph of the CoMoS/RGO composite after 20000s stability test, and it can be seen that the CoMoS/RGO composite still maintains its original structure, indicating that the composite prepared by us has better cycle stability. In conclusion, the CoMoS/RGO composite material has excellent electrocatalytic performance, which is caused by the following reasons: the introduction of RGO and Co can improve the conductivity of the catalyst and effectively reduce the charge transfer resistance in the electrochemical reaction process; co can activate MoS₂The surface of (2) increases the active sites thereof, and also introduces impurity levels, so that the conductivity is improved, thereby showing excellent catalytic performance.

Example 2

(1) Synthesizing graphite oxide according to a modified Hummers method;

(2) synthesis of a CoMoS precursor by chemical precipitation, 0.267g (NH)₄)₂MoS₄And 0.237g CoCl₂·6H₂Dissolving O in 20ml deionized water respectively, and stirring on a magnetic stirrerStirring, then adding CoCl₂The solution is added dropwise to (NH)₄)₂MoS₄Generating black precipitate in the solution, and continuously stirring the solution on a magnetic stirrer for 30 min;

(3) adding 0.24ml of graphite oxide into the solution containing the CoMoS precursor, performing ultrasonic treatment for 15min, then placing the solution in an oil bath, and performing ultrasonic treatment on the solution at the temperature of 95 ℃ by using N₂H₄·H₂Reducing O for 1h, washing the obtained black powder with water and ethanol, and drying in a vacuum drying oven;

(5) 3mg of the composite material (CoMoS/RGO) was dispersed in 0.5ml of a water/isopropyl alcohol/naphthol solution, followed by sonication for 30min to obtain a catalyst ink solution. 20 mul of catalyst solution is taken out and dropped on a glassy carbon electrode as a working electrode, a calomel electrode as a reference electrode, and H with the concentration of 0.5M₂SO₄The solution is used as electrolyte to form a standard three-electrode system for electrochemical test;

an SEM photograph of the CoMoS/RGO composite material prepared in this example is shown in FIG. 17. The figure shows that the composite material prepared by the embodiment has a similar morphology with the material prepared by the embodiment 1, and has more active sites, which is beneficial to improving the catalytic performance.

Example 3

(1) Synthesizing graphite oxide according to a modified Hummers method;

(3) 1.2ml of graphite oxide was added to the above described CoMoS containing precursorSubjecting to ultrasonic treatment for 15min, placing in oil bath, and treating with N at 95 deg.C₂H₄·H₂Reducing O for 1h, washing the obtained black powder with water and ethanol, and then drying in a vacuum drying oven;

(4) the prepared black powder was placed in a tube furnace in N₂Preserving heat for 5 hours at 500 ℃ in the atmosphere, soaking the obtained product in HCl, respectively washing the product with water and ethanol, and drying the product to obtain a CoMoS/RGO composite material;

an SEM photograph of the CoMoS/RGO composite material prepared in this example is shown in FIG. 18. The figure shows that the composite material prepared by the embodiment has similar morphology with the materials prepared by the

embodiments

1 and 2, and has more active sites, which is beneficial to improving the catalytic performance. This also fully demonstrates the wide range of applicability of this experiment.

Claims

1. A preparation method of a cobalt molybdenum sulfur/graphene composite material comprises the following steps:

a. synthesizing graphite oxide according to a modified Hummers method;

b. synthesizing a CoMoS precursor by a chemical precipitation method, wherein the chemical precipitation method comprises the step of adding 0.262-0.272 g (NH)₄)₂MoS₄And 0.232 to 0.242g of CoCl₂·6H₂O is respectively dissolved in 20ml of deionized water, placed on a magnetic stirrer for stirring, and then CoCl is added₂·6H₂O solution is added dropwise to (NH)₄)₂MoS₄Generating black precipitate in the solution, and continuously stirring the solution on a magnetic stirrer for 30 min;

c. adding 0.44-0.52 ml of graphite oxide into a solution containing a CoMoS precursor, carrying out ultrasonic treatment for 15min, then placing the solution in an oil bath,at a temperature of 95 ℃ with N₂H₄·H₂Reducing O for 0.5-1.5 h, washing the obtained black powder with water and ethanol, and then drying in a vacuum drying oven;

d. the prepared black powder was placed in a tube furnace in N₂Preserving heat for 4-6 hours at the temperature of 450-550 ℃ in the atmosphere, soaking the obtained product with hydrochloric acid, respectively washing with water and ethanol, and drying to obtain a cobalt-molybdenum-sulfur/graphene CoMoS/RGO composite material;

in step b, the CoCl is required to be added₂·6H₂O solution is added dropwise to (NH)₄)₂MoS₄In solution, Co: the Mo molar ratio is 1:1, so that the precipitate is prevented from being aggregated, and the size is not uniform;

in the step c, after the graphite oxide is added into the solution containing the CoMoS precursor, ultrasonic treatment is carried out on the mixed solution, so that the two substances can be uniformly mixed and fully contacted;

in step d, the mixture of the CoMoS precursor and the RGO is placed in N₂And annealing in the atmosphere, wherein the annealing has the function of decomposing the CoMoS precursor to generate CoMoS and simultaneously enhancing the interaction among the components in the composite material.