Composite catalyst and preparation method thereof, water electrolysis hydrogen evolution catalytic electrode and water electrolysis hydrogen evolution method

Abstract

The invention relates to the technical field of electrolyzed water catalysts, and discloses a composite catalyst and a preparation method thereof, an electrolyzed water hydrogen evolution catalytic electrode and an electrolyzed water hydrogen evolution method, and the preparation method comprises the following steps: in the presence of carrier gas, roasting transition metal sulfide containing S vacancy and a non-metal source; the non-metal source is selected from at least one of a phosphorus source, a carbon source, a nitrogen source and a selenium source; wherein the non-metal source is arranged at the upstream of the transition metal sulfide containing the S vacancy along the flow direction of the carrier gas. The preparation method can effectively adjust the electronic structure of the catalyst, and the prepared catalyst has high HER activity.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyzed water catalysts, and particularly relates to a composite catalyst, a preparation method thereof, an electrolyzed water hydrogen evolution catalytic electrode, and a method for electrolyzed water hydrogen evolution. Background Art

[0002] In the past few decades, transition metal sulfides have attracted the attention of researchers due to their low hydrogen adsorption free energy and chemical stability during the electrolyzed water hydrogen evolution process. However, the low electrical conductivity, the inert basal plane of the material itself, and the small number of exposed edge active sites of transition metal sulfides limit the catalytic activity of this material in the electrocatalytic hydrogen evolution reaction (HER). Therefore, developing an effective method to activate the inert basal plane of transition metal sulfides to increase the number of catalytic active sites is of great significance for improving its HER catalytic activity. Among them, the defect engineering modification strategy has played an important role in electrochemical hydrogen evolution. Defect engineering can effectively activate the surface of the inert substrate, provide a high surface area, and expose abundant active sites, which is very beneficial to promoting the electrocatalytic field.

[0003] Through a simple impregnation method, single-atom Ru doping induces the generation of S vacancies in sulfides. The electronic interaction between the doped-induced defects and the sulfide carrier can form new electronic states to activate the active sites and further promote the HER activity (Small Methods, 2019, 3(12): 1900653). However, the high cost and scarcity of Ru limit its wide application. Based on the above research, it shows that the vacancy defect engineering can effectively regulate the electronic structure, improve the electrical conductivity, and expose the active sites, thereby comprehensively improving the catalytic performance. However, there is still a need for in-depth research on how to design and prepare a method with rich vacancy defects and establish the connection between vacancy defects and the activity of electrocatalysts to achieve high-performance HER catalytic activity. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem of insufficient catalytic activity of transition metal sulfides in the electrocatalytic hydrogen evolution reaction (HER) in the prior art, and to provide a composite catalyst, a preparation method thereof, an electrolyzed water hydrogen evolution catalytic electrode, and a method for electrolyzed water hydrogen evolution. The composite catalyst prepared by this preparation method has a lower overpotential and higher catalytic activity in HER.

[0005] To achieve the above purpose, in the first aspect of the present invention, a preparation method of a composite catalyst is provided. The preparation method includes: roasting a transition metal sulfide containing S vacancies and a non-metal source in the presence of a carrier gas; the non-metal source is selected from at least one of a phosphorus source, a carbon source, a nitrogen source, and a selenium source;

[0006] Wherein, along the flow direction of the carrier gas, the non-metal source is placed upstream of the transition metal sulfide containing S vacancies.

[0007] The second aspect of the present invention provides a composite catalyst prepared by the above preparation method.

[0008] The third aspect of the present invention provides an electrolytic water hydrogen evolution catalytic electrode, which includes a conductive substrate and a catalytic material compounded on the surface of the conductive substrate, and the catalytic material is the composite catalyst described in the second aspect.

[0009] The fourth aspect of the present invention provides a method for electrolytic water hydrogen evolution, which includes: under the conditions of electrolytic water, using the self-electrolytic water hydrogen evolution catalytic electrode described in the third aspect as the working electrode to carry out electrolytic water reaction.

[0010] Through the above technical solutions, the present invention first proposes to use S vacancies to assist in the preparation of a composite catalyst rich in sulfur vacancies of non-metal element-doped induced transition metal sulfide by high-temperature calcination of anion-cation exchange method. This preparation method can effectively adjust the electronic structure of the catalyst. The vacancy defects expose more active sites, activate the inert basal plane of sulfide, increase the number of active sites of the catalyst, and significantly improve the HER activity. At the same time, the strong electronic interaction between the vacancy defects induced by non-metal doping and the sulfide carrier can improve the electrocatalytic performance by forming new electronic states and accelerating electron transfer. The preparation method provided by the present invention is simple and easy to implement, consumes less energy and has low cost, and can effectively avoid problems such as high energy consumption and poor catalytic stability involved in traditional preparation methods. Description of the Drawings

[0011] Figure 1 For Example 1 (MoP@Sv-MoS 2 ) in the present invention, Comparative Example 1 (MoP@MoS 2 ), Preparation Example 1 (Sv-MoS 2 ) and Comparative Preparation Example 1 (MoS 2 ) EPR diagrams;

[0012] Figure 2 (a) is a comparison diagram of Tafel slope curves for Example 1 (MoP@Sv-MoS 2 ), Comparative Example 1 (MoP@MoS 2 ), Preparation Example 1 (Sv-MoS 2 ) and Comparative Preparation Example 1 (MoS 2 ) in the present invention;

[0013] Figure 2 (b) is a comparison of the active area tests of the composite materials in Example 1, Comparative Example 1, Preparation Example 1 and Comparative Preparation Example 1;

[0014] Figure 2 (c) is MoP@Sv-MoS in Example 1 2Chronostable voltage curve of the composite material;

[0015] Figure 2 (d) is the cyclic voltammetry test curve of MoP@Sv-MoS in Example 1 2 Cyclic voltammetry test curve of the composite material under a long-time cycle. Specific implementation manners

[0016] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0017] The first aspect of the present invention provides a preparation method of a composite catalyst, and the preparation method includes: calcining a transition metal sulfide containing S vacancies and a non-metal source in the presence of a carrier gas; the non-metal source is selected from at least one of a phosphorus source, a carbon source, a nitrogen source, and a selenium source;

[0018] Wherein, along the flow direction of the carrier gas, the non-metal source is placed upstream of the transition metal sulfide containing S vacancies.

[0019] The present invention first proposes to use S vacancies to assist the preparation of a composite catalyst with sulfur vacancies induced by doping non-metal elements in transition metal sulfides through high-temperature calcination of the anion-cation exchange method. By calcining the transition metal sulfide containing S vacancies and the non-metal source, the electronic structure of the composite catalyst can be effectively adjusted. The vacancy defects expose more active sites, activate the inert basal plane of the sulfide, increase the number of active sites of the catalyst, and significantly improve the HER activity. At the same time, the strong electronic interaction between the vacancy defects induced by non-metal doping and the sulfide carrier can form new electronic states and accelerate electron transfer to improve the electrocatalytic performance.

[0020] In the present invention, the vacancy defects in the composite catalyst are characterized by electron spin resonance spectroscopy (EPR). It can be seen from the EPR results that, compared with the transition metal sulfide containing S vacancies, the vacancy content in the composite catalyst prepared by the preparation method of the present invention is further increased.

[0021] In the present invention, the instrument used for electron spin resonance spectroscopy (EPR) is a Bruker band continuous wave EPR spectrometer. The specific parameters for the test are as follows: the central magnetic field is 3500.00 G; the sweep field width is 200.00 G; the sweep field time is 30.00 s; the microwave power is 19.45 mW; the modulation amplitude is 1.000 G; the conversion time is 40.00 ms. The sample to be measured is placed in a rectangular cavity resonator with a frequency of 9.852508 GHz. The reflected microwave enters the detector through the circulator, and the resonance information can be calculated based on the absorption amount of the microwave radiation.

[0022] According to some preferred embodiments of the present invention, the mass ratio of the non-metal source to the transition metal sulfide containing S vacancies is 3-20:1, for example, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1 and other typical but non-limiting mass ratios or the range between the two. Preferably, the mass ratio of the non-metal source to the transition metal sulfide containing S vacancies is 5-10:1, and more preferably 6-9:1. Controlling the mass ratio of the non-metal source to the transition metal sulfide containing S vacancies within the above preferred range is beneficial to having appropriate vacancy defects in the prepared composite catalyst, and at the same time is beneficial to strengthening the strong electronic interaction between the vacancy defects induced by non-metal doping and the sulfide carrier, thereby improving the electrocatalytic performance of the catalyst.

[0023] The present invention has a wide selection range for the transition metal in the transition metal sulfide containing S vacancies, and any known transition metal sulfide that can be used in the electrocatalytic hydrogen evolution reaction (HER) in the art can be applied to the present invention.

[0024] According to some preferred embodiments of the present invention, the transition metal in the transition metal sulfide containing S vacancies is selected from at least one of the metal elements in Group VIB, Group VIIB, Group VIII and Group IB, preferably at least one of Fe, Co, Ni, Mo, W, Mn and Cu, preferably Mo and / or W, and more preferably Mo.

[0025] The present invention has a wide selection range for the specific substance of the non-metal source, as long as it can provide the corresponding non-metal element. Preferably, the phosphorus source is selected from at least one of phosphoric acid, sodium hypophosphite, disodium hydrogen phosphate and diammonium phosphate.

[0026] Preferably, the nitrogen source is selected from at least one of ethylenediamine, triethylamine and N,N-dimethylethylamine.

[0027] Preferably, the carbon source is selected from at least one of glucose, sodium acetate, dicyandiamide, and polyvinylidene fluoride.

[0028] Preferably, the selenium source is selected from at least one of selenium powder, sodium selenite, ammonium selenate, and tin diselenide.

[0029] According to the present invention, the roasting is carried out in the presence of a carrier gas. Along the flow direction of the carrier gas, the non-metal source is placed upstream of the transition metal sulfide containing S vacancies. It can be understood that during the roasting process, the volatile non-metal source undergoes cation-anion exchange under the flow action of the carrier gas during the gas-phase deposition process to prepare a composite catalyst in which the transition metal sulfide is rich in sulfur vacancies induced by non-metal element doping.

[0030] The present invention has a relatively wide selection range for the carrier gas, and reducing gases or inert gases that do not participate in the reaction can be applied to the present invention. Preferably, the carrier gas is selected from at least one of nitrogen, argon, and hydrogen, and can also be a mixture of any two of nitrogen, argon, and hydrogen. For example, H 2 / N 2 、H 2 / Ar, etc., and the volume ratio of any two atmospheres is 1:10 - 10:1.

[0031] According to some preferred embodiments of the present invention, relative to 1 g of the non-metal source, the flow rate of the carrier gas is 0.1 - 1.5 mL / min, preferably 0.3 - 0.9 mL / min. Controlling the flow rate of the carrier gas within the above preferred range is beneficial to the reduction of the sample.

[0032] According to some preferred embodiments of the present invention, the temperature of the roasting is 300 - 1000 °C. For example, it can be 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C and other typical but non-limiting roasting temperatures or the range between them. Preferably, the temperature of the roasting is 500 - 900 °C; preferably, the heating rate is 0.5 - 15 °C / min, preferably 3 - 9 °C / min. For example, it can be 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, etc. Preferably, the roasting time is 30 - 300 min, preferably 60 - 180 min.

[0033] The present invention has no special requirements for the equipment used for roasting, and it can be selected according to experimental or industrial needs. For example, in the laboratory, a tube furnace can be used for the roasting.

[0034] According to some preferred embodiments of the present invention, the transition metal sulfide and the non-metal source are evenly paved and placed on a porcelain boat respectively, and then moved into a tubular furnace and covered and pressed tightly, with the non-metal source upstream. A carrier gas is introduced, and then calcination is carried out. The purpose of covering and pressing tightly is to prevent the sample from being blown away, and quartz wool can be used for covering.

[0035] In the present invention, there is no special requirement for the S vacancy content in the transition metal sulfide containing S vacancies, as long as it contains S vacancies, it can assist in the preparation of a composite catalyst in which non-metal element doping induces rich S vacancies in the transition metal sulfide by means of high-temperature calcination and anion-cation exchange method. The present invention also has no special limitation on the source of the transition metal sulfide containing S vacancies, and it can be prepared by any known method in the art.

[0036] According to some preferred embodiments of the present invention, the preparation method of the transition metal sulfide containing S vacancies includes:

[0037] (1) Mix the transition metal oxide and the sulfur source, carry out a hydrothermal reaction, and then carry out washing and drying;

[0038] (2) Contact the product obtained in step (1) with a reducing agent.

[0039] The present invention has no special limitation on the source of the transition metal oxide, which can be commercially purchased or prepared by conventional methods in the art. The present invention also has no special limitation on the type of the sulfur source, as long as it can provide sulfur element. Preferably, the sulfur source is thiourea.

[0040] According to some preferred embodiments of the present invention, the mass ratio of the transition metal oxide to the sulfur source is 1:(1 - 2), for example, typical but non-limiting mass ratios such as 1:1, 1:1.2, 1:1.3, 1:1.5, 1:1.7, 1:1.8, 1:2, etc.

[0041] The present invention has no special limitation on the conditions of the hydrothermal reaction, as long as it can form a transition metal sulfide. Preferably, the conditions of the hydrothermal reaction include: the temperature is 180 - 250 °C, and the time is 10 - 20 h.

[0042] The present invention has no special limitation on the operation mode and conditions of the washing and drying, and can be carried out in a conventional manner in the art to remove unreacted raw materials. Preferably, the drying temperature is 50 - 100 °C.

[0043] In the present invention, by contacting the product obtained in step (1) with a reducing agent, the transition metal element in the transition metal sulfide is reduced, thereby generating S vacancies in the transition metal sulfide. The scope of selection of the reducing agent in the present invention is relatively wide and can be a conventional selection in the art.

[0044] To facilitate the control of S vacancies in the transition metal sulfide, preferably, step (2) includes: contacting the product obtained in step (1) with a reducing agent, and the reducing agent is NaBH 4 .

[0045] According to some preferred embodiments of the present invention, the reducing agent is provided by an aqueous solution of the reducing agent, and the concentration of the aqueous solution of the reducing agent is 2-12 wt%.

[0046] Preferably, relative to 1 g of the product obtained in step (1), the amount of the aqueous solution of the reducing agent used is 100-400 mL.

[0047] According to some preferred embodiments of the present invention, the contact in step (2) is carried out under ultrasonic or stirring conditions, and preferably, the contact time is 1-3 h.

[0048] According to the present invention, step (2) further includes: performing solid-liquid separation, washing, and drying on the product obtained by the contact. The solid-liquid separation can be carried out by filtration or centrifugal separation, for example. The washing and drying can be carried out in a conventional manner in the art as long as the solvent in the product can be removed.

[0049] According to some particularly preferred embodiments of the present invention, the preparation method of the composite catalyst includes:

[0050] (1) Mixing a transition metal oxide with a sulfur source, carrying out a hydrothermal reaction, and then performing washing and drying;

[0051] (2) Contacting the product obtained in step (1) with a reducing agent to obtain a transition metal sulfide containing S vacancies;

[0052] (3) Roasting the transition metal sulfide containing S vacancies with a non-metal source in the presence of a carrier gas; the non-metal source is selected from at least one of a phosphorus source, a carbon source, a nitrogen source, and a selenium source; the mass ratio of the non-metal source to the transition metal sulfide containing S vacancies is 3-20:1.

[0053] Among them, along the flow direction of the carrier gas, the non-metal source is placed upstream of the transition metal sulfide containing S vacancies. Relative to 1 g of the non-metal source, the flow rate of the carrier gas is 0.3-0.9 mL / min, the roasting temperature is 300-1000 °C, the heating rate is 3-9 °C / min, and the time is 30-300 min.

[0054] The second aspect of the present invention provides the composite catalyst prepared by the above preparation method.

[0055] The third aspect of the present invention provides an electrolytic water hydrogen evolution catalytic electrode, which comprises a conductive substrate and a catalytic material composite on the surface of the conductive substrate, and the catalytic material is the composite catalyst described in the second aspect.

[0056] The present invention has a wide selection range for the conductive substrate, and any conductive substrate that can be used for electrolytic water electrodes in the art can be applied to the present invention. Preferably, the conductive substrate is selected from modified or unmodified carbon paper. The modified carbon paper can be hydrophobic modified carbon paper or hydrophilic modified carbon paper, such as at least one of 20% hydrophobic carbon paper, 5% hydrophobic carbon paper, 5% hydrophilic carbon paper and 20% hydrophilic carbon paper.

[0057] Preferably, based on the surface area of the electrode, the loading amount of the catalytic material is 0.5 - 3 mg / cm 2 , preferably 1 - 2 mg / cm 2 .

[0058] Preferably, the electrode comprises a conductive substrate, and a catalytic material and a diaphragm composite on the surface of the conductive substrate. The present invention has no particular requirement for the specific selection of the diaphragm, and those skilled in the art can select according to actual needs. For example, it can be a Nafion membrane. The present invention also has no particular limitation on the thickness of the diaphragm.

[0059] According to some preferred embodiments of the present invention, the preparation method of the electrolytic water hydrogen evolution catalytic electrode comprises: dispersing the catalytic material and the diaphragm in an organic solvent to obtain a dispersion; then loading the dispersion on the surface of the conductive substrate and drying.

[0060] Preferably, the organic solvent is alcohol, such as methanol and / or ethanol, preferably ethanol. The present invention has no particular limitation on the concentration of the dispersion, as long as the catalytic material and the diaphragm can be fully dispersed. Those skilled in the art can select according to actual needs. Preferably, the dispersion is carried out under ultrasonic conditions.

[0061] According to the present invention, the method of loading the dispersion on the surface of the conductive substrate can be, for example, dropping, spraying, etc. The present invention has no particular limitation on this. The loading can also be carried out once or multiple times to meet the loading amount of the catalytic material.

[0062] According to the present invention, preferably, the drying is carried out under the irradiation of an infrared lamp.

[0063] The fourth aspect of the present invention provides a method for hydrogen evolution by electrolyzing water, the method comprising: under the conditions of electrolyzing water, using the electrolytic water hydrogen evolution catalytic electrode described in the third aspect as the working electrode to carry out the electrolytic water reaction.

[0064] The present invention will be described in detail below through examples.

[0065] In the following examples and comparative examples, unless otherwise specified, the raw materials used are all commercially available.

[0066] The instrument used for electron spin paramagnetic resonance spectroscopy (EPR) is a Bruker band continuous wave EPR spectrometer. The specific test parameters are as follows: central magnetic field 3500.00 G; sweep field width 200.00 G; sweep field time 30.00 s; microwave power 19.45 mW; modulation amplitude 1.000 G; conversion time 40.00 ms. The paramagnetic sample is placed in a rectangular cavity resonator with a frequency of 9.852508 GHz. The reflected microwave enters the detector through the circulator, and the resonance information can be calculated according to the absorption amount of the microwave radiation.

[0067] The following preparation examples are used to illustrate the preparation of transition metal sulfides containing S vacancies in the present invention.

[0068] Preparation Example 1

[0069] Ammonium molybdate tetrahydrate and ethylenediamine with a mass ratio of 2:1.3 were dispersed in deionized water, and then the obtained solution was slowly added dropwise to 1 M HCl aqueous solution under magnetic stirring until the pH was adjusted to 4.5. It was placed in a water bath at 55 °C and slowly stirred for 3 h. The product was washed clean with anhydrous ethanol and then placed in a vacuum drying oven at 50 °C until the sample was completely dried, and the obtained product was MoO 3 .

[0070] Further, MoO 3 and thiourea with a mass ratio of 2:3.5 were dispersed in deionized water, and then the obtained homogeneous solution was placed in a 50 mL polytetrafluoroethylene inner liner and allowed to react continuously at 210 °C for 14 h. The black material cooled to room temperature was centrifuged, washed alternately with water and ethanol, and then the product was filtered by suction. Finally, it was placed in a vacuum drying oven at 65 °C until the sample was completely dried to obtain MoS 2 .

[0071] Disperse 0.3 g of MoS 2 sample into 100 mL of 8 wt% NaBH 4In the solution, ultrasonic for 1 h at room temperature. Centrifuge the obtained product, wash it several times alternately with water and ethanol, then directly filter the product by suction, and finally place it in a vacuum drying oven at 65 °C until the sample is completely dried to obtain a transition metal sulfide containing S vacancies. The prepared sulfide is denoted as Sv-MoS 2 .

[0072] Preparation Example 2

[0073] Disperse tungsten chloride and ethylenediamine with a mass ratio of 2:1.5 in deionized water, then slowly add 1 M HCl aqueous solution dropwise to the obtained solution under magnetic stirring until the pH is adjusted to 4.5, and place it in a water bath at 55 °C and stir slowly for 3 h. Wash the product with anhydrous ethanol, and then place it in a vacuum drying oven at 50 °C until the sample is completely dried to obtain the product WO 2 .

[0074] Further, disperse WO 2 and thiourea with a mass ratio of 2:3 in deionized water, then place the obtained homogeneous solution in a 50 mL polytetrafluoroethylene inner liner and allow it to react continuously at 210 °C for 14 h. Centrifuge the black material cooled to room temperature, wash it alternately with water and ethanol, then filter the product by suction, and finally place it in a vacuum drying oven at 65 °C until the sample is completely dried to obtain WS 2 .

[0075] Disperse 0.5 g of WS 2 sample into 150 mL of 5 wt% NaBH 4 solution, ultrasonic for 1 h at room temperature. Centrifuge the obtained product, wash it several times alternately with water and ethanol, then directly filter the product by suction, and finally place it in a vacuum drying oven at 65 °C until the sample is completely dried to obtain a transition metal sulfide containing S vacancies. The prepared sulfide is denoted as Sv-WS 2 .

[0076] Comparative Preparation Example 1

[0077] Disperse ammonium molybdate tetrahydrate and ethylenediamine with a mass ratio of 2:1.3 in deionized water, then slowly add 1 M HCl aqueous solution dropwise to the obtained solution under magnetic stirring until the pH is adjusted to 4.5, and place it in a water bath at 55 °C and stir slowly for 3 h. Wash the product with anhydrous ethanol, and then place it in a vacuum drying oven at 50 °C until the sample is completely dried to obtain the product MoO 3 .

[0078] Further, disperse MoO 3and thiourea were dispersed in deionized water, and then the obtained homogeneous solution was placed in a 50 mL Teflon liner and allowed to react continuously at 210 °C for 14 h. The black material cooled to room temperature was centrifuged, washed alternately with water and ethanol, and then the product was filtered by suction. Finally, it was placed in a vacuum drying oven at 65 °C until the sample was completely dried to obtain MoS 2 .

[0079] The following examples are used to illustrate the preparation of the composite catalyst in the present invention.

[0080] Example 1

[0081] Phosphoric acid in terms of P element and Sv-MoS 2 were evenly spread on a porcelain boat according to a mass ratio of 9:1, and then moved into a tube furnace and covered and pressed tightly with quartz wool. The non-metal source was upstream, and N 2 was introduced. The flow rate of the carrier gas was 0.5 mL / min relative to 1 g of the non-metal source. The reaction furnace was started, and the temperature was raised to 800 °C at a heating rate of 6 °C / min for calcination, and the calcination time was 120 min to obtain the composite catalyst S1. The composite catalyst S1 was observed by transmission electron microscopy, and the composite catalyst presented a nanotube shape, and Mo, S, and P elements were highly dispersed on it.

[0082] Example 2

[0083] Disodium hydrogen phosphate in terms of P element and Sv-MoS 2 were evenly spread on a porcelain boat according to a mass ratio of 9:1, and then moved into a tube furnace and covered and pressed tightly with quartz wool. The non-metal source was upstream, and N 2 was introduced. The flow rate of the carrier gas was 0.3 mL / min relative to 1 g of the non-metal source. The reaction furnace was started, and the temperature was raised to 900 °C at a heating rate of 9 °C / min for calcination, and the calcination time was 180 min to obtain the composite catalyst S2.

[0084] Example 3

[0085] Sodium hypophosphite in terms of P element and Sv-MoS 2 were evenly spread on a porcelain boat according to a mass ratio of 9:1, and then moved into a tube furnace and covered and pressed tightly. The non-metal source was upstream, and H 2 / N 2 (volume ratio 5:95) was introduced. The flow rate of the carrier gas was 0.7 mL / min relative to 1 g of the non-metal source. The reaction furnace was started, and the temperature was raised to 900 °C at a heating rate of 3 °C / min for calcination, and the calcination time was 120 min to obtain the composite catalyst denoted as S3.

[0086] Example 4

[0087] Glucose in terms of C element and Sv-MoS 2 were evenly paved on a porcelain boat according to a mass ratio of 7:1, then transferred into a tubular furnace, covered and compacted. The non-metal source was placed upstream, and H 2 / N 2 (volume ratio 5:95) was introduced. The flow rate of the carrier gas was 0.9 mL / min relative to 1 g of the non-metal source. The reaction furnace was started, heated to 700 °C at a heating rate of 7 °C / min for calcination, and the calcination time was 90 min to obtain a composite catalyst denoted as S4.

[0088] Example 5

[0089] Ethylenediamine in terms of N element and Sv-MoS 2 were evenly paved on a porcelain boat according to a mass ratio of 9:1, then transferred into a tubular furnace, covered and compacted. The non-metal source was placed upstream, and H 2 / N 2 (volume ratio 5:95) was introduced. The flow rate of the carrier gas was 0.5 mL / min relative to 1 g of the non-metal source. The reaction furnace was started, heated to 500 °C at a heating rate of 6 °C / min for calcination, and the calcination time was 60 min to obtain a composite catalyst denoted as S5.

[0090] Example 6

[0091] According to the method of Example 1, except that the mass ratio of the phosphorus source in terms of P element to Sv-MoS 2 was 10:1. A composite catalyst denoted as S6 was obtained.

[0092] Example 7

[0093] According to the method of Example 1, except that the mass ratio of the phosphorus source in terms of P element to Sv-MoS 2 was 5:1. A composite catalyst denoted as S7 was obtained.

[0094] Example 8

[0095] According to the method of Example 1, except that an equal mass of Sv-WS 2 was used to replace Sv-MoS 2 . A composite catalyst denoted as S8 was obtained.

[0096] Example 9

[0097] According to the method of Example 1, except that the calcination conditions were: heated to 800 °C at a heating rate of 9 °C / min, and the calcination time was 180 min to obtain a composite catalyst denoted as S9.

[0098] Comparative Example 1

[0099] According to the method of Example 1, except that an equal mass of the aforementioned MoS 2 is used to replace Sv-MoS 2 . The obtained composite catalyst is denoted as DS1.

[0100] Comparative Example 2

[0101] The Sv-MoS prepared in Preparation Example 1 2 is directly used as a catalyst and denoted as DS2.

[0102] Test Example:

[0103] (1) Electron spin resonance spectroscopy (EPR) test.

[0104] The materials obtained in Example 1, Comparative Example 1, Preparation Example 1 and Comparative Preparation Example 1 above were subjected to EPR test, and the results are as Figure 1 shown. It can be seen that the content of S vacancies in the composite catalyst prepared in the examples of the present invention is further increased. The results show that molybdenum disulfide containing S vacancies is more conducive to the induction of vacancies by non-metallic elements, improving the active area and increasing the active sites, thereby significantly improving its electrocatalytic HER performance.

[0105] (2) Electrochemical performance test.

[0106] All the electrochemical tests used in the present invention were carried out on a VSP-300 type electrochemical workstation with a three-electrode system. Among them, the carbon paper, graphite electrode and calomel electrode (SCE) loaded with the sample were used as the working electrode, counter electrode and reference electrode in the three electrodes, respectively.

[0107] Preparation of the working electrode: First, weigh 4 mg of the sample material with a balance and put it into a small volumetric flask. Secondly, use a pipette to take 360 μL of absolute ethanol and add it to the volumetric flask of the sample. Ultrasonic it in an ultrasonic cleaner for several minutes to make it evenly dispersed. Add 40 μL of Nafion membrane solution and continue ultrasonic until the sample is evenly dispersed in the solution. Finally, use a pipette to take 50 μL of the ink and gradually drop it on a 1×1 cm carbon paper, a total of 6 times, and dry it under an infrared lamp for standby. The loading amount is 1.5 mg / cm 2 .

[0108] The test methods used in the present invention to evaluate the catalytic performance of the sample include: linear sweep voltammetry (LSV) and chronopotentiometry (CP) electrocatalytic test methods.

[0109] The linear sweep (LSV) test is the change of voltage with current within a certain time during the hydrogen evolution reaction (HER) test. Test conditions: The scanning voltage range is 0 - 1 V, and the scanning rate is 2 mV / s. The results are shown in Table 1.

[0110] Table 1

[0111]

[0112]

[0113] Figure 2 (a) is the Tafel slope curve of Example 1 (MoP@Sv-MoS 2 ), Comparative Example 1 (MoP@MoS 2 ), Preparation Example 1 (Sv-MoS 2 ), and Comparative Preparation Example 1 (MoS 2 ). It can be seen from the figure that the Tafel slope values of all composite materials show a decreasing trend, indicating good performance. Among them, the Tafel slope of the MoP@Sv-MoS 2 composite material is 60 mV·dec -1 , indicating a relatively fast hydrogen evolution rate.

[0114] Figure 2 (b) is the test of the active area of the composite materials in Example 1, Comparative Example 1, Preparation Example 1, and Comparative Preparation Example 1. It can be seen from the figure that within the voltage range of 0.22 - 0.27 V (vs. RHE), cyclic voltammetry tests were performed on the materials at different scan rates. The results show that the C 2 value of the MoP@Sv-MoS dl sample is the largest (20 mF·cm -2 ), indicating that MoP@Sv-MoS 2 has the largest active area, indicating that the increased active sites are consistent with the electrochemically effective active area, improving the hydrogen evolution performance of the material.

[0115] The electrochemical stability of the materials was tested by chronopotentiometry (CP); in the electrolyte, at a certain overpotential, the voltage change was observed after continuous operation for a certain period of time. The chronopotentiometry curve of the MoP@Sv-MoS 2 composite material in Example 1 is as shown in Figure 2 (c). It can be seen from the figure that when the current of the sample is 10 mA·cm -2 , there is no change in the voltage after 24 hours of testing.

[0116] The change in the LSV curve before and after 1000 CV cycles was investigated. The cyclic voltammetry test curve of the MoP@Sv-MoS 2 composite material in Example 1 under long-term cycling is as shown in Figure 2 (d). It can be seen from the figure that the polarization curve results after 1000 cycles show no obvious change in the overpotential.

[0117] CombiningFigure 2 (c) and Figure 2 As can be seen from the results of (d), the composite material prepared in the embodiment of the present invention has good electrochemical stability.

[0118] Combined with Table 1 and Figure 2 the results, it can be seen that in the embodiment of the present invention, the S vacancy is used to assist the preparation of a composite catalyst rich in sulfur vacancies of a non-metal element doped induced transition metal sulfide by high-temperature calcination of the anion-cation exchange method, which can effectively adjust the electronic structure of the catalyst. By comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that the catalyst prepared by the preparation method provided by the present invention has a lower overpotential and a lower Tafel slope value, and the HER activity is significantly improved.

[0119] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite catalyst, characterized in that: The preparation method comprises: in the presence of a carrier gas, calcining a transition metal sulfide containing S vacancies and a non-metal source; the non-metal source is selected from at least one of a phosphorus source, a carbon source, a nitrogen source and a selenium source; Wherein, along the flow direction of the carrier gas, the non-metal source is placed upstream of the transition metal sulfide containing S vacancies.

2. The preparation method according to claim 1, wherein The mass ratio of the non-metallic source to the transition metal sulfide containing S vacancies, calculated as an element, is 3-20:1, preferably 5-10:

1.

3. The preparation method according to claim 1 or 2, wherein The transition metal in the transition metal sulfide containing S vacancies is selected from at least one of Group VIB, Group VIIB, Group VIII and Group IB metal elements, preferably at least one of Fe, Co, Ni, W, Mo, Mn and Cu, more preferably Mo and / or W, and more preferably Mo.

4. The preparation method according to any one of claims 1 to 3, wherein The phosphorus source is selected from at least one of phosphoric acid, sodium hypophosphite, disodium hydrogen phosphate and diammonium phosphate; and / or, The nitrogen source is selected from at least one of ethylenediamine, triethylamine and N,N-dimethylethyleneamine; and / or, The carbon source is selected from at least one of glucose, sodium acetate, dicyandiamide and polyvinylidene fluoride; and / or, The selenium source is selected from at least one of selenium powder, sodium selenite, ammonium selenate and tin diselenide.

5. The preparation method according to any one of claims 1 to 4, wherein: The carrier gas is selected from at least one of nitrogen, argon and hydrogen; Preferably, the flow rate of the carrier gas is 0.1-1.5 mL / min relative to 1 g of the non-metal source.

6. The preparation method according to any one of claims 1 to 5, wherein: The calcination temperature is 300-1000° C., preferably 500-900° C., the heating rate is 0.5-15° C. / min, preferably 3-9° C. / min, and the calcination time is 30-300 min, preferably 60-180 min.

7. The preparation method according to any one of claims 1 to 6, wherein: The preparation method of the transition metal sulfide containing S vacancies comprises: (1) mixing a transition metal oxide with a sulfur source, performing a hydrothermal reaction, and then washing and drying; (2) contacting the product obtained in step (1) with a reducing agent; Preferably, the sulfur source is thiourea; Preferably, the mass ratio of the transition metal oxide to the sulfur source is 1:(1-2); Preferably, the conditions of the hydrothermal reaction include: temperature of 180-250°C and time of 10-20h; Preferably, the reducing agent is NaBH4.

8. A composite catalyst obtained by the preparation method described in any one of claims 1 to 7.

9. A catalytic electrode for hydrogen evolution by water electrolysis, characterized in that: The electrode comprises a conductive substrate, and a catalytic material composited on the surface of the conductive substrate, wherein the catalytic material is the composite catalyst according to claim 8; Preferably, the conductive substrate is selected from modified or unmodified carbon paper; the modified carbon paper is preferably at least one of 20% hydrophobic carbon paper, 5% hydrophobic carbon paper, 5% hydrophilic carbon paper and 20% hydrophilic carbon paper; Preferably, based on the surface area of ​​the electrode, the loading amount of the catalytic material is 0.5-3 mg / cm 2 , preferably 1-2 mg / cm 2 .

10. A method for hydrogen evolution by electrolysis of water, characterized in that: The method comprises: under water electrolysis conditions, using the water electrolysis hydrogen evolution catalytic electrode according to claim 9 as a working electrode to perform a water electrolysis reaction.

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