A multi-level hydrogen evolution electrode material of MoS2 loaded N-doped carbon and a preparation method thereof

Abstract

The present invention belongs to the field of hydrogen energy and discloses a multi-level hydrogen evolution electrode material loaded with N-doped carbon on MoS2 and a preparation method thereof. The present invention uses MOF nanocones as templates to prepare nitrogen-doped carbon to increase the effective surface area and catalytic active sites of MoS2 loading, thereby preparing a MoS2-based multi-level structure composite catalyst with good electrocatalytic hydrogen evolution activity. The self-supporting NC@MoS2 / CC composite electrode material prepared by the present invention has a multi-level porous structure constructed of interlaced nanosheets / nitrogen-doped carbon. When used for electrocatalytic hydrogen evolution reaction under acidic conditions, it can reach 10mA·cm ‑2 The overpotential of the current density is only 181.2mV, and the Tafel slope is 85.86mV·dec ‑1 It can effectively improve the catalytic activity and catalytic stability of the catalytic electrode.

Description

Technical Field

[0001] The present invention belongs to the field of hydrogen energy, and in particular relates to a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material and a preparation method thereof. Background Art

[0002] As a clean, stable and renewable energy source, hydrogen energy has great potential to become a substitute for fossil fuels. The development of hydrogen energy is regarded as an important route to solve the energy crisis. Hydrogen energy has the advantages of high combustion calorific value, wide range of raw materials, single combustion products, and zero carbon emissions. Efficient production of hydrogen is the key to meeting the large-scale commercial application of hydrogen energy. Currently, there are mainly catalytic reforming hydrogen production, biomass / microbial hydrogen production, photocatalytic hydrogen production, and water electrolysis hydrogen production. Water electrolysis hydrogen production is an efficient way to convert electrical energy into hydrogen energy. Precious metal-based catalysts represented by Pt are currently the best performing hydrogen evolution reaction (HER) electrocatalysts, but due to limited reserves and high costs, large-scale application is difficult to achieve. Therefore, the development of low-cost, high-efficiency, and structurally stable non-precious metal-based catalysts is the research focus of electrocatalytic hydrogen production.

[0003] Molybdenum disulfide (MoS2), as a typical representative of two-dimensional layered transition metal sulfides, has the characteristics of large specific surface area, low preparation cost, and stable chemical properties. However, MoS2 has poor intrinsic conductivity, and the active sites on the crystal surface are only distributed at the edge or defect positions. Conventionally prepared crystalline materials cannot achieve high-performance hydrogen evolution activity. Therefore, it is necessary to achieve a dual increase in the conductivity and number of active sites of MoS2 crystals through effective material structure design, which is of great significance for the development of low-cost HER electrocatalysts. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a method for preparing a multi-level hydrogen evolution electrode material of MoS2 loaded with N-doped carbon. The catalytic electrode material prepared by this method has good electrohydrogen evolution activity and catalytic stability, the material preparation operation is simple, the micro-nano structure is controllable, and it is easy to industrialize.

[0005] Another object of the present invention is to provide a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material prepared by the above method.

[0006] The purpose of the present invention is achieved through the following solutions:

[0007] A method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material comprises the following steps:

[0008] (1) cut the conductive carbon cloth into a certain shape (the size of the carbon cloth can be adjusted according to the size of the reactor), soak it in an alcohol solution, remove the surface organic impurities by ultrasonic, then rinse with deionized water, then soak it in a potassium permanganate solution at room temperature, after taking out the carbon cloth, wash and dry it;

[0009] (2) stir 2-methylimidazole in water to form solution A; stir cobalt nitrate hexahydrate in water to form solution B; after both A and B solutions are completely dissolved, pour solution B into solution A, mix and stir until uniform, then place the dried carbon cloth from step (1) flat in the mixed solution for constant temperature soaking; take out the carbon cloth, wash and dry it to obtain cobalt-based MOF loaded carbon cloth, denoted as Co-MOF;

[0010] (3) place Co-MOF in a tube furnace, perform constant temperature heat treatment under Ar gas environment, after cooling, immerse it in an acid solution to remove excess Co ions, then wash and dry it to obtain Co, N co-doped carbon, denoted as Co-NC / CC;

[0011] (4) add HCl solution to the mixed solution prepared from FeCl3, immerse Co-NC / CC in the mixed solution for 24 h to remove Co ions, then wash and dry it to obtain NC / CC precursor;

[0012] (5) stir ammonium molybdate tetrahydrate and thiourea in water to obtain a mixed solution, take the mixed solution and the NC / CC precursor obtained in step (4) into a reaction kettle to perform hydrothermal reaction, after the reaction is completed, cool to room temperature, take out the carbon cloth, wash and dry it to obtain MoS2 loaded N-doped carbon multi-level hydrogen evolution electrode material, denoted as Co-NC@MoS2 / CC.

[0013] The alcohol solution in step (1) is any one of ethanol or isopropanol, preferably 95% ethanol;

[0014] The mass molar concentration of the potassium permanganate solution in step (1) is 0.5 M, and the soaking time is 1-2 h;

[0015] The molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate in step (2) is 8:1;

[0016] The constant temperature soaking in step (2) refers to soaking at 25℃ for 6-8 h;

[0017] The Ar gas flow in step (3) is preferably 50 sccm;

[0018] The constant temperature heat treatment in step (3) refers to heating to 700℃, holding at 700℃ for 1 h, and the heating rate is 2-3℃·min -1 ;

[0019] The acid solution in step (3) is an HCl solution; preferably a 1M HCl solution; and the immersion time is 12-24h;

[0020] The mass molar concentration of the HCl solution in step (4) is 1M; the mass molar concentration of the FeCl3 solution is 3M; and the volume ratio of the HCl solution to the FeCl3 solution is 1:100;

[0021] The immersion time in step (4) is 12-24h;

[0022] The molar ratio of the ammonium molybdate tetrahydrate to the thiourea in step (5) is 1:15;

[0023] The reaction temperature of the hydrothermal reaction in step (5) is 180℃, and the reaction time is 9-12h;

[0024] The washing in steps (1)-(5) means rinsing with deionized water; and the drying means drying at 50-80℃ for 6-12h.

[0025] A MoS2-loaded N-doped carbon multilayer hydrogen evolution electrode material prepared by the above method.

[0026] The inventive mechanism of the present application is as follows:

[0027] The present application constructs a MOF-based nitrogen-doped porous carbon as a multilayer conductive network based on a three-dimensional conductive carbon cloth (CC), and then realizes in-situ growth of ultra-fine MoS2 vertically staggered structure nanosheets on the surface, realizes double-effect improvement of electron migration efficiency and intrinsic catalytic activity, and realizes its application in the field of electrocatalytic hydrogen evolution electrodes. Among them, the construction of a conductive network with a multilayer structure and the compounding with MoS2 can effectively improve the electron migration efficiency of the catalytic electrode, thereby improving the poor intrinsic conductivity of MoS2. At the same time, through the controllable synthesis of ultra-small vertically staggered MoS2 nanosheets, a catalyst interface with a porous structure is constructed, which can increase the interface between the catalytically active material and the electrolyte, and the ultra-small MoS2 nanosheets can increase the edge structure and the density of crystal defects, thereby effectively improving the active site density of the active material. Therefore, the present application designs and prepares a composite structure with a multilayer conductive network and a rich electrochemical active center on a conductive substrate, and a MoS2-loaded N-doped carbon multilayer hydrogen evolution electrode material is prepared, which realizes its application in the field of electrocatalytic hydrogen evolution and has important significance.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0029] The self-standing NC@MoS2 / CC composite electrode material for an electrocatalytic hydrogen evolution electrode prepared by the method of the application is composed of two phases of nitrogen-doped porous carbon and MoS2 interlaced structures uniformly grown on the surface of the nitrogen-doped porous carbon, and has not only the high conductivity characteristics of carbon materials, but also the excellent hydrogen evolution performance of MoS2, and the small nanosheet is conducive to the charge transfer and active site exposure.

[0030] (1) The application uses three-dimensional carbon cloth as a growth substrate, obtains N-doped porous carbon through in-situ carbonization and ion exchange of a cobalt-based MOF nanotower, and then generates a MoS2 coating layer with a nanosheet interlaced structure on the surface of the N-doped porous carbon in-situ, to form a multi-level porous structure, which, when used for an acidic electrocatalytic hydrogen evolution reaction, has a current density of 10 mA·cm -2 , and a overpotential of only 181.2 mV and a Tafel slope of 85.86 mV·dec -1 , and has good electrochemical hydrogen evolution catalytic performance and stability.

[0031] (2) The self-standing NC@MoS2 / CC composite electrode material for an electrocatalytic hydrogen evolution electrode prepared by the method of the application has a multi-level porous structure constructed by interlaced nanosheets and nitrogen-doped carbon, and the interlaced nanosheet structure closely connected with the nitrogen-doped carbon is conducive to electron transfer, and the porous structure can improve the contact area of the electrode material and the electrolyte. The interlaced structure of small sheet nanosheets can obtain more interface defects and active sites, enhance the intrinsic activity of the material, and thus obtain high electrochemical hydrogen evolution performance.

[0032] (3) The self-standing NC@MoS2 / CC composite electrode material for an electrocatalytic hydrogen evolution electrode prepared by the method of the application can obtain excellent reaction gas mass transfer efficiency and electrochemical stability due to the small sheet nanosheet interlaced structure and the rich micropores, and can maintain stable performance in a long-time hydrogen evolution reaction.

[0033] (4) The method of the application combines normal temperature reaction and hydrothermal synthesis, is simple to operate, low in cost, and suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The XRD graph of the NC@MoS2 / CC sample prepared by the application;

[0035] Figure 2 The SEM graph of the NC@MoS2 / CC sample prepared by the application; the left graph is a scanning electron microscope graph with a magnification of 5000 times, and the right graph is a scanning electron microscope graph with a magnification of 20000 times;

[0036] Figure 3 The LSV curve of the electrochemical hydrogen evolution process of the NC@MoS2 / CC sample prepared by the application;

[0037] Figure 4 Tafel slope of the NC@MoS2 / CC sample prepared in the application in the process of electrochemical hydrogen evolution;

[0038] Figure 5 Long cycle stability curve of the NC@MoS2 / CC sample prepared in the application. DETAILED DESCRIPTION

[0039] The application will be described in further detail below with reference to the examples and drawings, but the embodiments of the application are not limited thereto. In the examples, the specific conditions not mentioned are carried out according to the conventional conditions or the conditions recommended by the manufacturers. The reagents or instruments used are not mentioned by the manufacturers, and are all conventional products that can be purchased on the market.

[0040] Example 1

[0041] (1) The conductive carbon cloth was cut into a shape of 3*2 cm, immersed in 95% ethanol for ultrasonic treatment for 15 min to remove the surface organic impurities, and then washed with deionized water; then immersed in 30 mL of 0.5M potassium permanganate solution at room temperature for 1 h to improve the surface hydrophilicity, and then washed with deionized water, and dried at 50℃ for 6 h;

[0042] (2) 2-methylimidazole (1313.6 mg) was stirred and dissolved in 40 mL of deionized water to form solution A; cobalt nitrate hexahydrate (582.06 mg) was stirred and dissolved in 40 mL of deionized water to form solution B; after the A and B solutions were completely dissolved, solution B was poured into solution A, and stirred for 5 min to obtain a uniform solution; the dried carbon cloth of step (1) was placed flat in the mixed solution and soaked at 25℃ for 6 h; the carbon cloth was taken out, washed with deionized water, and dried at 50℃ for 12 h to obtain a cobalt-based MOF loaded carbon cloth, denoted as Co-MOF;

[0043] (3) The Co-MOF was placed in a tube furnace, and heated to 700℃ (heating rate 2℃·min -1 ) under Ar gas environment (50 sccm), and heat treated at 700℃ for 1 h; after cooling, the material was immersed in 30 mL of 1M HCl solution for 12 h to remove excess Co ions, washed with deionized water, and placed in a 50℃ oven for drying for 12 h to obtain Co, N co-doped carbon, denoted as Co-NC / CC;

[0044] (4) 1M HCl (1 mL) was added to 3M FeCl3 (100 mL) solution, and the Co-NC / CC was immersed in the solution for 24 h to remove Co ions in the carbon skeleton, then washed with deionized water, and placed in a 50℃ oven for drying for 12 h to obtain an NC / CC precursor;

[0045] (5) stirring ammonium molybdate tetrahydrate (519 mg) and thiourea (456.5 mg) in 45 mL of deionized water to obtain a mixed solution, taking 40 mL of the mixed solution (the amount of the mixed solution can be adjusted according to the requirements of the reactor) and the NC / CC precursor obtained in step (4) into a reaction kettle to perform a hydrothermal reaction, the reaction temperature is 180 DEG C, and the reaction is performed for 9 h, and after the reaction is completed, the reaction is cooled to room temperature; the carbon cloth loaded with the active substance is taken out, washed, and dried at 50 DEG C for 12 h to obtain an MoS2-loaded N-doped carbon multi-layer hydrogen evolution electrode material, denoted as Co-NC@MoS2 / CC.

[0046] Figure 1 The XRD pattern of the NC@MoS2 / CC sample prepared in the application can be known from which the sample has typical MoS2 crystal characteristic peaks, proving the successful preparation of the N-doped porous carbon surface MoS2 active substance.

[0047] From the SEM image of the NC@MoS2 / CC sample prepared in the application, it can be seen that the application uses a three-dimensional carbon cloth as a growth substrate, and through in-situ carbonization and ion exchange of the cobalt-based MOF nanotaper, an N-doped porous carbon is obtained, and then an MoS2 coating layer with a nanosheet staggered structure is generated in-situ on the surface thereof, forming a multi-layered porous structure. Figure 2

[0048] Figure 3 and Figure 4 The LSV curve and the Tafel slope of the electrochemical hydrogen evolution process of the NC@MoS2 / CC sample prepared in the application can be known from which when the self-standing NC@MoS2 / CC composite electrode material prepared in the application is used as an acidic condition electrocatalytic hydrogen evolution reaction, the overpotential required to reach a current density of 10 mA·cm-2 is only 181.2 mV, and the Tafel slope is 85.86 mV·dec-1, and the self-standing NC@MoS2 / CC composite electrode material has good electrochemical hydrogen evolution catalytic performance and stability. -2 -1

[0049] Figure 5 The long cycle stability curve of the NC@MoS2 / CC sample prepared in the application can be known from which the self-standing composite electrode material exhibits good electrocatalytic hydrogen evolution stability in the stability test of 12 hours, and does not show obvious performance attenuation.

[0050] The above examples are preferred embodiments of the application, but the embodiments of the application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application shall be equivalent replacement methods, and all shall be included in the protection scope of the application.​​​

Claims

1. A method for preparing a multi-level hydrogen evolution electrode material loaded with MoS2 and N-doped carbon, characterized in that The following steps are involved: (1) Cut the conductive carbon cloth, soak it in an alcohol solution and ultrasonically remove organic impurities on the surface. After taking it out, rinse it with deionized water, then soak it in potassium permanganate solution at room temperature. After taking it out, wash it and dry it. (2) 2-Methylimidazole is stirred and dissolved in water to form solution A; cobalt nitrate hexahydrate is stirred and dissolved in water to form solution B; after solutions A and B are completely dissolved, solution B is poured into solution A, mixed and stirred evenly, and the carbon cloth dried in step (1) is placed flat in the mixed solution and soaked at a constant temperature; the carbon cloth is taken out, washed, and dried to obtain a cobalt-based MOF-loaded carbon cloth, which is recorded as Co-MOF; (3) The Co-MOF was placed in a tube furnace and subjected to constant temperature heat treatment in an Ar gas environment. After cooling, it was taken out and immersed in an acid solution to remove excess Co ions. After removal, it was washed and dried to obtain Co, N co-doped carbon, which was recorded as Co-NC / CC. (4) Adding HCl solution to FeCl3 solution to prepare a mixed solution, immersing Co-NC / CC in the mixed solution for 24 h to remove Co ions, taking it out, washing, and drying it to obtain the NC / CC precursor; (5) Ammonium molybdate tetrahydrate and thiourea are stirred and dissolved in water to obtain a mixed solution. The mixed solution and the NC / CC precursor obtained in step (4) are placed in a reactor for hydrothermal reaction. After the reaction is completed, the mixture is cooled to room temperature, the carbon cloth is taken out, washed, and dried to obtain a MoS2-loaded N-doped carbon multi-layer hydrogen evolution electrode material, which is recorded as Co-NC@MoS2 / CC; The constant temperature heat treatment in step (3) refers to heating to 700 ° C, constant temperature treatment at 700 ° C for 1 hour, and the heating rate is 2-3 ° C·min -1 ; The reaction temperature of the hydrothermal reaction in step (5) is 180°C, and the reaction time is 9-12 h.

2. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, wherein: The alcohol solution in step (1) is any one of 95% ethanol and isopropanol; The mass molar concentration of the potassium permanganate solution in step (1) is 0.5 M, and the soaking time is 1-2 h.

3. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, characterized in that: The molar ratio of 2-methylimidazole to cobalt nitrate hexahydrate in step (2) is 8:

1.

4. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, characterized in that: The constant temperature soaking in step (2) refers to soaking at 25°C for 6-8 hours.

5. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, characterized in that: The Ar gas flow in step (3) is 50 sccm; The acid solution in step (3) is a 1 M HCl solution; the immersion time is 12-24 h.

6. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, characterized in that: The mass molar concentration of the HCl solution in step (4) is 1M; the mass molar concentration of the FeCl3 solution is 3M; and the volume ratio of the HCl solution to the FeCl3 solution is 1:

100.

7. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, characterized in that: The molar ratio of ammonium molybdate tetrahydrate to thiourea in step (5) is 1:

15.

8. The method for preparing a MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material according to claim 1, characterized in that: The washing in steps (1) to (5) refers to rinsing with deionized water; the drying refers to drying at 50-80°C for 6-12 hours.

9. A MoS2-loaded N-doped carbon multi-level hydrogen evolution electrode material prepared according to the method according to any one of claims 1 to 8.

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