Biomass-based composite heterostructure hydrogen evolution catalyst and preparation method and application thereof

Abstract

The application provides a biomass-based composite heterostructure hydrogen evolution catalyst and a preparation method and application thereof, and belongs to the technical field of electrocatalytic decomposition hydrogen evolution catalysts. Biomass cellulose is prepared by treating biomass as raw material through a ternary eutectic solvent, cobalt is loaded on carbon cloth, a three-dimensional network Co@NCNT / CC carrier is prepared by combining microwave calcination, and the biomass-based composite heterostructure hydrogen evolution catalyst is prepared by preparing cobalt molybdate, and then carrying out a hydrothermal reaction on the cobalt molybdate, thiourea and the carrier. The catalyst takes Co@NCNT / CC as a three-dimensional carrier, grows petal-shaped CoS2@MoS2 heterojunction on the surface, and forms an efficient charge transport channel through Mo-S-Co bonds. The catalyst has excellent catalytic activity, reaction kinetics, structural stability and acid-base tolerance, the process is green and sustainable, and is suitable for industrial application of water electrolysis hydrogen production.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic hydrogen evolution catalyst technology, and in particular to a biomass-based composite heterostructure hydrogen evolution catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen, as a clean energy carrier with high energy density and zero carbon emissions, is crucial to the energy sector. Electrolysis of water has become an important method for hydrogen production due to its environmental friendliness and sustainability; however, the efficiency of the hydrogen evolution reaction is the core factor restricting the development of water electrolysis hydrogen production technology.

[0003] Currently, commercial hydrogen evolution catalysts are mainly platinum-based noble metals, which exhibit excellent catalytic performance in acidic environments. However, their high cost and scarcity of resources hinder large-scale industrial application. Molybdenum disulfide (MoS2), as a typical transition metal chalcogenide, possesses a layered crystal structure and abundant edge active sites, making it a highly promising non-noble metal hydrogen evolution catalyst. However, its poor conductivity, tendency to agglomerate, and poor stability in alkaline media limit its practical application.

[0004] To improve the performance of MoS2, researchers have employed strategies such as support engineering and heterojunction construction. However, current heterojunction catalysts often utilize single modification strategies, resulting in issues like poor heterojunction stability, insufficient understanding of interface enhancement mechanisms, and limited improvement in catalytic performance. Furthermore, the catalyst supports often lack sufficient conductivity and specific surface area to adequately disperse the active phase, leading to limited exposure of active sites and low charge transport efficiency. In addition, the raw materials for existing catalyst preparations are mostly chemically synthesized products, lacking green sustainability, further limiting their industrial application. Summary of the Invention

[0005] The purpose of this invention is to provide a biomass-based composite heterostructure hydrogen evolution catalyst, its preparation method and application, which solves the problems of high cost of existing platinum-based catalysts, poor conductivity, poor stability, low charge transport efficiency, poor acid and base adaptability and lack of green and sustainable raw materials. This catalyst can efficiently and stably evolve hydrogen under both acidic and alkaline conditions.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a biomass-based composite heterostructure hydrogen evolution catalyst, comprising the following steps: Biomass raw materials are mixed with a ternary eutectic solvent and extracted to obtain biomass cellulose; Carbon cloth is impregnated with a cobalt salt solution and loaded to obtain cobalt-loaded carbon cloth; The cobalt-loaded carbon cloth was calcined in the presence of biomass cellulose and melamine to obtain a cobalt-based nitrogen-doped carbon nanotube carrier. Cobalt source, molybdenum source and water are mixed and subjected to co-precipitation reaction, followed by annealing to obtain cobalt molybdate; The cobalt molybdate, thiourea, and water were mixed, and the resulting suspension was mixed with a cobalt-based nitrogen-doped carbon nanotube support. After hydrothermal treatment, the mixture was vacuum dried to obtain a biomass-based composite heterostructure hydrogen evolution catalyst.

[0007] Preferably, the biomass raw materials include walnut shell powder, palm shell powder, peanut shell powder, rice husk powder, or coconut shell powder; The ternary eutectic solvent is a mixture of ethylene glycol, choline chloride, and oxalic acid in a molar ratio of 1 to 3:1:1; The liquid-to-solid mass ratio of the ternary eutectic solvent to the biomass feedstock is 5~10:1; The extraction temperature is 60~120℃, the time is 1~3h, and the stirring speed is 300~600 rpm.

[0008] Preferably, the carbon cloth is pretreated before being immersed in the cobalt salt solution: the carbon cloth is treated at a constant temperature of 500~800℃ for 2~4 hours, then soaked in an acid solution, ultrasonically cleaned, and dried to obtain pretreated carbon cloth.

[0009] Preferably, the cobalt salt in the cobalt salt solution includes cobalt nitrate; the concentration of the cobalt salt solution is 0.2~0.6 g / L; and the loading time is 3~9 min.

[0010] Preferably, the cobalt-loaded carbon cloth, biomass cellulose, and melamine are placed in a microwave reactor and calcined. The internal spatial structure of the microwave reactor includes an upper layer, a middle layer, and a lower layer; the upper layer, the middle layer, and the lower layer are formed by glass frit cores; wherein, the upper layer is filled with cobalt-loaded carbon cloth, the middle layer is filled with melamine and biomass cellulose, the lower layer is provided with an air inlet, and the middle layer is provided with an air outlet. The microwave reactor is made of glass.

[0011] Preferably, the mass ratio of biomass cellulose to melamine is 1~5:10; The mass ratio of the cobalt-loaded carbon cloth to biomass cellulose is 1:0.5~1; The calcination temperature is 600~1000℃, the time is 2~5h, and the atmosphere is nitrogen.

[0012] Preferably, the cobalt source comprises cobalt nitrate hexahydrate; the molybdenum source comprises sodium molybdate dihydrate; The molar ratio of cobalt in the cobalt source to molybdenum in the molybdenum source is 0.5~2:1; The coprecipitation reaction was carried out at room temperature for 20-60 minutes. The annealing process is carried out at a temperature of 300~600℃ for 1~3 hours in a nitrogen atmosphere. The molar ratio of cobalt molybdate to thiourea is 0.5~2:10; The mass ratio of the cobalt-based nitrogen-doped carbon nanotube carrier to cobalt molybdate is 1:0.1~0.5; The hydrothermal treatment is performed at a temperature of 100~300℃ for a duration of 12~36h.

[0013] This invention provides a biomass-based composite heterostructure hydrogen evolution catalyst prepared by the preparation method described in the above technical solution.

[0014] Preferably, the biomass-based composite heterostructure hydrogen evolution catalyst comprises a cobalt-based nitrogen-doped carbon nanotube support and a CoS2@MoS2 heterojunction supported on the cobalt-based nitrogen-doped carbon nanotube support; In the biomass-based composite heterostructure hydrogen evolution catalyst, the content of Mo is 5-10%, the content of Co is 2-7%, the content of S is 15-20%, and the content of N is 20-25% by mass percentage.

[0015] This invention provides the application of the biomass-based composite heterostructure hydrogen evolution catalyst described in the above technical solution in hydrogen evolution through water electrolysis.

[0016] This invention provides a method for preparing a biomass-based composite heterostructure hydrogen evolution catalyst. The method uses biomass as raw material, first obtaining biomass cellulose through ternary eutectic solvent treatment, then supporting cobalt on carbon cloth and preparing a three-dimensional network Co@NCNT / CC support via microwave calcination; finally, preparing cobalt molybdate and reacting it with thiourea and the aforementioned support via hydrothermal reaction to obtain the biomass-based composite heterostructure hydrogen evolution catalyst. This catalyst uses Co@NCNT / CC as a three-dimensional support, enhancing overall conductivity. The petal-like CoS2@MoS2 heterojunctions grown on the surface have a larger specific surface area, fully exposing active sites, and the elements are uniformly distributed, preventing agglomeration. Furthermore, CoS2 and MoS2 form efficient charge transport channels through Mo-S-Co bonds, improving electron transfer rate and charge transport efficiency. Therefore, through a synergistic mechanism of "conductive network construction - interface electronic regulation - defect engineering optimization," the prepared catalyst possesses excellent catalytic activity, reaction kinetics, structural stability, and acid-base tolerance (chemical stability), solving the problems of poor stability, limited catalytic performance improvement, low active site exposure, and low charge transport efficiency of existing catalysts. The catalyst was used for hydrogen production by water electrolysis, and it achieved efficient hydrogen evolution in both 0.5M H2SO4 acidic system and 1M KOH alkaline system, with an overpotential decay rate of ≤40% after 50 hours of continuous reaction.

[0017] The process of this invention is green and sustainable, and is suitable for industrial applications of hydrogen production by water electrolysis. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the microwave reaction vessel in this invention; wherein, 1-air inlet, 2-air outlet, 3-glass core; Figure 2 Scanning electron microscope image of the Co@NCNT / CC carrier prepared in Example 1; Figure 3 Scanning electron microscope image of the CoS2@MoS2 / Co@NCNT / CC catalyst prepared in Example 1; Figure 4 Scanning electron microscope (SEM) image of the CoS2@MoS2 / Co@NCNT / CC catalyst prepared in Example 1 after continuous testing in acidic electrolyte (0.5M H2SO4) for 50 h; Figure 5 Scanning electron microscope image of the CoS2@MoS2 / Co@NCNT / CC catalyst prepared in Example 1 after continuous testing in alkaline electrolyte (1M KOH) for 50 h; Figure 6 The stability test diagram of the CoS2@MoS2 / Co@NCNT / CC catalyst prepared in Example 1 in acidic electrolyte (0.5M H2SO4) is shown in the inset, with the overpotential comparison before and after the reaction under acidic conditions. Figure 7 The image shows the stability test results of the CoS2@MoS2 / Co@NCNT / CC catalyst prepared in Example 1 in alkaline electrolyte (1M KOH). The inset shows the comparison of overpotential before and after the reaction under alkaline conditions. Figure 8 Tafel curves of the catalysts prepared in Example 1 and Comparative Examples 1-2 with the Co@NCNT / CC support in acidic electrolyte (0.5MH2SO4); Figure 9 Tafel curves of the catalysts prepared in Example 1 and Comparative Examples 1-2 with the Co@NCNT / CC support in alkaline electrolyte (1MKOH); Figure 10 Scanning electron microscope (SEM) image of the CoS2 / Co@NCNT / CC catalyst prepared for Comparative Example 1 after continuous testing in acidic electrolyte (0.5 M H2SO4) for 50 h; Figure 11 Scanning electron microscope (SEM) image of the MoS2 / Co@NCNT / CC catalyst prepared for Comparative Example 2 after 50 h of continuous testing in acidic electrolyte (0.5 M H2SO4). Detailed Implementation

[0019] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0020] This invention provides a method for preparing a biomass-based composite heterostructure hydrogen evolution catalyst, comprising the following steps: Biomass raw materials are mixed with a ternary eutectic solvent and extracted to obtain biomass cellulose; Carbon cloth is impregnated with a cobalt salt solution and loaded to obtain cobalt-loaded carbon cloth; The cobalt-loaded carbon cloth was calcined in the presence of biomass cellulose and melamine to obtain a cobalt-based nitrogen-doped carbon nanotube carrier. Cobalt source, molybdenum source and water are mixed and subjected to co-precipitation reaction, followed by annealing to obtain cobalt molybdate; The cobalt molybdate, thiourea, and water were mixed, and the resulting suspension was mixed with a cobalt-based nitrogen-doped carbon nanotube support. After hydrothermal treatment, the mixture was vacuum dried to obtain a biomass-based composite heterostructure hydrogen evolution catalyst.

[0021] The present invention preferably involves dissolving biomass raw materials in a ternary eutectic solvent for extraction.

[0022] In this invention, the biomass raw materials preferably include walnut shell powder, palm shell powder, peanut shell powder, rice husk powder, or coconut shell powder; the mesh size of the biomass raw materials is preferably 60-90 mesh, more preferably 70-80 mesh.

[0023] In this invention, the ternary eutectic solvent is preferably a mixture of ethylene glycol, choline chloride, and oxalic acid in a molar ratio of 1 to 3:1:1, and the molar ratio of ethylene glycol, choline chloride, and oxalic acid is more preferably 1 to 2:1:1. The ternary eutectic solvent is preferably prepared by mixing ethylene glycol, choline chloride, and oxalic acid in the above proportion and stirring at 80°C for 2 hours.

[0024] In this invention, the liquid-solid mass ratio of the ternary eutectic solvent to the biomass raw material is preferably 5~10:1, more preferably 6~8:1.

[0025] In this invention, the extraction temperature is preferably 60~120℃, more preferably 80~100℃; the extraction time is preferably 1~3h, more preferably 2h; and the stirring speed is preferably 300~600 rpm, more preferably 400~500 rpm.

[0026] After extraction, the present invention preferably involves sequential washing, filtration, and drying to obtain biomass cellulose. The present invention does not impose any particular limitations on the washing, filtration, and drying processes; any process well-known in the art can be followed.

[0027] The present invention involves immersing carbon cloth in a cobalt salt solution for loading, thereby obtaining cobalt-loaded carbon cloth.

[0028] The present invention does not impose any special limitations on the specifications and source of the carbon cloth, and any commercially available carbon cloth known in the art is acceptable; there are no limitations on the size of the carbon cloth, which can be adjusted according to the requirements, and more preferably 2×3cm.

[0029] In this invention, the carbon cloth is pretreated before being immersed in the cobalt salt solution: the carbon cloth is kept at a constant temperature of 500~800℃ (more preferably 600℃) for 2~4 hours, then soaked in an acid solution, ultrasonically cleaned, and dried to obtain pretreated carbon cloth; the acid solution is preferably a nitric acid solution, the concentration of the acid solution is preferably 3mol / L, and the soaking time in the acid solution is preferably 12 hours; the amount of acid solution used in this invention is preferably sufficient to completely impregnate the carbon cloth.

[0030] More preferably, the carbon is arranged in a crucible furnace and heated to a constant temperature at a rate of 5°C / min. After cooling, it is immersed in an acid solution, ultrasonically cleaned with anhydrous ethanol and deionized water for 15 min each, and then dried in a 60°C oven to obtain pretreated carbon cloth. This invention removes impurities from the surface of the carbon cloth through pretreatment, increasing its hydrophilicity and oxygen-containing functional groups.

[0031] In this invention, the cobalt salt in the cobalt salt solution preferably includes cobalt nitrate; the concentration of the cobalt salt solution is preferably 0.2~0.6 g / L, more preferably 0.4~0.5 g / L.

[0032] The present invention does not impose any special limitation on the ratio of carbon cloth to cobalt salt solution, as long as the carbon cloth is completely immersed in the cobalt salt solution.

[0033] In this invention, the loading time is preferably 3-9 minutes, more preferably 5-6 minutes. After loading, the material is vacuum dried at 60°C for 3 hours to obtain cobalt-loaded carbon cloth.

[0034] The present invention preferably places the cobalt-loaded carbon cloth, biomass cellulose and melamine in a microwave reactor.

[0035] In this invention, such as Figure 1 As shown, the internal spatial structure of the microwave reactor includes an upper layer, a middle layer, and a lower layer; the upper layer, the middle layer, and the lower layer are formed by glass frits; wherein, the upper layer is filled with cobalt-loaded carbon cloth, the middle layer is filled with melamine and biomass cellulose, the lower layer is provided with an air inlet, and the middle layer is provided with an air outlet. The microwave reactor is made of glass, more preferably quartz glass. The overall height of the microwave reactor is 192mm, the wall thickness is 1.5mm, and the bottom diameter is 50mm. The thickness of the glass frit core is 7mm, and the aperture is 250 mesh. The air inlet and outlet are frosted inlets with a diameter of 6mm.

[0036] The present invention does not have any particular limitation on the quartz glass and glass frit core, and any corresponding material well known in the art can be used.

[0037] In the microwave reactor described in this invention, the lower layer acts as an air intake buffer to prevent the powder in the middle layer from being blown away; the middle layer is the main heating zone, where melamine and biomass cellulose are rapidly pyrolyzed to produce high-temperature gas rich in C and N, which flows to the upper layer; carbon cloth is placed in the upper layer, and the C and N-containing gas from the middle layer comes into contact with the Co in the carbon cloth, initiating the growth of carbon nanotubes. This reactor structure is advantageous for obtaining the catalyst with the aforementioned structure and properties of this invention.

[0038] In this invention, the microwave reactor containing the reactants is preferably placed in a microwave pyrolysis experimental apparatus, and nitrogen gas is introduced for 15 minutes to remove oxygen (flow rate 30 mL / min) before calcination.

[0039] In this invention, the mass ratio of biomass cellulose to melamine is preferably 1~5:10, more preferably 2~3:10; the mass ratio of cobalt-loaded carbon cloth to biomass cellulose is 1:0.5~1, more preferably 1:1.

[0040] In this invention, the calcination temperature is preferably 600~1000℃, more preferably 800~900℃, the calcination time is preferably 2~5h, more preferably 2~3h; the atmosphere is preferably nitrogen; and the heating rate to the calcination temperature is preferably 5℃ / min.

[0041] After calcination, the present invention preferably cools the product to room temperature at 5℃ / min, washes the product, and dries it to obtain a cobalt-based nitrogen-doped carbon nanotube carrier, denoted as Co@NCNT / CC.

[0042] In this invention, the preferred method for preparing cobalt molybdate is as follows: cobalt source, molybdenum source and water are mixed, co-precipitated, filtered and dried, and the resulting precipitate is annealed to obtain cobalt molybdate.

[0043] In this invention, the cobalt source preferably includes cobalt nitrate hexahydrate; the molybdenum source preferably includes sodium molybdate dihydrate; the molar ratio of cobalt in the cobalt source to molybdenum in the molybdenum source is preferably 0.5~2:1, more preferably 1~1.5:1.

[0044] This invention does not impose any special limitation on the amount of water used in the preparation of cobalt molybdate, as long as the materials are thoroughly mixed; in the embodiments, the ratio of cobalt molybdate to water is specifically 0.5 mmol: 20 mL.

[0045] In this invention, the temperature of the coprecipitation reaction is preferably room temperature, the stirring speed is preferably 600 rpm, and the time is preferably 20-60 min, more preferably 40-50 min.

[0046] In this invention, the annealing temperature is preferably 300~600℃, more preferably 400~500℃; the time is preferably 1~3h, more preferably 1.5~2h; the atmosphere is nitrogen; and the heating rate to the annealing temperature is preferably 5℃ / min.

[0047] This invention provides cobalt molybdate prepared by room temperature co-precipitation, vacuum filtration and drying, and nitrogen atmosphere annealing. By precisely controlling the cobalt-molybdenum molar ratio and annealing temperature and time, it meets the requirements for constructing CoS2@MoS2 heterojunction catalysts. This avoids the problems of complex preparation processes, incompatible procedures, and non-reproducible experimental results caused by the use of commercially available cobalt molybdate due to differences in raw material composition and batches, thus ensuring the successful construction and performance stability of CoS2@MoS2 heterojunction catalysts.

[0048] In this invention, the molar ratio of cobalt molybdate to thiourea is preferably 0.5~2:10, more preferably 0.5~1:10; the mass ratio of the cobalt-based nitrogen-doped carbon nanotube carrier to cobalt molybdate is preferably 1:0.1~0.5, more preferably 1:0.2~0.3.

[0049] In this invention, cobalt molybdate and thiourea are preferably dispersed in deionized water and ultrasonically dispersed for 15-30 minutes to form a uniform suspension. The resulting suspension and cobalt-based nitrogen-doped carbon nanotube carrier are placed together in a stainless steel autoclave lined with polytetrafluoroethylene. After sealing, the autoclave is placed in an oven for hydrothermal treatment.

[0050] In this invention, the temperature of the hydrothermal treatment is preferably 100~300℃, more preferably 200~250℃, and the time is preferably 12~36h, more preferably 24h.

[0051] After completing the hydrothermal treatment, the present invention preferably cools the obtained product naturally to room temperature, washes it several times alternately with deionized water and anhydrous ethanol, and then vacuum dries it at 50~80℃ (more preferably 60~70℃) for 9h to obtain a biomass-based composite heterostructure hydrogen evolution catalyst, denoted as CoS2@MoS2 / Co@NCNT / CC.

[0052] This invention provides a biomass-based composite heterostructure hydrogen evolution catalyst prepared by the preparation method described in the above technical solution.

[0053] In this invention, the biomass-based composite heterostructure hydrogen evolution catalyst includes a cobalt-based nitrogen-doped carbon nanotube support (Co@NCNT / CC) and a CoS2@MoS2 heterojunction supported on the cobalt-based nitrogen-doped carbon nanotube support; wherein, Co@NCNT is a curved fibrous structure forming a three-dimensional network support, and the CoS2@MoS2 heterojunction has a petal-like stacked morphology.

[0054] In this invention, the biomass-based composite heterostructure hydrogen evolution catalyst contains, by mass percentage, 5-10% Mo, 2-7% Co, 15-20% S, and 20-25% N, with each element uniformly distributed in the catalyst. More preferably, the Mo content is 8.39-9.7%, the Co content is 2.18-4.09%, the S content is 18.17-18.97%, and the N content is 23.63-24.39%.

[0055] The biomass-based composite heterostructure hydrogen evolution catalyst prepared by this invention uses carbon cloth as a substrate, on which cobalt-based nitrogen-doped carbon nanotubes are grown in situ to form a three-dimensional network Co@NCNT / CC support. On the surface and gaps of the support, petal-shaped stacked CoS2@MoS2 heterojunctions are densely grown as catalytic active centers. CoS2 and MoS2 achieve atomic-level contact through Mo-S-Co bonds, forming a highly efficient cross-phase charge transport channel.

[0056] This invention provides the application of the biomass-based composite heterostructure hydrogen evolution catalyst described in the above technical solution in hydrogen evolution through water electrolysis.

[0057] The biomass-based composite heterostructure hydrogen evolution catalyst is used as the working electrode in the electrolysis of water for hydrogen evolution reaction in an acidic or alkaline electrolyte system; the acidic electrolyte is preferably a 0.3-0.7M sulfuric acid solution, more preferably a 0.5M H2SO4 solution; the alkaline electrolyte is preferably a 0.8-1.2M potassium hydroxide solution, more preferably a 1M KOH solution.

[0058] This invention does not impose any special limitations on the specific methods and conditions for the application; it can be applied in accordance with methods well known in the art.

[0059] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0060] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0061] Example 1

[0062] S1. Add 80-mesh walnut shell powder to a ternary eutectic solvent at a liquid-to-solid ratio of 8:1 g / g. The ternary eutectic solvent is prepared by mixing ethylene glycol, choline chloride, and oxalic acid in a 1:1:1 molar ratio and stirring at 80°C for 2 hours. Place the mixture in a heat-collecting constant-temperature magnetic stirrer and stir at 120°C and 400 rpm for 2 hours. After the reaction, wash the mixture alternately with deionized water and anhydrous ethanol until the filtrate is neutral. After filtration, dry the filtrate at 80°C for 8 hours to obtain walnut shell cellulose powder.

[0063] S2. Take a 2×3cm carbon cloth (carbon energy carbon cloth WOS1011) and place it in a crucible furnace. Heat it to 600℃ at 5℃ / min and hold it at that temperature for 4 hours. After cooling, immerse it in a 3mol / L nitric acid solution for 12 hours. Clean it with anhydrous ethanol and deionized water for 15 minutes each. Dry it in a 60℃ oven to obtain pretreated carbon cloth. Immerse the pretreated carbon cloth in a 0.4g / L cobalt nitrate hexahydrate solution for 6 minutes. After removing it, vacuum dry it at 60℃ for 3 hours to obtain cobalt-loaded carbon cloth.

[0064] S3. According to Figure 1 The microwave reactor is constructed as shown, wherein the microwave reactor is made of quartz glass, with an overall height of 192 mm, a wall thickness of 1.5 mm, and a bottom diameter of 50 mm; the glass frit core has a thickness of 7 mm and a pore size of 250 mesh; the air inlet and outlet are frosted inlets with a diameter of 6 mm. Cobalt-loaded carbon was placed in the upper layer of the microwave reactor. Walnut shell cellulose powder and melamine were added to the middle layer at a mass ratio of 3:10, and the mass ratio of cobalt-loaded carbon cloth to walnut shell cellulose powder was 1:1. The reactor was placed in a microwave pyrolysis experimental device, and nitrogen gas was introduced for 15 minutes to remove oxygen (flow rate 30 mL / min). The temperature was increased to 800℃ at 5℃ / min under nitrogen atmosphere and calcined for 2 hours. Then the temperature was reduced to room temperature at 5℃ / min. After removal, the filtrate was rinsed with deionized water until neutral and dried at 60℃ to obtain the Co@NCNT / CC carrier.

[0065] S4. Cobalt nitrate hexahydrate and sodium molybdate dihydrate were dissolved in 50 mL of deionized water at a molar ratio of cobalt:molybdenum = 1:1. The mixture was stirred vigorously at 600 rpm for 40 minutes at room temperature to obtain a precipitate. After filtration and drying, the precipitate was placed in a tube furnace and heated to 500 °C at 5 °C / min. The precipitate was then annealed under a nitrogen atmosphere for 2 hours to obtain cobalt molybdate.

[0066] S5. 0.5 mmol (0.1 g) of cobalt molybdate and 10 mmol of thiourea were dispersed in 20 mL of deionized water and ultrasonically dispersed for 30 min to form a uniform suspension. The resulting suspension and 1 g of Co@NCNT / CC support were placed in a stainless steel autoclave lined with polytetrafluoroethylene. After sealing, the autoclave was placed in an oven and hydrothermally treated at 200 °C for 24 h. After naturally cooling to room temperature, the autoclave was rinsed 4 times alternately with deionized water and anhydrous ethanol and vacuum dried at 60 °C for 9 h to obtain a biomass-based composite heterostructure hydrogen evolution catalyst, denoted as CoS2@MoS2 / Co@NCNT / CC. In this catalyst, the content of Mo element is 9.7%, the content of Co element is 4.09%, the content of S element is 18.17%, and the content of N element is 24.39% by mass percentage.

[0067] Example 2

[0068] The only difference from Example 1 is: In step S1, the liquid-to-solid ratio is 5:1 g / g, and the reaction conditions are 60℃, stirring at 300 rpm for 3 hours; In step S3, the mass ratio of walnut shell cellulose powder to melamine is 1:10, and the calcination temperature is 600℃. In step S4, the cobalt:molybdenum molar ratio is 0.5:1, the annealing temperature is 300℃, and the annealing time is 1h. In step S5, the hydrothermal temperature is 250℃, and the rest is the same as in Example 1. In the prepared biomass-based composite heterostructure hydrogen evolution catalyst, the content of Mo is 9.36%, the content of Co is 2.18%, the content of S is 18.97%, and the content of N is 24.7% by mass percentage.

[0069] Example 3

[0070] The only difference from Example 1 is: In step S1, the biomass is 80-mesh palm shell powder, the liquid-to-solid ratio is 10:1 g / g, and the reaction conditions are 120℃, 600 rpm stirring for 1 hour; In step S3, the mass ratio of palm shell cellulose powder to melamine is 5:10, and the calcination temperature is 1000℃. In step S4, the cobalt:molybdenum molar ratio is 2:1, the annealing temperature is 600℃, and the annealing time is 3h. In step S5, the hydrothermal temperature is 300℃, and the rest is the same as in Example 1. In the prepared biomass-based composite heterostructure hydrogen evolution catalyst, the content of Mo is 8.39%, the content of Co is 6.91%, the content of S is 18.29%, and the content of N is 23.63% by mass percentage.

[0071] Comparative Example 1

[0072] The only difference from Example 1 is that in step S5, 0.5 mmol cobalt molybdate is replaced with 1 mmol cobalt nitrate. All other preparation steps and process parameters are completely consistent with Example 1, resulting in CoS2 / Co@NCNT / CC.

[0073] Comparative Example 2

[0074] The only difference from Example 1 is that in step S5, 0.5 mmol cobalt molybdate is replaced with 1 mmol sodium molybdate. All other preparation steps and process parameters are completely consistent with Example 1, resulting in MoS2 / Co@NCNT / CC.

[0075] Characterization and performance testing

[0076] 1) Figure 2 Scanning electron microscope image of the Co@NCNT / CC carrier prepared in Example 1; by Figure 2 It can be seen that the nitrogen-doped carbon nanotubes uniformly grown on the surface of carbon cloth (CC) exhibit a typical curved fibrous morphology. The three-dimensional interwoven network of carbon nanotubes provides high conductivity, making it an ideal carrier for CoS2@MoS2 loading.

[0077] 2) Figure 3 Scanning electron microscope (SEM) image of the CoS2@MoS2 / Co@NCNT / CC catalyst prepared in Example 1; Figure 3 It can be seen that the surface of this composite material exhibits a significant uneven and wrinkled morphology. This morphology originates from the random self-assembly of MoS2 nanosheets and the synergistic growth of CoS2 and MoS2. MoS2 is grown in situ on the surface of Co@NCNT by hydrothermal method. The interlayer van der Waals forces induce the nanosheets to stack along different orientations, forming a "petal-like" secondary structure.

[0078] 3) The hydrogen evolution performance of the CoS2@MoS2 / Co@NCNT / CC catalysts prepared in Examples 1-3 and the catalysts in Comparative Examples 1-2 was tested using a three-electrode system. The prepared catalyst was used as the working electrode, and a platinum mesh was used as the counter electrode. Ag / AgCl was used as the reference electrode under acidic conditions, and Hg / HgO was used as the reference electrode under alkaline conditions. The test results are shown in Table 1 and... Figures 4-11 : Table 1 Performance data of Examples 1-3 and Comparative Examples 1-2

[0079] From Table 1 and Figures 4-11 It can be known that: The catalysts in Examples 1-3 of this invention exhibited an overpotential decay rate ≤40% after 50 hours of continuous hydrogen evolution reaction. Figure 6 and Figure 7 ), far lower than comparative examples 1-2, and combined Figure 4 and Figure 5 The SEM images show that the catalyst in Example 1 has a complete microstructure, with no obvious active phase aggregates or metal dissolution, exhibiting good stability and acid-base tolerance.

[0080] The CoS2@MoS2 / Co@NCNT / CC composite heterojunction catalysts prepared in Examples 1-3 of this invention exhibit excellent hydrogen evolution performance in both acidic and alkaline electrolytes, with a performance of 10 mA / cm². 2 The overpotentials at current densities were both below 95 mV and 145 mV, respectively, which were significantly lower than those of the CoS2 single-component catalyst in Comparative Example 1 and the MoS2 single-component catalyst in Comparative Example 2, and the Tafel slope was also smaller. Figure 8 and Figure 9 This indicates that the hydrogen evolution reaction kinetics are superior.

[0081] After stability testing under acidic conditions (0.5M H2SO4), samples from comparative examples 1 and 2 showed varying degrees of active phase aggregation and dissolution. Figure 10 and Figure 11 This demonstrates that the CoS2@MoS2 heterojunction constructed in this invention can significantly improve the structural stability and acid-base tolerance of the catalyst.

[0082] As can be seen from the comparison of Examples 1 and 2, single CoS2 or MoS2-based catalysts have performance shortcomings in acidic or alkaline systems. However, this invention achieves synergistic enhancement of the two active components by constructing a CoS2@MoS2 heterojunction, taking into account the hydrogen evolution efficiency in both acidic and alkaline systems, and solving the technical defect of poor acid-base adaptability of traditional single-component non-precious metal catalysts.

[0083] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a biomass-based composite heterostructure hydrogen evolution catalyst, characterized in that, Includes the following steps: Biomass raw materials are mixed with a ternary eutectic solvent and extracted to obtain biomass cellulose; Carbon cloth is impregnated with a cobalt salt solution and loaded to obtain cobalt-loaded carbon cloth; The cobalt-loaded carbon cloth was calcined in the presence of biomass cellulose and melamine to obtain a cobalt-based nitrogen-doped carbon nanotube carrier. Cobalt source, molybdenum source and water are mixed and subjected to co-precipitation reaction, followed by annealing to obtain cobalt molybdate; The cobalt molybdate, thiourea, and water were mixed, and the resulting suspension was mixed with a cobalt-based nitrogen-doped carbon nanotube support. After hydrothermal treatment, the mixture was vacuum dried to obtain a biomass-based composite heterostructure hydrogen evolution catalyst.

2. The preparation method according to claim 1, characterized in that, The biomass raw materials include walnut shell powder, palm shell powder, peanut shell powder, rice husk powder, or coconut shell powder; The ternary eutectic solvent is a mixture of ethylene glycol, choline chloride, and oxalic acid in a molar ratio of 1 to 3:1:1; The liquid-to-solid mass ratio of the ternary eutectic solvent to the biomass feedstock is 5~10:1; The extraction temperature is 60~120℃, the time is 1~3h, and the stirring speed is 300~600 rpm.

3. The preparation method according to claim 1, characterized in that, Before immersing the carbon cloth in the cobalt salt solution, the carbon cloth is pretreated: after being treated at a constant temperature of 500~800℃ for 2~4 hours, the carbon cloth is soaked in an acid solution, ultrasonically cleaned, and then dried to obtain pretreated carbon cloth.

4. The preparation method according to claim 1, characterized in that, The cobalt salt in the cobalt salt solution includes cobalt nitrate; the concentration of the cobalt salt solution is 0.2~0.6 g / L; and the loading time is 3~9 min.

5. The preparation method according to claim 1, characterized in that, The cobalt-loaded carbon cloth, biomass cellulose, and melamine were placed in a microwave reactor and calcined. The internal spatial structure of the microwave reactor includes an upper layer, a middle layer, and a lower layer; the upper layer, the middle layer, and the lower layer are formed by glass frit cores; wherein, the upper layer is filled with cobalt-loaded carbon cloth, the middle layer is filled with melamine and biomass cellulose, the lower layer is provided with an air inlet, and the middle layer is provided with an air outlet. The microwave reactor is made of glass.

6. The preparation method according to claim 1 or 5, characterized in that, The mass ratio of biomass cellulose to melamine is 1~5:10; The mass ratio of the cobalt-loaded carbon cloth to biomass cellulose is 1:0.5~1; The calcination temperature is 600~1000℃, the time is 2~5h, and the atmosphere is nitrogen.

7. The preparation method according to claim 1, characterized in that, The cobalt source includes cobalt nitrate hexahydrate; the molybdenum source includes sodium molybdate dihydrate; The molar ratio of cobalt in the cobalt source to molybdenum in the molybdenum source is 0.5~2:1; The coprecipitation reaction was carried out at room temperature for 20-60 minutes. The annealing process is carried out at a temperature of 300~600℃ for 1~3 hours in a nitrogen atmosphere. The molar ratio of cobalt molybdate to thiourea is 0.5~2:10; The mass ratio of the cobalt-based nitrogen-doped carbon nanotube carrier to cobalt molybdate is 1:0.1~0.5; The hydrothermal treatment is performed at a temperature of 100~300℃ for a duration of 12~36h.

8. The biomass-based composite heterostructure hydrogen evolution catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. The biomass-based composite heterostructure hydrogen evolution catalyst according to claim 8, characterized in that, The biomass-based composite heterostructure hydrogen evolution catalyst includes a cobalt-based nitrogen-doped carbon nanotube support and a CoS2@MoS2 heterojunction supported on the cobalt-based nitrogen-doped carbon nanotube support. In the biomass-based composite heterostructure hydrogen evolution catalyst, the content of Mo is 5-10%, the content of Co is 2-7%, the content of S is 15-20%, and the content of N is 20-25% by mass percentage.

10. The application of the biomass-based composite heterostructure hydrogen evolution catalyst according to claim 8 or 9 in hydrogen evolution through water electrolysis.

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