Preparation method and application of jute-derived porous carbon material loaded with molybdenum carbide

Abstract

The invention provides a preparation method and application of a jute-derived porous carbon material loaded with molybdenum carbide, and belongs to the technical field of electrochemical catalysis. The preparation method comprises the following steps: pretreating jute fibers to obtain jute powder; jute powder is placed in the molybdenum-containing compound solution, a mixture is obtained, the jute powder in the mixture adsorbs a molybdenum-containing compound, and the mass ratio of the jute powder to the molybdenum-containing compound in the molybdenum-containing compound solution is any one of 1: (2.5-6.25); and carrying out carbonization treatment on the jute powder adsorbed with the molybdenum-containing compound at 800-900 DEG C to obtain the jute derived porous carbon material loaded with molybdenum carbide. The jute fiber-derived porous carbon is adopted as a carrier, full adsorption and combination of a precursor are achieved in a molybdenum-containing compound solution, high dispersion and stable loading of molybdenum carbide are achieved by regulating and controlling the mass ratio and the carbonization temperature, and the structural stability and catalytic activity of the molybdenum carbide-based catalyst are improved; the catalytic efficiency of the hydrogen evolution reaction is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical catalysis, and in particular to a preparation method and application of a molybdenum carbide-loaded jute fiber-derived porous carbon material. BACKGROUND

[0002] Hydrogen energy is considered to be a promising clean energy alternative due to its high energy density and zero emission characteristics. Water electrolysis is one of the common methods for hydrogen production, but it generally relies on platinum-based catalysts to achieve high electrocatalytic efficiency in practical applications. Such catalysts are expensive, and the water electrolysis process usually requires high energy input.

[0003] To reduce costs and improve catalytic performance, researchers have proposed using transition metal-based catalysts to replace platinum-based catalysts. Transition metal-based catalysts are of interest due to their similar electronic structure (e.g., d-band characteristics) to noble metals, high cost-effectiveness, and adjustable reactivity to hydrogen intermediates. Among them, molybdenum carbide exhibits excellent catalytic activity in the hydrogen evolution reaction due to its close-to-optimal hydrogen adsorption free energy, good corrosion resistance, and long service life. However, molybdenum carbide has low intrinsic electronic conductivity, and is prone to particle agglomeration during the reaction, which hinders electron transport and reduces the number of effective active sites, thereby reducing the overall catalytic efficiency.

[0004] Existing technologies usually composite molybdenum carbide with conductive porous materials to utilize the high specific surface area and conductivity of the conductive porous materials to alleviate the agglomeration of molybdenum carbide and improve its conductivity. However, such composite catalysts still have the following technical defects: (1) the mechanical stability of the porous carbon material is insufficient, and the structure collapses easily during the high-temperature loading of molybdenum carbide, resulting in a decrease in the overall structural stability of the catalyst. (2) During high-temperature treatment, the porous carbon material is prone to graphitization, which changes its surface chemical properties and reduces the interfacial bonding force with molybdenum carbide. (3) Molybdenum carbide is prone to phase transformation or chemical reaction with the carbon skeleton under high-temperature conditions, resulting in unstable crystal phase and loss of active sites, which in turn reduces the catalytic activity and service life. Therefore, there is an urgent need to provide a preparation method for a porous carbon-based carrier that can maintain structural stability under high-temperature conditions, effectively inhibit the agglomeration of molybdenum carbide particles, and have excellent conductivity, in order to achieve efficient utilization of molybdenum carbide active sites and improve the catalytic efficiency of the hydrogen evolution reaction. SUMMARY

[0005] To solve the above problems, according to the first aspect of the present application, a preparation method of a molybdenum carbide-loaded jute fiber-derived porous carbon material is provided, comprising the following steps: pretreating jute fibers to obtain jute powder; placing the jute powder in a molybdenum-containing compound solution to obtain a mixture, wherein the jute powder in the mixture is adsorbed with the molybdenum-containing compound, and a mass ratio of the jute powder to the molybdenum-containing compound in the molybdenum-containing compound solution is any value in the range of 1:(2.5-6.25); The jute powder adsorbed with the molybdenum-containing compound is carbonized at 800° C.-900° C. to obtain a jute-derived porous carbon material loaded with molybdenum carbide.

[0006] Optionally, the carbonization treatment of the jute powder adsorbed with the molybdenum-containing compound at 800° C.-900° C. to obtain the jute-derived porous carbon material loaded with molybdenum carbide comprises the following steps: The jute powder adsorbed with the molybdenum-containing compound is heated from room temperature to 300-400° C. at a heating rate of 8-10° C. / min and kept at this temperature for 20-30 minutes; Then, increase the temperature from 300-400°C to 600-700°C at a heating rate of 3-5°C / min and keep it at that temperature for 20-30 minutes. Then, the temperature is increased from 600°C-700°C to 800°C-900°C at a heating rate of 2°C / min-5°C / min, and kept at this temperature for 90min-150min.

[0007] Optionally, the step of carbonizing the jute powder adsorbed with the molybdenum-containing compound at 800° C. to 900° C. to obtain the jute-derived porous carbon material loaded with molybdenum carbide further comprises pretreatment before the carbonization treatment; In the pretreatment step, the jute powder adsorbed with the molybdenum-containing compound is reacted with a polyamine nitrogen source compound solution at 60° C.-100° C. for 1 h-4 h to obtain an intermediate product.

[0008] Optionally, the polyamine nitrogen source compound is selected from a combination of one or more of ethylenediamine, diethylenetriamine and triethylenetetramine; The mass ratio of the polyamine nitrogen source compound to the jute powder is any value between (0.5-2):1.

[0009] Optionally, in the step of taking out the jute powder adsorbed with the molybdenum-containing compound and drying it, and then carbonizing it to obtain a jute-derived porous carbon material loaded with molybdenum carbide, the carbonization time is any value between 1.5h and 2.5h, and the carbonization heating rate is any value between 2°C / min and 10°C / min.

[0010] Optionally, the solute in the molybdenum compound solution is selected from a combination of one or more of ammonium molybdate tetrahydrate, sodium molybdate and potassium molybdate.

[0011] Optionally, the particle size of the molybdenum carbide in the jute-derived porous carbon material loaded with molybdenum carbide is any value between 20 nm and 60 nm.

[0012] Optionally, in the step of pretreating the jute fiber to obtain jute powder, the specific steps of the pretreatment are: washing and drying the jute fibers to obtain treated jute fibers; The treated jute fibers are crushed and sieved to obtain jute powder.

[0013] According to a second aspect of the present application, a catalyst containing molybdenum carbide is provided, which is prepared by the aforementioned preparation method.

[0014] According to a third aspect of the present application, there is provided a use of the aforementioned catalyst containing molybdenum carbide, wherein the catalyst containing molybdenum carbide is used as a catalytic material for an electric cathode and for a hydrogen evolution reaction.

[0015] According to the solution of the present invention, jute fiber-derived porous carbon is used as a carrier, and sufficient adsorption and bonding of the precursor is achieved in a molybdenum compound solution. By precisely controlling the mass ratio and carbonization temperature, molybdenum carbide can be highly dispersed and stably loaded on the porous carbon skeleton. In addition, by combining the spatial confinement effect of the porous carbon skeleton with excellent mechanical robustness, the migration and structural degradation of molybdenum carbide particles under electrochemical service conditions are effectively suppressed. The present invention utilizes the natural multi-level pore structure and high carbon content of jute fiber to construct a conductive carbon-based skeleton with rich pores during the carbonization process, thereby significantly improving the specific surface area and electron transfer efficiency of the material. At the same time, by precisely controlling the carbonization temperature range and heating rate, the agglomeration and phase change of molybdenum carbide particles at high temperatures are suppressed, and the crystal phase stability and interfacial bonding strength with the carbon-based carrier are enhanced. As a result, the present invention can significantly improve the structural stability and catalytic activity of molybdenum carbide-based catalysts, and further improve the catalytic efficiency of hydrogen evolution reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram showing a method for preparing a jute-derived porous carbon material loaded with molybdenum carbide according to one embodiment of the present invention; Figure 2 shows an SEM image of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention; Figure 3 shows an SEM image of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Comparative Example 1 of the present invention; Figure 4 shows an EDS image of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention; Figure 5A TEM image of the molybdenum carbide supported jute-derived porous carbon material prepared in Example 1 of the present application is shown; Figure 6 A HR-TEM image of the molybdenum carbide supported jute-derived porous carbon material prepared in Example 1 of the present application is shown; Figure 7 A XRD image of the molybdenum carbide supported jute-derived porous carbon material prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present application is shown; Figure 8 A catalyst polarization curve of the molybdenum carbide supported jute-derived porous carbon material prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present application is shown; Figure 9 A Tafel curve of the molybdenum carbide supported jute-derived porous carbon material prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present application is shown; Figure 10 A long-term stability plot of the molybdenum carbide supported jute-derived porous carbon material prepared in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0017] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the purpose of description, only the parts related to the present application are shown in the drawings, rather than all the structures. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0018] The terms "comprising" and "having" and any variations thereof in the present application are intended to cover the inclusions without limitation. For example, a process, method, system, product or apparatus including a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or apparatus.

[0019] Reference to "embodiment" in this document means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The various technical features of the embodiments described above can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0020] Figure 1 Schematic diagram showing a method for preparing a jute-derived porous carbon material loaded with molybdenum carbide according to one embodiment of the present invention. Figure 1 As shown, the preparation method comprises the following steps: S1, pretreating jute fibers to obtain jute powder.

[0021] S2, placing jute powder in a molybdenum-containing compound solution to obtain a mixture, wherein the jute powder in the mixture is adsorbed with the molybdenum-containing compound, and the mass ratio of the jute powder to the molybdenum-containing compound in the molybdenum-containing compound solution is 1:(2.5-6.25) or any value.

[0022] S3, carbonizing the jute powder adsorbed with the molybdenum-containing compound at 800° C.-900° C. to obtain a jute-derived porous carbon material loaded with molybdenum carbide.

[0023] According to the solution of the present invention, jute fiber-derived porous carbon is used as a carrier, and sufficient adsorption and bonding of the precursor is achieved in a molybdenum compound solution. By precisely controlling the mass ratio and carbonization temperature, molybdenum carbide can be highly dispersed and stably loaded on the porous carbon skeleton. In addition, by combining the spatial confinement effect of the porous carbon skeleton with excellent mechanical robustness, the migration and structural degradation of molybdenum carbide particles under electrochemical service conditions are effectively suppressed. The present invention utilizes the natural multi-level pore structure and high carbon content of jute fiber to construct a conductive carbon-based skeleton with rich pores during the carbonization process, thereby significantly improving the specific surface area and electron transfer efficiency of the material. At the same time, by precisely controlling the carbonization temperature range, the agglomeration and phase change of molybdenum carbide particles at high temperatures are suppressed, and the crystal phase stability and the interfacial bonding strength with the carbon-based carrier are enhanced. As a result, the present invention can significantly improve the structural stability and catalytic activity of molybdenum carbide-based catalysts, and further improve the catalytic efficiency of the hydrogen evolution reaction.

[0024] In step S1, jute fiber is pretreated to remove surface impurities and moisture and to homogenize its structure, thereby obtaining jute powder of suitable particle size and purity for subsequent efficient adsorption of molybdenum-containing compounds. In one embodiment, the specific steps of the pretreatment are: S101, washing and drying the jute fibers to obtain treated jute fibers.

[0025] S102, crushing and sieving the treated jute fibers to obtain jute powder.

[0026] In step S101, jute fibers are ultrasonically cleaned in ethanol and deionized water for 1-2 hours, for example, 1 hour, 1.5 hours, or 2 hours, to remove impurities. The cleaned jute fibers are then dried to obtain treated jute fibers.

[0027] In step S102, the pulverization process is performed at a rotation speed of 25,000 rpm to 32,000 rpm, for example, 25,000 rpm, 28,500 rpm, or 32,000 rpm. The pulverization time is 25 min to 35 min, for example, 25 min, 30 min, or 35 min. The sieve used for sieving is a 120-mesh sieve or a 150-mesh sieve. The pulverization and sieving process under these conditions yields jute powder with uniform particle size and good dispersibility, thereby increasing its specific surface area and surface active sites, and improving its contact and adsorption efficiency with the molybdenum-containing compound solution.

[0028] In step S2, the solute in the molybdenum-containing compound solution is selected from one or more combinations of ammonium molybdate tetrahydrate, sodium molybdate and potassium molybdate. The solvent in the molybdenum-containing compound solution is deionized water. The molybdenum-containing compound solution is used to provide a precursor ion source for molybdenum carbide, so that the molybdenum element can be uniformly adsorbed and anchored on the surface of jute powder, laying the foundation for the formation of nano-scale molybdenum carbide particles in the subsequent carbonization process. In one embodiment, the mass ratio of the molybdenum-containing compound in the jute powder and the molybdenum-containing compound solution is 1: (2.5-6.25) in any value, for example, it can be 1:2.5, 1:3, 1:3.5, 1:4.375, 1:4.5, 1:5, 1:5.5 or 1:6.25, or it can be 1: (2.5-6.25) in any value. When the mass ratio is greater than 1:6.25, it is easy to cause molybdenum carbide particles to agglomerate, increase particle size and reduce active sites. And when the mass ratio is less than 1:2.5, it will cause insufficient molybdenum content and reduced catalytic activity. In one embodiment, jute powder is immersed in a molybdenum compound solution for 10 h to 14 h, for example, 10 h, 12 h, or 14 h, to achieve adsorption equilibrium, so that the molybdenum compound is fully combined and evenly distributed on the surface of the jute powder, thereby ensuring the uniformity of the particle size and distribution of molybdenum carbide in the subsequent carbonization process.

[0029] In step S3, the carbonization treatment adopts a staged temperature rising carbonization, including the following steps: S301, the jute powder adsorbed with the molybdenum-containing compound is heated from room temperature to 300-400℃ at a heating rate of 8-10℃ / min, and is kept for 20-30min.

[0030] S302, then heated from 300-400℃ to 600-700℃ at a heating rate of 3-5℃ / min, and is kept for 20-30min.

[0031] S303, then heated from 600-700℃ to 800-900℃ at a heating rate of 2-5℃ / min, and is kept for 90-150min.

[0032] In step S301, the heating rate is any value in the range of 8-10℃ / min, for example, it can be 8℃ / min, 9℃ / min or 10℃ / min. The heating temperature is from room temperature to 300-400℃, for example, it can be 300℃, 320℃, 340℃, 350℃, 360℃, 380℃ or 400℃. The keeping time is any value in the range of 20-30min, for example, it can be 20min, 22min, 24min, 25min, 26min, 28min or 30min. Through the low-temperature preheating stage, the residual water and low-molecular organic matter in the jute powder are removed, avoiding the collapse of the pore structure due to volatilization in the subsequent high-temperature carbonization process.

[0033] In step S302, the heating rate is any value in the range of 3-5℃ / min, for example, it can be 3℃ / min, 4℃ / min or 5℃ / min. The heating temperature is from 300-400℃ to 600-700℃, for example, it can be 600℃, 620℃, 640℃, 650℃, 660℃, 680℃ or 700℃. The keeping time is any value in the range of 20-30min, for example, it can be 20min, 22min, 24min, 25min, 26min, 28min or 30min. Through the medium-temperature stage, the preliminary solid-phase reaction of the molybdenum-containing compound with the carbon-based skeleton is induced, and the gradual stabilization of the carbon skeleton structure is promoted.

[0034] In step S303, the heating rate is any value between 2°C / min and 5°C / min, for example, 2°C / min, 3°C / min, 4°C / min or 5°C / min. The heating temperature is from 600°C-700°C to 800°C-900°C, for example, 800°C, 820°C, 840°C, 850°C, 860°C, 880°C or 900°C. The holding time is any value between 90min and 150min, for example, 90min, 100min, 110min, 120min, 130min, 140min or 150min. The carbonization reaction of the molybdenum-containing compound is completed in the high temperature stage to generate molybdenum carbide particles with stable crystal phase and highly dispersed, while maintaining the porous structural integrity of the carbon-based skeleton.

[0035] Through the above-mentioned high-temperature carbonization treatment with staged heating, molybdenum carbide is highly dispersed and stably loaded on the porous carbon skeleton, which inhibits the agglomeration and phase change of molybdenum carbide particles at high temperature, enhances its crystal phase stability and interface bonding strength with the carbon-based carrier.

[0036] In one embodiment, the carbonization treatment time is any value between 1.5h and 2.5h, for example, 1.5h, 2h or 2.5h. The carbonization heating rate is any value between 2°C / min and 10°C / min, for example, 2°C / min, 4°C / min, 6°C / min, 8°C / min or 10°C / min. Under the carbonization treatment conditions, while maintaining the integrity of the carbon-based skeleton structure, molybdenum carbide particles with stable crystal phase, uniform particle size and high dispersion can be obtained, thereby improving the specific surface area, electrical conductivity and intrinsic catalytic activity of the material in the hydrogen evolution reaction.

[0037] In one embodiment, jute powder adsorbed with a molybdenum-containing compound is pretreated before carbonization. The pretreatment step comprises reacting the jute powder adsorbed with the molybdenum-containing compound with a solution of a polyamine nitrogen source compound at 60°C-100°C for 1-4 hours to obtain an intermediate product. The reaction temperature can be, for example, 60°C, 70°C, 80°C, 90°C, or 100°C, and the reaction time can be, for example, 1 hour, 2 hours, 3 hours, or 4 hours. These conditions allow the introduction of nitrogen into the carbon-based skeleton, achieving nitrogen doping modification. The reaction mechanism of this nitrogen doping is as follows: nitrogen source molecules chemically bond with hydroxyl groups and residual protein groups on jute fiber-derived carbon, forming stable pyridinic and pyrrolic nitrogen-doped structures during the carbonization process, and constructing a Mo-NC ternary bond structure at the interface between the molybdenum carbide and the carbon skeleton. This structure enhances conductivity, provides stable anchoring sites for the molybdenum carbide particles, and inhibits particle migration.

[0038] In one embodiment, polyamine nitrogen source compound is selected from one or more combinations of ethylenediamine, diethylenetriamine and triethylenetetramine.Above-mentioned polyamine nitrogen source compound all has higher nitrogen content and multi-coordinate active site, can form stable complex with platinum ion, and is evenly doped into carbon skeleton during carbonization, so as to enhance the binding stability and catalytic activity of molybdenum carbide.The mass ratio of polyamine nitrogen source compound and jute powder is (0.5-2): arbitrary value in 1, for example, can be 0.5:1, 1:1, 1.25:1, 1.5:1 or 2:1.When the mass ratio is greater than 2:1, nitrogen content is too high in carbon skeleton, causes carbon skeleton defect excessive formation and reduces structural stability.When the mass ratio is less than 0.5:1, nitrogen doping amount is insufficient in carbon skeleton, is difficult to significantly improve the electronic structure and catalytic activity of carbon-based skeleton.

[0039] In one embodiment, the molybdenum carbide in the jute-derived porous carbon material loaded with molybdenum carbide has a particle size of any value between 20 nm and 60 nm, for example, 20 nm, 30 nm, 40 nm, 50 nm, or 60 nm. Within this particle size range, while maintaining the integrity of the carbon-based skeleton structure, molybdenum carbide particles with stable crystal phase, uniform particle size, and high dispersion can be obtained, thereby improving the material's specific surface area, electrical conductivity, and intrinsic catalytic activity in the hydrogen evolution reaction.

[0040] In one embodiment, a catalyst containing molybdenum carbide is provided, wherein the catalyst is prepared by the above-mentioned preparation method. In one embodiment, the catalyst containing molybdenum carbide is used as a catalytic material of an electric cathode and is used for hydrogen evolution reaction.

[0041] Example 1 Example 1 of the present invention provides a method for preparing a jute-derived porous carbon material loaded with molybdenum carbide, comprising the following steps: (1) Jute fiber was ultrasonically treated in ethanol and deionized water for 1 h, and then dried in an oven at 60°C until completely dry to obtain dried jute fiber.

[0042] (2) The dried jute fibers were pulverized in a multifunctional pulverizer at 28,000 rpm for 30 min, and then sieved through a 120-mesh sieve to obtain jute powder.

[0043] (3) 1 g of jute powder was immersed in 50 mL of 0.10 g / mL ammonium molybdate solution for 12 h to obtain a mixture.

[0044] (4) The mixture was taken out and dried in an oven at 60°C, and then carbonized in a tube furnace to obtain a jute-derived porous carbon material loaded with molybdenum carbide. The carbonization conditions were as follows: carbonization temperature of 900°C, carbonization atmosphere of nitrogen, carbonization time of 2 hours, and carbonization heating rate of 5°C / min.

[0045] Example 2 The only difference between Example 2 and Example 1 is that the carbonization treatment conditions in step (4) are as follows: the jute powder adsorbed with the molybdenum-containing compound is heated from room temperature to 340°C at a heating rate of 9°C / min and kept warm for 27 minutes, then heated from 340°C to 630°C at a heating rate of 5°C / min and kept warm for 25 minutes, then heated from 630°C to 900°C at a heating rate of 3°C / min and kept warm for 120 minutes, and the carbonization atmosphere is nitrogen.

[0046] Example 3 The only difference between Example 3 and Example 2 is that in step (4), the jute powder adsorbed with the molybdenum-containing compound is pretreated before being carbonized. The pretreatment step is as follows: 1 g of jute powder adsorbed with the molybdenum-containing compound and 1 g of ethylenediamine are reacted at 80° C. for 2 h to obtain an intermediate product, and then the intermediate product is further carbonized.

[0047] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that in step (3), 1 g of jute powder is immersed in 50 mL of 0.20 g / mL ammonium molybdate solution for 12 h to obtain a mixture.

[0048] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the carbonization temperature in step (4) is 1000°C.

[0049] Comparative Example 3 Comparative Example 3 provides a method for preparing a phenolic resin-derived porous carbon material loaded with molybdenum carbide, comprising the following steps: (1) Phenolic resin powder was dried at 80°C for 12 h in an air atmosphere and then carbonized at 700°C for 2 h in a nitrogen atmosphere to obtain phenolic resin-derived porous carbon powder.

[0050] (2) 1 g of the treated phenolic resin-derived porous carbon powder was added to 50 mL of a 0.10 g / mL ammonium molybdate solution and immersed at room temperature for 12 h to obtain a mixture.

[0051] (3) The mixture was removed and dried in an oven at 60°C, then placed in a tube furnace for carbonization. The carbonization conditions were as follows: in a nitrogen atmosphere, the temperature was increased from room temperature to 900°C at a rate of 5°C / min, maintained at that temperature for 2 hours, cooled to room temperature, and removed to obtain a phenolic resin-derived porous carbon material loaded with molybdenum carbide.

[0052] Figure 2 The SEM image of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention is shown. Figure 3 FIG1 shows an SEM image of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Comparative Example 1 of the present invention. Figure 2 and Figure 3 As shown, Example 1 shows uniformly distributed molybdenum carbide particles. The average particle size of the molybdenum carbide particles was measured to be 20nm, and the porous structure of the jute fiber was well preserved after carbonization, providing abundant anchoring sites for the molybdenum carbide particles. In Comparative Example 1, the molybdenum carbide particles agglomerated and could not be evenly distributed on the carbon substrate, and the active sites were reduced, which would affect its subsequent catalytic performance. This is because when the mass ratio of jute powder and molybdenum-containing compound solution is greater than 1:6.25, the molybdenum precursor in the solution appears supersaturated adsorption and crystallization on the support surface and in the pores, and is prone to forming a local high-concentration molybdenum species enrichment zone during drying and subsequent carbonization. The enrichment causes the nucleation density to be too high and early crystal nuclei to merge, ultimately inducing nanoparticle growth and agglomeration, and partially blocking the pores, reducing the number and distribution uniformity of effective anchoring sites, causing molybdenum carbide to be unable to achieve uniform dispersion on the carbon substrate. This shows that highly dispersed and stable loading of molybdenum carbide on a porous carbon skeleton can be achieved by precisely controlling the mass ratio.

[0053] Figure 4 The EDS graph of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention is shown. Figure 5 TEM image of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention is shown. Figure 6 HR-TEM image of jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention is shown. Figure 4 As shown, elemental mapping shows that molybdenum is evenly distributed throughout the carbon matrix, which will provide more active sites and further improve the efficiency of the catalytic reaction. At the same time, the uniform dispersion of molybdenum carbide helps to improve the conductivity of the material, thereby accelerating electron transfer and enhancing electrocatalytic performance. Figure 5 The TEM image also shows that the molybdenum carbide particles are evenly distributed on the carbon matrix. Figure 6 The HR-TEM image of the jute-derived porous carbon material loaded with molybdenum carbide showed that it had clear lattice fringes with a fringe spacing of 0.23 nm, which corresponds to the (101) plane of β-Mo2C, indicating that the attached molybdenum carbide had high crystallinity.

[0054] Figure 7 The XRD patterns of the jute-derived porous carbon materials loaded with molybdenum carbide prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown. Figure 7As shown, in Example 1, only the characteristic peak of β-Mo2C was detected in the diffraction pattern, and no heterogeneous peak appeared, indicating that the molybdenum species was completely carbonized and the material purity was high. And in Example 1, the characteristic peak half-width of β-Mo2C was large, and the peak shape was moderately broadened, reflecting that the nanocrystal size was small and well dispersed. In addition to the characteristic peak of molybdenum carbide, the diffraction peak of molybdenum dioxide also appeared in the diffraction pattern of Comparative Example 1, indicating that the molybdenum precursor was not completely converted into molybdenum carbide. This shows that when the mass ratio of jute powder and molybdenum-containing compound solution is greater than 1:6.25, the local concentration of molybdenum species is too high, agglomeration occurs during the carbonization process, and part of the molybdenum is not fully reduced, remaining as molybdenum dioxide, resulting in a decrease in purity, which will affect the catalytic performance of molybdenum carbide as a catalyst in the subsequent process. The sharp diffraction peak of metallic molybdenum appears in the diffraction pattern of Comparative Example 2, while the β-Mo2C peak intensity weakens, which may be related to the use of a higher carbonization temperature in the comparative example, resulting in a phase change in the grains of some molybdenum carbides, which will affect the structure and performance of the catalyst. The analysis results of the XRD spectrum show that by precisely controlling the carbonization temperature and mass ratio, Example 1 successfully prepared a jute-derived porous carbon material loaded with molybdenum carbide with high purity and good dispersion, thereby optimizing the crystal structure and electrocatalytic performance of the material.

[0055] Furthermore, the jute-derived porous carbon materials loaded with molybdenum carbide prepared in the examples and comparative examples were prepared into ink for electrochemical testing, which was then dropped onto a glassy carbon electrode for electrocatalytic hydrogen evolution reaction testing using a three-electrode system in an electrochemical workstation. The corresponding three-electrode system used the examples and comparative examples as working electrodes, Ag / AgCl as a reference electrode, and a carbon rod as an auxiliary electrode. This three-electrode system was used to test the electrochemical properties and hydrogen evolution reaction catalytic efficiency of the porous carbon materials loaded with molybdenum carbide prepared in Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0056] Table 1 below shows the cycling stability of the molybdenum carbide-based catalysts in Examples 1-3 of the present invention and Comparative Examples 1-3 in electrocatalysis.

[0057]

[0058] The cyclic stability test shown in Table 1 was conducted using cyclic voltammetry at a specific potential of -0.2 V using an electrochemical workstation. The results showed that the catalyst in Example 1 had a high initial activity, with an initial current density of 20 mA·cm -2 , and only slightly decreased after 10,000 cycles, indicating that it can still maintain stable catalytic performance under long-term cycling conditions. The initial current density of Example 2 and Example 3 is 22 mA·cm -2 and 25 mA·cm -2 , and after cycling, they were 21 mA·cm -2 and 24 mA·cm-2 , indicating that the staged heating process and nitrogen doping pretreatment further optimize the dispersibility and interfacial bonding of molybdenum carbide, thereby improving the utilization rate of active sites and long-term stability. In contrast, Comparative Examples 1-3 all show a lower initial current density, and show a significant decrease after cycling. In Comparative Example 1, when the mass ratio of jute powder to molybdenum compound solution is too large, it is easy to cause the precursor to be locally enriched and agglomerated. During the carbonization process, the molybdenum species fails to be completely reduced to nanoscale molybdenum carbide, resulting in a reduction in effective active sites. In Comparative Example 2, under excessively high carbonization temperature or unoptimized heating conditions, the carbon-based skeleton is prone to excessive graphitization, and the molybdenum carbide crystal phase undergoes partial phase change or even generates a miscellaneous phase, resulting in a decrease in interfacial bonding. In addition, the porous carbon material used in Comparative Example 3 has low mechanical strength and unstable pore structure, and pore collapse or structural rearrangement is prone to occur during the cycle. The above defects cause the catalyst in the comparative example to experience phenomena such as active site loss, particle migration and agglomeration under long-term circulation, thereby causing rapid decay of current density. Therefore, the present invention selects jute fiber-derived porous carbon supports with excellent structural stability, combines precise precursor mass ratio control, staged temperature increase carbonization strategy and nitrogen doping pretreatment, effectively inhibits the agglomeration and phase change of molybdenum carbide, enhances the interfacial bonding force between molybdenum carbide and the carbon skeleton, and maintains the porous structural integrity of the carbon skeleton, so that molybdenum carbide exhibits excellent cyclic stability.

[0059] Table 2 below shows the overpotentials of the molybdenum carbide-based catalysts in Examples 1-3 of the present invention and Comparative Examples 1-3 in electrocatalysis.

[0060]

[0061] Table 2 above at 10 mA·cm -2The electrocatalytic overpotential data of different embodiments and comparative examples were tested under current density. As shown in Table 2, the overpotential values ​​of Examples 1-3 are significantly lower than those of Comparative Examples 1-3, indicating that the use of jute fiber-derived porous carbon as a carrier not only effectively suppresses the agglomeration of molybdenum carbide particles, but also reduces the activation energy of hydrogen evolution reaction, improves the electron transfer efficiency of the carrier, thereby enhancing the intrinsic activity of the catalyst. Under the same carrier conditions, optimizing the carbonization treatment conditions can further improve the catalytic performance. For example, Example 2 adopts a staged heating strategy to achieve precise control of temperature and heating rate in each stage of devolatilization, nucleation and crystal growth, effectively suppressing the excessive grain growth of molybdenum carbide and the excessive graphitization of the carbon-based skeleton, thereby maintaining high-density active sites and excellent structural stability. Example 3 builds on this by introducing ethylenediamine for pretreatment. By introducing a nitrogen-doped structure into the carbon-based skeleton and constructing a Mo-NC ternary bond at the interface between the molybdenum carbide and the carbon-based structure, this not only further improves the interfacial bonding strength and electronic conductivity, but also promotes the uniform dispersion of molybdenum carbide particles on the support surface, reducing its overpotential to 180.39 mV. In contrast, Comparative Examples 1-3 suffer from problems such as insufficient support structure stability, unreasonable carbonization conditions, or inappropriate precursor loading ratios, which lead to easy agglomeration of molybdenum carbide, phase transition, or decreased interfacial bonding strength, resulting in increased overpotential and reduced catalytic activity.

[0062] Figure 8 Catalyst polarization curves of the jute-derived porous carbon materials loaded with molybdenum carbide prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown. Figure 9 The Tafel plots of the jute-derived porous carbon materials loaded with molybdenum carbide prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are shown. Figure 10 The long-term stability of the jute-derived porous carbon material loaded with molybdenum carbide prepared in Example 1 of the present invention is shown. Figure 8 As shown, the onset potential of Example 1 is low, and a higher current density is maintained in a wider potential range, indicating that the catalyst has higher activity and stability in hydrogen evolution reaction. In contrast, the onset potentials of Comparative Example 1 and Comparative Example 2 are significantly increased, and the current density at the same potential is low, reflecting that its electrocatalytic performance is insufficient. The reason for this difference is that the preparation method or material selection of the comparative example fails to take into account the number of active sites, electron transfer efficiency and structural stability at the same time, resulting in insufficient catalytic activity. Example 1 effectively improves the crystallinity and active site accessibility of molybdenum carbide by accurately controlling the carbonization temperature and the precursor loading ratio, and with a reasonable pretreatment step, while ensuring particle dispersibility and interfacial bonding force, thereby enhancing the reaction kinetics of hydrogen evolution reaction. Figure 9 The relationship between the logarithm of current density and potential is shown, which is an important parameter for measuring the kinetics of electrocatalytic reactions. The smaller the value, the faster the reaction kinetics. The Tafel slope of Example 1 is 63.48 mV·dec-1 , which is significantly lower than 170.59mV·dec of Comparative Example 1 -1 and 454.91mV·dec of Comparative Example 2 -1 , indicating that Example 1 can drive a higher current density at the same overpotential, that is, the faster the reaction kinetics, the more efficient the utilization of active sites and the faster electron transport capability. This excellent performance is attributed to the synergistic effect of the uniformly distributed nano-scale molybdenum carbide particles and the highly conductive porous carbon skeleton in Example 1, which significantly reduces the reaction activation energy and improves the mass transfer conditions of reactants / products at the electrode interface. In contrast, the comparative example samples have a blocked electron transport path and a reduced utilization of active sites due to particle agglomeration, phase change or unstable carrier structure, resulting in a significant increase in the Tafel slope. Figure 10 The results show that after 40 hours of continuous operation, the potential of Example 1 rose by only 35 mV, demonstrating extremely high electrochemical stability. This stability stems from the uniform anchoring and strong interfacial bonding of molybdenum carbide within the jute fiber-derived porous carbon framework, which effectively inhibits particle migration and agglomeration. Furthermore, the multi-level pore structure facilitates electrolyte penetration and reactant diffusion, reducing concentration polarization.

[0063] In summary, the present invention synergistically achieves fine-grained dispersion of molybdenum carbide particles, enhanced interface stability, and optimized electronic structure through the selection of high-strength porous carbon supports, optimization of precursor loading ratios, a staged temperature-raising carbonization strategy, and nitrogen-doping pretreatment, thereby significantly reducing the overpotential and improving the overall electrocatalytic performance.

[0064] The above are only some specific implementation methods of the present application. Any other improvements made based on the concept of the present application are considered to be within the scope of protection of the present application.

Claims

1. A method for preparing a jute-derived porous carbon material loaded with molybdenum carbide, characterized in that: The following steps are involved: pre-treating jute fibers to obtain jute powder; placing the jute powder in a molybdenum-containing compound solution to obtain a mixture, wherein the jute powder in the mixture is adsorbed with the molybdenum-containing compound, and a mass ratio of the jute powder to the molybdenum-containing compound in the molybdenum-containing compound solution is any value in the range of 1:(2.5-6.25); The jute powder adsorbed with the molybdenum-containing compound is carbonized at 800° C.-900° C. to obtain a jute-derived porous carbon material loaded with molybdenum carbide.

2. The preparation method according to claim 1, characterized in that The jute powder adsorbed with the molybdenum-containing compound is carbonized at 800° C. to 900° C. to obtain a jute-derived porous carbon material loaded with molybdenum carbide, comprising the following steps: The jute powder adsorbed with the molybdenum-containing compound is heated from room temperature to 300-400° C. at a heating rate of 8-10° C. / min and kept at this temperature for 20-30 minutes; Then, increase the temperature from 300-400°C to 600-700°C at a heating rate of 3-5°C / min and keep it at that temperature for 20-30 minutes. Then, the temperature is increased from 600°C-700°C to 800°C-900°C at a heating rate of 2°C / min-5°C / min, and kept at this temperature for 90min-150min.

3. The preparation method according to claim 2, characterized in that The step of carbonizing the jute powder adsorbed with the molybdenum-containing compound at 800° C. to 900° C. to obtain the jute-derived porous carbon material loaded with molybdenum carbide further includes pretreatment before the carbonization; In the pretreatment step, the jute powder adsorbed with the molybdenum-containing compound is reacted with a polyamine nitrogen source compound solution at 60° C.-100° C. for 1 h-4 h to obtain an intermediate product.

4. The preparation method according to claim 3, characterized in that The polyamine nitrogen source compound is selected from one or more combinations of ethylenediamine, diethylenetriamine and triethylenetetramine; The mass ratio of the polyamine nitrogen source compound to the jute powder is any value between (0.5-2):

1.

5. The preparation method according to claim 1, characterized in that In the step of taking out the jute powder adsorbed with the molybdenum-containing compound and drying it, and then carbonizing it to obtain a jute-derived porous carbon material loaded with molybdenum carbide, the carbonization time is any value between 1.5h and 2.5h, and the carbonization heating rate is any value between 2°C / min and 10°C / min.

6. The preparation method according to claim 1, characterized in that The solute in the molybdenum compound solution is selected from a combination of one or more of ammonium molybdate tetrahydrate, sodium molybdate and potassium molybdate.

7. The preparation method according to any one of claims 1 to 6, characterized in that The particle size of the molybdenum carbide in the jute-derived porous carbon material loaded with molybdenum carbide is any value between 20 nm and 60 nm.

8. The preparation method according to claim 1, characterized in that In the step of pre-treating jute fiber to obtain jute powder, the specific steps of the pre-treatment are: washing and drying the jute fibers to obtain treated jute fibers; The treated jute fibers are crushed and sieved to obtain jute powder.

9. A catalyst containing molybdenum carbide, characterized in that The catalyst containing molybdenum carbide is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the catalyst containing molybdenum carbide according to claim 9, characterized in that: The catalyst containing molybdenum carbide is used as a catalytic material of an electric cathode and is used for hydrogen evolution reaction.

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