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

Abstract

The application provides a preparation method and application of a molybdenum carbide loaded jute derived porous carbon material, and belongs to the technical field of electrochemical catalysis. The preparation method comprises the following steps: pretreating jute fibers to obtain jute powder; placing the jute powder in a molybdenum compound containing solution to obtain a mixture, the jute powder in the mixture adsorbing the molybdenum compound, and the mass ratio of the jute powder to the molybdenum compound in the molybdenum compound containing solution being any value in 1:(2.5-6.25); and carbonizing the jute powder adsorbing the molybdenum compound at 800-900 DEG C to obtain the molybdenum carbide loaded jute derived porous carbon material. The jute fiber derived porous carbon is used as a carrier, and the precursor is fully adsorbed and combined in the molybdenum compound containing solution. By adjusting the mass ratio and the carbonization temperature, the highly dispersed and stably loaded molybdenum carbide is realized, the structural stability and catalytic activity of the molybdenum carbide based catalyst are improved, and 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 commonly used 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 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:

[0006] The jute fibers are pretreated to obtain jute powder;

[0007] placing the jute powder into a solution containing a molybdenum compound to obtain a mixture, the jute powder in the mixture adsorbing the molybdenum compound, the mass ratio of the jute powder to the molybdenum compound in the solution being any value in the range of 1:(2.5-6.25);

[0008] carburizing the jute powder adsorbing the molybdenum compound at 800-900℃ to obtain a jute-derived porous carbon material loaded with carburized molybdenum.

[0009] Optionally, the step of carburizing the jute powder adsorbing the molybdenum compound at 800-900℃ to obtain a jute-derived porous carbon material loaded with carburized molybdenum includes the following steps:

[0010] raising the temperature of the jute powder adsorbing the molybdenum compound from room temperature to 300-400℃ at a temperature raising rate of 8-10℃ / min and maintaining the temperature for 20-30min;

[0011] raising the temperature from 300-400℃ to 600-700℃ at a temperature raising rate of 3-5℃ / min and maintaining the temperature for 20-30min;

[0012] raising the temperature from 600-700℃ to 800-900℃ at a temperature raising rate of 2-5℃ / min and maintaining the temperature for 90-150min.

[0013] Optionally, the step of carburizing the jute powder adsorbing the molybdenum compound at 800-900℃ to obtain a jute-derived porous carbon material loaded with carburized molybdenum further includes a pretreatment step before the carburization.

[0014] In the pretreatment step, the jute powder adsorbing the molybdenum compound is reacted with a solution of a polyamine nitrogen source compound at 60-100℃ for 1-4h to obtain an intermediate product.

[0015] Optionally, the polyamine nitrogen source compound is selected from a combination of one or more of ethylenediamine, diethylenetriamine and triethylenetetramine.

[0016] The mass ratio of the polyamine nitrogen source compound to the jute powder is any value in the range of (0.5-2):1.

[0017] Optionally, in the step of taking out the jute powder adsorbing the molybdenum compound and drying, and then carburizing to obtain a jute-derived porous carbon material loaded with carburized molybdenum, the carburization time is any value in the range of 1.5-2.5h and the carburization heating rate is any value in the range of 2-10℃ / min.

[0018] Optionally, the solute in the molybdenum-containing compound solution is selected from a combination of one or more of ammonium molybdate tetrahydrate, sodium molybdate and potassium molybdate.

[0019] Optionally, the particle size of the molybdenum carbide in the molybdenum carbide-loaded jute-derived porous carbon material is any value in a range from 20 nm to 60 nm.

[0020] Optionally, in the step of pretreating the jute fibers to obtain jute powder, the specific steps of the pretreatment are as follows:

[0021] The jute fibers are washed and dried to obtain treated jute fibers.

[0022] The treated jute fibers are crushed and sieved to obtain jute powder.

[0023] According to a second aspect of the present application, a molybdenum carbide-containing catalyst is provided, which is prepared by the aforementioned preparation method.

[0024] According to a third aspect of the present application, a use of the aforementioned molybdenum carbide-containing catalyst is provided, which is used as a catalytic material of an electric cathode and for a hydrogen evolution reaction.

[0025] According to the scheme of the present application, jute fiber-derived porous carbon is used as a carrier, and sufficient adsorption and combination of precursors are achieved in a molybdenum-containing compound solution. By accurately controlling the mass ratio and the carbonization temperature, the molybdenum carbide can be highly dispersed and stably loaded on the porous carbon skeleton. In addition, by combining the space confinement effect of the porous carbon skeleton with excellent mechanical robustness, the migration and structural degradation of the molybdenum carbide particles under electrochemical service conditions are effectively inhibited. The present application utilizes the natural multi-level pore structure and high carbon content of jute fibers to construct a conductive carbon-based skeleton with abundant pores during the carbonization process, thereby significantly improving the specific surface area and electron transport efficiency of the material. At the same time, by accurately controlling the carbonization temperature range and the heating rate, the agglomeration and phase transition of the molybdenum carbide particles at high temperatures are inhibited, and the crystal phase stability and the interface bonding strength between the molybdenum carbide and the carbon-based carrier are enhanced. Thus, the structural stability and catalytic activity of the molybdenum carbide-based catalyst can be significantly improved, and the catalytic efficiency of the hydrogen evolution reaction is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A schematic diagram of a preparation method of a molybdenum carbide-loaded jute-derived porous carbon material according to an embodiment of the present application is shown;

[0027] Figure 2 An SEM image of a molybdenum carbide-loaded jute-derived porous carbon material prepared in Example 1 of the present application is shown;

[0028] Figure 3An SEM image of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1 is shown;

[0029] Figure 4 An EDS image of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1 is shown;

[0030] Figure 5 A TEM image of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1 is shown;

[0031] Figure 6 A HR-TEM image of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1 is shown;

[0032] Figure 7 An XRD image of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1, Comparative Example 1 and Comparative Example 2 is shown;

[0033] Figure 8 A catalyst polarization plot of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1, Comparative Example 1 and Comparative Example 2 is shown;

[0034] Figure 9 A Tafel plot of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1, Comparative Example 1 and Comparative Example 2 is shown;

[0035] Figure 10 A long term stability plot of the molybdenum carbide supported jute derived porous carbon material prepared in Inventive Example 1 is shown. DETAILED DESCRIPTION

[0036] In order to make the above objectives, features and advantages of the present application more comprehensible and easily understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings for the convenience of description, and not all the structures. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0037] The terms "comprising" and "having" and any variations thereof in the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device 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 devices.

[0038] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. Those skilled in the art will recognize that the embodiments described herein can be combined with one another. Various features of the above-described embodiments can be combined in any combination. To simplify the present description, not all possible combinations of the above-described features are described, however, it is understood that any combination of features is within the scope of the present disclosure, as long as the combination is not contradictory.

[0039] Figure 1 A schematic diagram of a method for preparing a molybdenum carbide-loaded jute-derived porous carbon material according to an embodiment of the application is shown. As shown, the method includes the following steps: Figure 1

[0040] S1, pretreating jute fibers to obtain jute powder.

[0041] S2, placing the jute powder in a solution containing a molybdenum compound to obtain a mixture, the jute powder in the mixture adsorbing the molybdenum compound, the mass ratio of the jute powder to the molybdenum compound in the solution being any value in the range of 1:(2.5-6.25).

[0042] S3, carbonizing the jute powder adsorbing the molybdenum compound at a temperature in the range of 800-900°C to obtain a molybdenum carbide-loaded jute-derived porous carbon material.

[0043] According to the scheme of the application, jute fiber-derived porous carbon is used as a carrier, and sufficient adsorption of the precursor is achieved in a solution containing a molybdenum compound, combined with precise control of the mass ratio and carbonization temperature, so that the molybdenum carbide can be highly dispersed and stably loaded on the porous carbon skeleton. In addition, the spatial confinement effect of the porous carbon skeleton combined with excellent mechanical robustness effectively suppresses the migration and structural degradation of the molybdenum carbide particles under electrochemical service conditions. The application takes advantage of the natural multi-level pore structure and high carbon content of jute fibers to construct a conductive carbon-based skeleton with abundant pores during the carbonization process, thereby significantly improving the specific surface area and electron transport efficiency of the material. At the same time, by precisely controlling the carbonization temperature range, the agglomeration and phase transition of the molybdenum carbide particles at high temperatures are suppressed, enhancing the crystal phase stability and interface bonding strength with the carbon-based carrier. Thus, the application can significantly improve the structural stability and catalytic activity of the molybdenum carbide-based catalyst, further improving the catalytic efficiency of the hydrogen evolution reaction.

[0044] ​In step S1, the jute fibers are pretreated to remove surface impurities and moisture and to homogenize their structure, thereby obtaining jute powder of suitable particle size and purity for subsequent efficient adsorption of molybdenum-containing compounds. In an embodiment, the specific steps of the pretreatment are as follows:

[0045] S101, the jute fibers are washed and dried to obtain treated jute fibers.

[0046] S102, the treated jute fibers are crushed and sieved to obtain jute powder.

[0047] In step S101, the jute fibers are ultrasonically cleaned in ethanol and deionized water for 1-2 h, for example, 1 h, 1.5 h, or 2 h, to remove impurities. The cleaned jute fibers are then dried to obtain treated jute fibers.

[0048] In step S102, the crushing treatment is performed at a rotation speed of any value in the range of 25,000 rpm-32,000 rpm, for example, 25,000 rpm, 28,500 rpm, or 32,000 rpm. The crushing time is any value in the range of 25 min-35 min, for example, 25 min, 30 min, or 35 min. The sieving uses a screen selected from a 120-mesh screen or a 150-mesh screen. Under the above crushing and sieving conditions, jute powder with uniform particle size and good dispersibility can be obtained, thereby increasing the specific surface area and surface active sites and improving the efficiency of contact and adsorption with the molybdenum-containing compound solution.

[0049] In step S2, the solute in the molybdenum-containing compound solution is selected from one or a combination of more than one 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 of molybdenum carbide, enabling uniform adsorption and anchoring of the molybdenum element on the surface of the jute powder and laying a foundation for the formation of nanoscale molybdenum carbide particles in the subsequent carbonization process. In an embodiment, the 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), for example, 1:2.5, 1:3, 1:3.5, 1:4.375, 1:4.5, 1:5, 1:5.5, or 1:6.25, or any value in the range of 1:(2.5-6.25). When the mass ratio is greater than 1:6.25, it is easy to cause the molybdenum carbide particles to agglomerate, increase in particle size, and reduce the active sites. When the mass ratio is less than 1:2.5, it will cause insufficient molybdenum content and reduced catalytic activity. In an embodiment, the jute powder is immersed in the molybdenum-containing compound solution for 10-14 h, for example, 10 h, 12 h, or 14 h, to reach adsorption equilibrium, so that the molybdenum-containing compound is fully combined and uniformly distributed on the surface of the jute powder, ensuring uniformity of the particle size and distribution of the molybdenum carbide in the subsequent carbonization process.

[0050] In step S3, the carbonization treatment adopts a staged temperature rising carbonization, including the following steps:

[0051] S301, the jute powder adsorbed with the molybdenum-containing compound is heated from room temperature to 300-400℃ at a temperature rising rate of 8-10℃ / min, and is kept for 20-30min.

[0052] S302, then heated from 300-400℃ to 600-700℃ at a temperature rising rate of 3-5℃ / min, and is kept for 20-30min.

[0053] S303, then heated from 600-700℃ to 800-900℃ at a temperature rising rate of 2-5℃ / min, and is kept for 90-150min.

[0054] In step S301, the temperature rising rate is any value in the range of 8-10℃ / min, for example, it can be 8℃ / min, 9℃ / min or 10℃ / min. The temperature rising 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-medium temperature preheating stage, the residual water and low molecular organic matters in the jute powder are removed, avoiding the pore structure collapse due to volatilization in the subsequent high temperature carbonization process.

[0055] In step S302, the temperature rising rate is any value in the range of 3-5℃ / min, for example, it can be 3℃ / min, 4℃ / min or 5℃ / min. The temperature rising 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.

[0056] In step S303, the temperature rising rate is any value between 2℃ / min and 5℃ / min, for example, it can be 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min. The temperature rising temperature is from 600℃ to 700℃ to 800℃ to 900℃, for example, it can be 800℃, 820℃, 840℃, 850℃, 860℃, 880℃ or 900℃. The holding time is any value between 90min and 150min, for example, it can be 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 high dispersion, and at the same time, the porous structure integrity of the carbon-based skeleton is maintained.

[0057] Through the above-mentioned high-temperature carbonization treatment with staged temperature rising, the molybdenum carbide is highly dispersed and stably loaded on the porous carbon skeleton, the agglomeration and phase transition of the molybdenum carbide particles at high temperature are inhibited, and the crystal phase stability and the interface bonding strength of the molybdenum carbide particles with the carbon-based carrier are enhanced.

[0058] In one embodiment, the carbonization treatment time is any value between 1.5h and 2.5h, for example, it can be 1.5h, 2h or 2.5h. The carbonization heating rate is any value between 2℃ / min and 10℃ / min, for example, it can be 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min or 10℃ / min. Under this carbonization treatment condition, the molybdenum carbide particles with stable crystal phase, uniform particle size and high dispersion can be obtained while maintaining the integrity of the carbon-based skeleton structure, thereby improving the specific surface area, electrical conductivity and intrinsic catalytic activity in the hydrogen evolution reaction of the material.

[0059] In one embodiment, before the jute powder adsorbed with the molybdenum-containing compound is subjected to carbonization treatment, it is pretreated. The pretreatment step is: reacting the jute powder adsorbed with the molybdenum-containing compound with a polyamine nitrogen source compound solution at 60℃ to 100℃ for 1h to 4h to obtain an intermediate product. The reaction temperature can be, for example, 60℃, 70℃, 80℃, 90℃ or 100℃, and the reaction time can be, for example, 1h, 2h, 3h or 4h. Through the above-mentioned conditions, nitrogen elements can be introduced into the carbon-based skeleton to achieve nitrogen-doped modification. The reaction mechanism of the nitrogen doping is: the nitrogen source molecules chemically combine with the hydroxyl groups and residual protein groups of the jute fiber-derived carbon to form stable pyridine-type nitrogen and pyrrole-type nitrogen doped structures in the carbonization process, and a Mo-N-C ternary bond structure is constructed at the interface of the molybdenum carbide and the carbon skeleton. This structure can enhance the electrical conductivity and provide stable anchoring sites for the molybdenum carbide particles to inhibit the migration of the particles.

[0060] In one embodiment, the polyamine nitrogen source compound is selected from a combination of one or more of ethylenediamine, diethylenetriamine, and triethylenetetramine. The above polyamine nitrogen source compounds all have high nitrogen content and multiple coordination active sites, can form stable complexes with molybdenum ions, and are uniformly doped into the carbon skeleton during carbonization, thereby enhancing the binding stability and catalytic activity of molybdenum carbide. The mass ratio of the polyamine nitrogen source compound to the jute powder is any value in the range of (0.5-2):1, for example, it 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, the nitrogen content in the carbon skeleton is too high, causing excessive formation of carbon skeleton defects and reducing the structural stability. When the mass ratio is less than 0.5:1, the nitrogen doping amount in the carbon skeleton is insufficient, and it is difficult to significantly improve the electronic structure and catalytic activity of the carbon-based skeleton.

[0061] In one embodiment, the particle size of the molybdenum carbide in the jute-derived porous carbon material loaded with molybdenum carbide is any value in the range of 20-60 nm, for example, it can be 20 nm, 30 nm, 40 nm, 50 nm, or 60 nm. When the particle size of the molybdenum carbide is in this range, it is possible to obtain molybdenum carbide particles that are stable in crystal phase, uniform in particle size, and highly dispersed, while maintaining the integrity of the carbon-based skeleton structure, thereby improving the specific surface area, electrical conductivity, and intrinsic catalytic activity in the hydrogen evolution reaction of the material.

[0062] In one embodiment, a catalyst containing molybdenum carbide is provided, which is prepared by the aforementioned preparation method. In one embodiment, the catalyst containing molybdenum carbide is used as a catalytic material for the electric cathode and in the hydrogen evolution reaction.

[0063] Embodiment 1

[0064] Embodiment 1 of the present application provides a preparation method of a jute-derived porous carbon material loaded with molybdenum carbide, which comprises the following steps:

[0065] (1) The jute fibers are 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 fibers.

[0066] (2) The dried jute fibers are crushed in a multifunctional crusher at 28000 rpm for 30 min, and then sieved using a 120-mesh sieve to obtain jute powder.

[0067] (3) 1 g of jute powder is immersed in 50 mL of an ammonium molybdate solution with a concentration of 0.10 g / mL for 12 h to obtain a mixture.

[0068] (4) The mixture was taken out and dried in an oven at 60℃, and then subjected to carbonization treatment in a tube furnace. After the carbonization was completed, a molybdenum carbide-loaded jute derivative porous carbon material was obtained. The carbonization treatment conditions were as follows: carbonization temperature 900℃, carbonization atmosphere nitrogen, carbonization time 2h, and carbonization heating rate 5℃ / min.

[0069] Example 2

[0070] Example 2 differs from Example 1 only in that the carbonization treatment conditions in step (4) were as follows: the jute powder adsorbed with the molybdenum-containing compound was heated at a temperature increasing rate of 9℃ / min from room temperature to 340℃, and then held for 27min, heated at a temperature increasing rate of 5℃ / min from 340℃ to 630℃, and then held for 25min, and heated at a temperature increasing rate of 3℃ / min from 630℃ to 900℃, and then held for 120min, and the carbonization atmosphere was nitrogen.

[0071] Example 3

[0072] Example 3 differs from Example 2 only in that the jute powder adsorbed with the molybdenum-containing compound was pretreated before being subjected to the carbonization treatment in step (4). The pretreatment step was as follows: 1g of the jute powder adsorbed with the molybdenum-containing compound and 1g of ethylenediamine were reacted at 80℃ for 2h to obtain an intermediate product, and then the intermediate product was subjected to further carbonization treatment.

[0073] Comparative Example 1

[0074] Comparative Example 1 differs from Example 1 only in that 1g of jute powder was immersed in 50mL of an ammonium molybdate solution having a concentration of 0.20g / mL in step (3), and the immersion was performed for 12h to obtain a mixture.

[0075] Comparative Example 2

[0076] Comparative Example 2 differs from Example 1 only in that the carbonization temperature in step (4) was 1000℃.

[0077] Comparative Example 3

[0078] The comparative example 3 provides a method for preparing a molybdenum carbide-loaded phenolic resin derivative porous carbon material, which comprises the following steps:

[0079] (1) Phenolic resin powder was taken, dried at 80℃ for 12h in an air atmosphere, and then carbonized at 700℃ for 2h in a nitrogen atmosphere to obtain phenolic resin derivative porous carbon powder.

[0080] (2) 1g of the treated phenolic resin derivative porous carbon powder was added to 50mL of an ammonium molybdate solution having a concentration of 0.10g / mL, and immersed at room temperature for 12h to obtain a mixture.

[0081] (3) The mixture was taken out and dried in an oven at 60 °C, and then placed in a tube furnace for carbonization treatment. The carbonization conditions were as follows: under a nitrogen atmosphere, the temperature was raised to 900 °C at a rate of 5 °C / min from room temperature, and kept for 2 h, and then taken out after cooling to room temperature, to obtain the carbonized molybdenum-loaded phenolic resin-derived porous carbon material.

[0082] Figure 2 An SEM image of the jute-derived porous carbon material loaded with carbonized molybdenum prepared in Example 1 of the present application is shown. Figure 3 An SEM image of the jute-derived porous carbon material loaded with carbonized molybdenum prepared in Comparative Example 1 of the present application is shown. As Figure 2 and Figure 3 shown, Example 1 exhibited uniformly distributed carbonized molybdenum particles, and the average particle size of the carbonized molybdenum particles was measured to be 20 nm, and the porous structure of the jute fibers was well preserved after carbonization, providing abundant anchoring sites for the carbonized molybdenum particles. In Comparative Example 1, the carbonized molybdenum particles were agglomerated and could not be uniformly distributed on the carbon substrate, and the active sites were reduced, which would affect the subsequent catalytic performance. This is because when the mass ratio of jute powder to molybdenum-containing compound solution is greater than 1:6.25, the molybdenum precursor in the solution is supersaturated and precipitates on the surface and in the pores of the carrier, and during the drying and subsequent carbonization process, local high-concentration molybdenum species enrichment areas are easily formed. This enrichment leads to a high nucleation density and early crystal nucleus coalescence, ultimately inducing nanoparticle growth and agglomeration, and partially blocking the pores, reducing the number and uniformity of effective anchoring sites, resulting in the inability of the carbonized molybdenum to be uniformly dispersed on the carbon substrate. This indicates that by precisely controlling the mass ratio, highly dispersed and stable loading of carbonized molybdenum on the porous carbon skeleton can be achieved.

[0083] Figure 4 An EDS image of the jute-derived porous carbon material loaded with carbonized molybdenum prepared in Example 1 of the present application is shown. Figure 5 A TEM image of the jute-derived porous carbon material loaded with carbonized molybdenum prepared in Example 1 of the present application is shown. Figure 6 A HR-TEM image of the jute-derived porous carbon material loaded with carbonized molybdenum prepared in Example 1 of the present application is shown. As Figure 4 shown, the element mapping showed that the molybdenum element was uniformly distributed throughout the carbon matrix, which would provide more active sites and further improve the efficiency of the catalytic reaction. At the same time, the uniform dispersion of carbonized molybdenum would help to improve the electrical conductivity of the material, thereby accelerating electron transfer and improving the electrocatalytic performance. Figure 5 The TEM image also showed carbonized molybdenum particles uniformly distributed and anchored on the carbon matrix, and Figure 6The HR-TEM images show that the jute-derived porous carbon material loaded with molybdenum carbide has clear lattice stripes with a stripe spacing of 0.23 nm, which corresponds to the (101) facet of β-Mo2C, indicating that the attached molybdenum carbide has high crystallinity.

[0084] Figure 7 The XRD patterns of the molybdenum carbide-loaded jute-derived porous carbon materials prepared in Examples 1, 1, and 2 of this invention are shown. Figure 7 As shown, in Example 1, only the characteristic peak of β-Mo2C was detected in the diffraction pattern, with no impurity peaks, indicating that the molybdenum species were completely carbonized and the material purity was high. Furthermore, the β-Mo2C characteristic peak in Example 1 had a large half-width and moderately broadened peak shape, reflecting small and well-dispersed nanocrystals. In contrast, the diffraction pattern of Comparative Example 1 showed not only the characteristic peaks of molybdenum carbide but also diffraction peaks of molybdenum dioxide, indicating that the molybdenum precursor was not completely converted to molybdenum carbide. This suggests that when the mass ratio of jute powder to the molybdenum-containing compound solution is greater than 1:6.25, the local concentration of molybdenum species is too high, leading to agglomeration during carbonization. Some molybdenum is not fully reduced, remaining as molybdenum dioxide, resulting in reduced purity. This will affect the catalytic performance of molybdenum carbide as a subsequent catalyst. The diffraction pattern of Comparative Example 2 showed sharp diffraction peaks of metallic molybdenum, while the intensity of the β-Mo2C peak weakened. This may be related to the higher carbonization temperature used in this comparative example, causing a phase transition in some molybdenum carbide grains, which will affect the structure and performance of the catalyst. XRD analysis results show that, by precisely controlling the carbonization temperature and mass ratio, Example 1 successfully prepared a jute-derived porous carbon material with high purity and good dispersibility loaded with molybdenum carbide, thereby optimizing the crystal structure and electrocatalytic performance of the material.

[0085] Furthermore, the molybdenum carbide-loaded jute-derived porous carbon materials prepared in the examples and comparative examples were used to prepare an electrochemical testing ink. This ink was then dropped onto a glassy carbon electrode for electrocatalytic hydrogen evolution reaction testing using a three-electrode system in an electrochemical workstation. In the corresponding three-electrode system, the examples and comparative examples served as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the auxiliary electrode. The electrochemical performance and hydrogen evolution reaction catalytic efficiency of the molybdenum carbide-loaded porous carbon materials prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were tested using this three-electrode system.

[0086] Table 1 below shows the cycling stability of the molybdenum carbide-based catalysts in electrocatalysis in Examples 1-3 and Comparative Examples 1-3 of the present invention.

[0087]

[0088] The cycle stability test shown in Table 1 above was carried out by an electrochemical workstation using cyclic voltammetry at a specific potential of -0.2 V. The results show that the catalyst in Example 1 has a high initial activity, with an initial current density of 20 mA·cm -2 , which only decreases slightly after 10,000 cycles, indicating that it can still maintain stable catalytic performance under long-term cycling conditions. The initial current densities of Examples 2 and 3 are 22 mA·cm -2 and 25 mA·cm -2 , respectively, and after cycling, they are 21 mA·cm -2 and 24 mA·cm -2 , respectively, indicating that the staged temperature rising process and nitrogen-doped pretreatment further optimize the dispersity and interface binding force of molybdenum carbide, thereby improving the active site utilization rate and long-term stability. In contrast, Comparative Examples 1-3 all exhibit low initial current densities and significant decreases after cycling. In Comparative Example 1, when the mass ratio of jute powder to molybdenum-containing compound solution is too large, the precursor is prone to accumulate and agglomerate locally, and the molybdenum species is not completely reduced to nanoscale molybdenum carbide during carbonization, resulting in a decrease in effective active sites. In Comparative Example 2, under excessively high carbonization temperature or non-optimized temperature rising conditions, the carbon-based skeleton is prone to excessive graphitization, and the molybdenum carbide crystal phase undergoes partial phase transformation or even generates a heterogeneous phase, resulting in a decrease in interface binding force. In addition, the porous carbon material used in Comparative Example 3 has low mechanical strength and unstable pore structure, and is prone to pore collapse or structural rearrangement during cycling. The above defects cause the catalyst in the comparative examples to lose active sites, migrate and agglomerate during long-term cycling, thereby causing rapid decay of the current density. Therefore, by selecting a jute fiber-derived porous carbon support with excellent structural stability, combining precise precursor mass ratio control, a staged temperature rising carbonization strategy, and nitrogen-doped pretreatment, the present application effectively inhibits the agglomeration and phase transformation of molybdenum carbide, enhances the interface binding force between molybdenum carbide and the carbon skeleton, and maintains the integrity of the porous structure of the carbon skeleton, enabling molybdenum carbide to exhibit excellent cycle stability.

[0089] Table 2 below shows the overpotential of the molybdenum carbide-based catalysts in the present application in Example 1-3 and Comparative Examples 1-3 in electrocatalysis.

[0090]

[0091] 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 embodiments 1-3 were 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 inhibited the agglomeration of molybdenum carbide particles, but also reduced the activation energy of the hydrogen evolution reaction, improved the electron transport efficiency of the carrier, and thus enhanced the intrinsic activity of the catalyst. Under the same carrier conditions, optimizing the carbonization treatment conditions can further improve the catalytic performance. For example, embodiment 2 adopts a staged temperature rising strategy to realize precise control of temperature and heating rate at each stage of devolatilization, nucleation and crystal growth, effectively inhibiting the excessive grain growth of molybdenum carbide and the excessive graphitization of the carbon-based skeleton, thereby maintaining a high density of active sites and excellent structural stability. Embodiment 3 introduces ethylenediamine pretreatment on this basis, introducing nitrogen-doped structures into the carbon-based skeleton and constructing Mo-N-C ternary bonds at the interface between molybdenum carbide and carbon, which not only further improves the interface bonding and electron conductivity, but also promotes the uniform dispersion of molybdenum carbide particles on the surface of the carrier, reducing the overpotential to 180.39 mV. In contrast, comparative examples 1-3 have problems such as insufficient structural stability of the carrier, unreasonable carbonization conditions, or improper precursor loading ratio, which leads to agglomeration, phase transition or decreased interface bonding of molybdenum carbide, thereby causing an increase in overpotential and a decrease in catalytic activity.

[0092] Figure 8 A catalyst polarization curve graph of the jute derived porous carbon material loaded with molybdenum carbide prepared in embodiment 1, comparative example 1 and comparative example 2 of the present application is shown. Figure 9 A Tafel curve graph of the jute derived porous carbon material loaded with molybdenum carbide prepared in embodiment 1, comparative example 1 and comparative example 2 of the present application is shown. Figure 10 A long-term stability graph of the jute derived porous carbon material loaded with molybdenum carbide prepared in embodiment 1 of the present application is shown. As shown in Figure 8 The starting potential of embodiment 1 is low, and a high current density is maintained within a wide potential interval, indicating that the catalyst has high activity and stability in the hydrogen evolution reaction. In contrast, the starting potential of comparative examples 1 and 2 is significantly higher, and the current density at the same potential is lower, reflecting the insufficient electrocatalytic performance. The reason for this difference is that the preparation method or material selection of the comparative examples fails to simultaneously consider the number of active sites, electron transport efficiency and structural stability, resulting in insufficient catalytic activity. Embodiment 1 precisely controls the carbonization temperature and precursor loading ratio, and cooperates with a reasonable pretreatment step, effectively improving the crystallinity of molybdenum carbide and the accessibility of active sites, while ensuring particle dispersion and interface bonding, thereby enhancing the reaction kinetics of the hydrogen evolution reaction. Figure 9 The relationship between the logarithm of current density and potential is an important parameter for measuring the electrocatalytic reaction kinetics, and the smaller the value, the faster the reaction kinetics. The Tafel slope of embodiment 1 is 63.48 mV·dec-1 , which is significantly lower than 170.59 mV dec-1 of Comparative Example 1 -1 and 454.91 mV dec-1 of Comparative Example 2 -1 , indicating that Example 1 can drive higher current density at the same overpotential, i.e. faster reaction kinetics, reflecting the efficient utilization of active sites and fast electron transport ability. This excellent performance is attributed to the synergistic effect of uniformly distributed nanoscale molybdenum carbide particles and highly conductive porous carbon framework 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 sample of the comparative example is blocked by the electron transport path and the utilization rate of active sites due to particle agglomeration, phase change or unstable carrier structure, resulting in a significant increase in the Tafel slope. Figure 10 It is shown in Table 2 that the potential of Example 1 only rises by 35 mV after 40 h of continuous operation, showing extremely high electrochemical stability. This stability is due to the uniform anchoring and strong interface binding of molybdenum carbide on the jute fiber derived porous carbon framework, effectively inhibiting particle migration and agglomeration. At the same time, the multi-level pore structure promotes electrolyte penetration and reactant diffusion, reducing concentration polarization.

[0093] In summary, the present application synergistically realizes fine-grained dispersion, interface stability enhancement and electronic structure optimization of molybdenum carbide particles by the selection of high-strength porous carbon carriers, the optimization of precursor loading ratio, the staged temperature rising carbonization strategy and the nitrogen-doped pretreatment, thereby significantly reducing the overpotential and improving the overall electrocatalytic performance.

[0094] The above are only some specific embodiments of the present application, and any improvement made on the basis of the concept of the present application is 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, Includes the following steps: Jute fibers are pretreated to obtain jute powder; The jute powder is placed in a molybdenum-containing compound solution to obtain a mixture in which the jute powder adsorbs the molybdenum-containing compound, and the 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). Jute powder adsorbed with molybdenum compounds was carbonized at 800℃-900℃ to obtain jute-derived porous carbon material loaded with molybdenum carbide. The process of carbonizing jute powder adsorbed with molybdenum compounds at 800℃-900℃ to obtain jute-derived porous carbon material loaded with molybdenum carbide includes the following steps: The jute powder adsorbed with molybdenum compounds was heated from room temperature to 300℃-400℃ at a heating rate of 8℃ / min-10℃ / min and held at that temperature for 20min-30min. Then, increase the temperature from 300℃-400℃ to 600℃-700℃ at a rate of 3℃ / min-5℃ / min, and hold for 20min-30min. Then, increase the temperature from 600℃-700℃ to 800℃-900℃ at a rate of 2℃ / min-5℃ / min, and hold for 90min-150min. The step of carbonizing jute powder adsorbed with molybdenum compounds at 800℃-900℃ to obtain jute-derived porous carbon material loaded with molybdenum carbide also includes pretreatment before carbonization. In the pretreatment step, the jute powder adsorbed with molybdenum-containing compounds is reacted with a polyamine nitrogen source compound solution at 60℃-100℃ for 1h-4h to obtain an intermediate product.

2. The preparation method according to claim 1, 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 in the range of (0.5-2):

1.

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

4. The preparation method according to any one of claims 1-3, characterized in that, 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.

5. The preparation method according to claim 1, characterized in that, In the step of pretreating jute fibers to obtain jute powder, the specific steps of the pretreating process are as follows: The jute fiber is obtained by washing and drying the jute fiber; The processed jute fibers are crushed and sieved to obtain jute powder.

6. A catalyst containing molybdenum carbide, characterized in that, The catalyst containing molybdenum carbide is prepared by the preparation method described in any one of claims 1-5.

7. Use of a catalyst containing molybdenum carbide as described in claim 6, characterized in that, The catalyst containing molybdenum carbide is used as a catalytic material for the cathode and for the hydrogen evolution reaction.

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