Cobalt phosphide and carbon fiber composite catalytic material and preparation method thereof

Abstract

The invention discloses a cobalt phosphide and carbon fiber composite catalytic material and a preparation method thereof, and belongs to the technical field of electro-catalysis. The method comprises the following steps: dissolving cobalt chloride hexahydrate, sodium dihydrogen phosphate and a surfactant in deionized water, uniformly stirring, carrying out solvent heat treatment, washing, drying and carrying out heat treatment to obtain cobalt phosphide microspheres; the preparation method comprises the following steps: dissolving polyacrylonitrile in N, N-dimethylformamide to obtain a suspension; adding cobalt phosphide microspheres into the suspension liquid, and uniformly stirring to form an electrospinning liquid; and carrying out electrostatic spinning on the electrospinning liquid, and drying to obtain the cobalt phosphide and carbon fiber composite catalytic material. The polyacrylonitrile fiber has excellent conductivity and a large specific surface area, the polyacrylonitrile fiber is adopted as a carbon carrier and is loaded with cobalt phosphide microspheres, the conductivity of the catalytic material is improved, more catalytic active sites are provided, a stable catalytic structure is formed, and the electro-catalytic performance is remarkably improved; the problem that a traditional non-noble metal catalyst is prone to inactivation in an acid environment is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and in particular relates to a cobalt phosphide and carbon fiber composite catalytic material and a preparation method thereof. Background Art

[0002] Energy supplies derived from fossil fuels face limited reserves and environmental pollution. Developing clean, low-cost, efficient, and renewable energy sources is an effective strategy for achieving sustainable development. Energy conversion devices, such as water electrolysis for hydrogen production, fuel cells, and metal-air batteries, play a crucial role in the development and application of new energy sources. However, the oxygen reduction reaction (ORR) at the cathode of fuel cells and the oxygen evolution reaction (OER) at the anode of water electrolysis devices exhibit slow or even nonexistent kinetics. Therefore, efficient electrocatalytic ORR and OER reactions are crucial for these energy conversion technologies. Electrocatalysis, a key branch of electrochemistry, involves electrochemical reactions occurring at the interface between electrolytes and electrodes. It investigates the relationship between the physicochemical properties of electrode materials and the reaction mechanisms and rates. Electrocatalysis aims to increase the reaction rate by reducing the activation energy of the target reaction. This reduction can be achieved by altering the interaction between the reactants and the electrode surface or by modifying the reaction pathway. Therefore, catalytic materials are often used directly as electrodes or modified with electrocatalysts to enhance the reaction rate. There are two types of electrocatalytic reaction processes. One is the transfer of molecules or ions to the catalyst surface to produce chemical reaction intermediates. The adsorbed intermediates can produce stable molecules through a chemical desorption process. For example, hydrogen evolution reaction, oxygen evolution reaction and oxygen reduction reaction are all reactions of this type. The other is the chemical adsorption of reactants on the catalyst or electrode surface, followed by electron transfer or electrochemical reaction, such as methanol oxidation reaction, ethanol oxidation reaction, formic acid oxidation reaction, etc.

[0003] At present, noble metals such as ruthenium and iridium and their oxides have high electrocatalytic activity and can improve oxygen evolution efficiency, but factors such as high price and low reserves have severely limited their commercial application. Although transition metal phosphides have shown great application prospects in the field of water electrolysis due to their excellent electrocatalytic performance, they still face some challenges in practical applications, such as the tendency of transition metals to leach and dissolve in acidic environments, leading to catalyst deactivation, and the need to further improve their conductivity and stability. In order to solve the above problems, researchers have been exploring new non-noble metal catalysts. Among them, carbon materials are an ideal catalyst support material due to their excellent conductivity and large specific surface area. The Chinese patent application with publication number CN116463659A discloses a cobalt-iron bimetallic phosphide electrocatalytic material with a one-dimensional morphology, its preparation method and application. This patent dissolves cobalt nitrate and ferric nitrate in a mixture of ethanol and N,N-dimethylformamide, adds polyvinyl pyrrolidone, and electrospins, dries, and calcines to obtain cobalt ferrite nanofibers. The cobalt ferrite nanofibers and sodium hypophosphite are then placed separately in a tube furnace and calcined under a protective gas atmosphere to obtain a cobalt-iron bimetallic phosphide electrocatalyst material with a one-dimensional morphology. However, this patent still has the problem that the morphology and structure of the electrocatalyst material need to be further optimized to improve its electrocatalytic performance. Chinese patent application with publication number CN113417032A discloses a preparation method and application of a nitrogen-doped mesoporous carbon fiber-based non-precious metal electrocatalyst. This patent dissolves polyacrylonitrile in an organic solution, then dissolves diisopropyl azodicarboxylate, cobalt acetate tetrahydrate, and iron acetylacetonate in the organic solution containing polyacrylonitrile in sequence, performs electrospinning to obtain a spinning precursor, and then obtains a nitrogen-doped mesoporous carbon fiber-based non-precious metal electrocatalyst through curing and carbonization. However, this patent still has the problem that the performance and stability of the electrocatalyst need to be further improved.

[0004] In the process of hydrogen production by electrolysis of water, the anodic oxygen evolution reaction of existing electrocatalytic materials involves four-electron transfer, and the reaction kinetics are slow, resulting in high energy consumption, which seriously restricts the commercial application of hydrogen production by electrolysis of water. Traditional precious metal-based catalysts, although they have high electrocatalytic activity, are severely limited by factors such as their high price and low reserves. Existing non-precious metal catalysts are prone to leaching and dissolution in acidic environments, leading to catalyst deactivation, and their conductivity and stability need to be improved. The active components have poor dispersion and stability in carbon supports, making it difficult to form a uniform composite structure, which affects the improvement of electrocatalytic performance. How to evenly disperse the active components in the carbon support to form a stable composite structure while maintaining good conductivity and catalytic activity remains the focus and difficulty of current research. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a cobalt phosphide and carbon fiber composite catalytic material and a preparation method thereof, so as to solve the technical problems of the existing electrocatalytic materials in the process of electrolysis of water to produce hydrogen, such as slow anode oxygen evolution reaction rate, easy deactivation of non-precious metal catalysts in acidic environments, and poor dispersion of active components in carbon supports.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing a cobalt phosphide and carbon fiber composite catalytic material, comprising the following steps: Cobalt chloride hexahydrate, sodium dihydrogen phosphate and a surfactant are dissolved in deionized water, stirred evenly, subjected to solvent heat treatment, and then washed, dried and heat treated to obtain cobalt phosphide microspheres; dissolving polyacrylonitrile in N, N-dimethylformamide to obtain a suspension; Adding cobalt phosphide microspheres into the suspension and stirring evenly to form an electrospinning solution; The electrospinning liquid is subjected to electrostatic spinning and dried to obtain a cobalt phosphide and carbon fiber composite catalytic material.

[0007] Preferably, the mass ratio of cobalt chloride hexahydrate, sodium dihydrogen phosphate and surfactant is (2-4):1:(2-3).

[0008] Preferably, 5-10 mg of sodium dihydrogen phosphate is added to every 1 mL of deionized water.

[0009] Preferably, the surfactant is cetyltrimethylammonium bromide or polyvinylpyrrolidone.

[0010] Preferably, the drying temperature is 60-100° C.; the solvent heat treatment temperature is 150-200° C., and the holding time is 6-12 hours.

[0011] Preferably, the heat treatment conditions include: heating to 600-800° C. at a heating rate of 10-20° C. / min under a nitrogen atmosphere, and keeping the temperature for 2-5 hours; the flow rate of the nitrogen is 20-60 mL / min.

[0012] Preferably, the usage ratio of polyacrylonitrile, N, N-dimethylformamide and cobalt phosphide microspheres is (40-80) g:1 L: (20-40) g.

[0013] Preferably, the electrospinning conditions include: a spinning voltage of 15 to 18 kV, a syringe injection rate of 0.8 to 1.2 mL / h, and a receiving distance of 10 to 20 cm for collecting the electrospun fibers by the roller.

[0014] The invention also discloses a cobalt phosphide and carbon fiber composite catalytic material, comprising carbon fiber and cobalt phosphide microspheres loaded on the carbon fiber; the carbon fiber is polyacrylonitrile fiber.

[0015] Preferably, in the cobalt phosphide and carbon fiber composite catalytic material, the mass ratio of cobalt phosphide microspheres to carbon fibers is (20%-40%): (60%-80%).

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing a cobalt phosphide and carbon fiber composite catalytic material. Through step-by-step compounding and structural regulation, a stable composite system of cobalt phosphide microspheres and carbon fibers is constructed. Uniformly dispersed cobalt phosphide microspheres are formed under solvent thermal conditions through the synergistic effect of cobalt chloride hexahydrate, sodium dihydrogen phosphate, and a surfactant. The surfactant can regulate the microsphere morphology and prevent agglomeration. Sodium dihydrogen phosphate acts as a phosphorus source and reacts with a cobalt salt to form a cobalt phosphide crystal structure. Polyacrylonitrile is dissolved in N,N-dimethylformamide to form a suspension with good spinnability, providing a continuous phase matrix for subsequent electrostatic spinning. The cobalt phosphide microspheres are dispersed in the suspension, and the active components are uniformly distributed in the fiber precursor through physical mixing. Finally, the composite solution is processed into a fiber structure through electrostatic spinning technology, and after drying, a composite catalytic material of carbon fiber-loaded cobalt phosphide microspheres is formed. The carbon fibers are formed by high-temperature carbonization of polyacrylonitrile, which not only provides a conductive network but also enhances mechanical stability. The cobalt phosphide microspheres are evenly anchored on the fiber surface as active sites, forming a three-dimensional catalytic interface with a high specific surface area. Cobalt phosphide microspheres are synthesized by solvent thermal reaction and uniformly loaded on a carbon fiber carrier in combination with electrostatic spinning technology, achieving efficient dispersion and stable combination of active components, while utilizing the high conductivity of carbon fiber to improve overall catalytic performance, with the advantages of improving the dispersibility of active components of catalytic materials, enhancing conductivity and structural stability. The raw materials and solvents used in the entire preparation process of the present invention are relatively environmentally friendly, and the waste generated in the preparation process is less, in line with the development trend of green chemistry, and conducive to reducing environmental pollution; the preparation method is simple, the production cost is low, the subsequent treatment is simple and does not require complex synthesis equipment, which is conducive to realizing the commercial application of water electrolysis hydrogen production technology.

[0017] Furthermore, the mass ratio of cobalt chloride hexahydrate and sodium dihydrogen phosphate controls the molar ratio of metal to phosphorus, preventing excessive metal salts from causing excessive crystal growth and forming irregular particles. The surfactant forms a micellar structure during the solvothermal process, guiding the metal salt to crystallize in a confined space and inhibiting particle agglomeration. Under the synergistic effect of the three, the metal salt gradually completes hydrolysis, condensation and phosphating reactions within the micelle template, ultimately forming a spherical structure of uniform size. If the surfactant ratio is too high, the micelle size will be too large, affecting the dispersibility of the microspheres; if the ratio is too low, the crystal growth direction cannot be effectively controlled.

[0018] Furthermore, the addition amount of sodium dihydrogen phosphate is 5–10 mg per 1 mL of deionized water. This concentration range ensures an optimal molar ratio of phosphorus to cobalt ions. When the concentration is below the lower limit, insufficient phosphorus source supply leads to incomplete cobalt phosphide formation, resulting in the appearance of unreacted cobalt oxide on the microsphere surface. When the concentration is above the upper limit, excess phosphate ions react with cobalt ions to form non-target products. By controlling this concentration, the phosphating reaction kinetics reaches equilibrium, resulting in the formation of a uniform crystal structure and a concentrated particle size distribution in the cobalt phosphide microspheres, avoiding problems such as particle agglomeration or uneven crystallinity.

[0019] Furthermore, the surfactant is hexadecyltrimethylammonium bromide or polyvinylpyrrolidone. The surfactant is used to regulate the surface charge distribution of the microspheres. Hexadecyltrimethylammonium bromide is used to prevent the microspheres from agglomerating through electrostatic stabilization; the polyvinylpyrrolidone molecular chain is wrapped around the crystal surface through a spatial steric effect, and regulates the anisotropic growth of the crystal through physical adsorption, thereby promoting the uniform distribution of cobalt phosphide microspheres on the carbon fiber surface.

[0020] Furthermore, when the drying process is carried out between 60 and 100°C, residual organic solvents such as N,N-dimethylformamide are gradually evaporated, while preventing the breakage or crosslinking of polyacrylonitrile molecular chains due to excessive temperatures. When the solvent thermal treatment temperature is controlled between 150 and 200°C, the reactant ions in the hydrothermal system obtain sufficient activation energy for nucleation reactions. Setting a holding time of 6 to 12 hours ensures that the crystal growth process approaches thermodynamic equilibrium.

[0021] Furthermore, the inert protective effect of the nitrogen atmosphere prevents the oxidative decomposition of the cobalt phosphide microspheres during high-temperature treatment, maintaining the integrity of their crystal structure. By controlling the heating rate between 10 and 20°C / min, the polyacrylonitrile fiber gradually removes non-carbon elements during the carbonization process, forming a carbon fiber structure with a continuous conductive network, while avoiding the agglomeration of the cobalt phosphide microspheres or the collapse of the carrier structure caused by a sudden temperature rise. Within the temperature range of 600 to 800°C, the polyacrylonitrile fiber completes carbonization and transforms into highly conductive carbon fibers. At the same time, chemical bonds are formed between the cobalt phosphide microspheres and the carbon fibers through interfacial diffusion. Holding the temperature for 2 to 5 hours increases the crystallinity of the carbon fibers, stabilizes the cobalt phosphide crystal phase, and strengthens the interfacial bonding strength between the two. Controlling the nitrogen flow rate within the range of 20 to 60 mL / min can not only effectively replace residual oxygen in the reaction system, but also avoid uneven heat distribution caused by airflow disturbances.

[0022] Furthermore, when the concentration of polyacrylonitrile is controlled at 40~80g / L, the viscosity of the spinning solution is moderate, and a continuous and uniform diameter fiber structure can be formed by electrospinning. When cobalt phosphide microspheres are dispersed in the spinning solution at a ratio of 20~40g / L, the microspheres are evenly distributed inside and on the surface of the fiber, forming a stable composite structure. N,N-dimethylformamide is used as a solvent, and its dosage is fixed at 1L, which matches the solubility characteristics of polyacrylonitrile, ensuring that the spinning solution maintains stable rheological properties during the electrospinning process. Through the synergistic effect of the three, a close bond is formed between the active component and the carbon fiber carrier, while maintaining the continuity of the conductive network of the fiber.

[0023] Furthermore, when the spinning voltage is set to 15~18kV, the electric field strength can not only overcome the surface tension of the solution to form a continuous jet, but also avoid excessive voltage causing jet breakage or excessively wide fiber diameter distribution. The syringe push rate is controlled in the range of 0.8~1.2mL / h to match the solution extrusion rate with the electric field stretching rate, preventing the fiber diameter from coarsening due to excessive flow rate or jet discontinuity caused by too slow flow rate. When the receiving distance is set to 10~20cm, the jet completes full stretching and solvent volatilization during flight, while ensuring that the fibers form an orderly arranged structure on the drum surface. Under the synergistic effect of the three, cobalt phosphide microspheres can be evenly embedded in the fiber to form a composite fiber substrate with a three-dimensional conductive network.

[0024] The present invention also discloses a cobalt phosphide and carbon fiber composite catalytic material. The polyacrylonitrile fiber is carbonized to form a three-dimensional network structure. Its graphitized carbon skeleton chemically bonds with cobalt phosphide microspheres through π-π conjugation, inhibiting the leaching of active components in acidic environments. The cobalt phosphide microspheres are evenly loaded on the surface of the carbon fiber, forming a continuous conductive path. The interfacial coupling between the microspheres and the fiber reduces the charge transfer impedance. The polyacrylonitrile fiber precursor forms a mesoporous structure during high-temperature treatment. This structure effectively anchors the cobalt phosphide microspheres, preventing particle agglomeration or shedding during the reaction. This solves the problem of non-precious metal catalysts being easily deactivated in acidic environments. The conductive network of the carbon fiber reduces the charge transfer impedance, and the uniform loading of the cobalt phosphide microspheres increases the effective catalytic sites. The three-dimensional structure formed by the carbonization of the polyacrylonitrile fiber fixes the active components through the dual effects of physical confinement and chemical bonding, preventing structural collapse during the reaction. The interfacial coupling between the microspheres and the fiber optimizes the electron transmission path and improves the kinetics of the oxygen evolution reaction.

[0025] Furthermore, when the mass proportion of cobalt phosphide microspheres is controlled in the range of 20%-40%, the microspheres can be evenly dispersed on the carbon fiber surface without agglomeration, which not only ensures sufficient exposure area of ​​active sites but also avoids excessive loading that causes clogging of the carrier pores. When the mass proportion of carbon fiber is maintained in the range of 60%-80%, the fiber network can form a continuous conductive path and provide sufficient support area for the dispersion of microspheres. This ratio forms an effective electron transmission channel at the interface between microspheres and fibers by regulating the spatial distribution relationship between the active components and the carrier, so that the catalytic activity and conductive performance are synergistically optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention discloses a flow chart of the preparation method of the cobalt phosphide and carbon fiber composite catalytic material. DETAILED DESCRIPTION

[0027] The technical solution of the present invention will be described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0029] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0030] In the present invention, unless otherwise specified, percentages (%) or parts refer to percentages by weight or parts by weight relative to the composition.

[0031] In the present invention, unless otherwise specified, the components involved or their preferred components can be combined with each other to form a new technical solution.

[0032] In this disclosure, unless otherwise specified, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "6-22" indicates that all real numbers between "6-22" are listed herein, and "6-22" is merely an abbreviation for these numerical combinations.

[0033] The "range" disclosed in the present invention is in the form of lower limit and upper limit, which can be one or more lower limits, and one or more upper limits respectively.

[0034] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0035] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the order. Preferably, the reaction method herein is carried out sequentially.

[0036] Unless otherwise indicated, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0037] The present invention discloses a method for preparing a cobalt phosphide and carbon fiber composite catalytic material, comprising the following steps: Dissolve cobalt chloride hexahydrate, sodium dihydrogen phosphate and surfactant in deionized water and stir evenly; The mixture was transferred into an autoclave and placed in an oven for solvothermal treatment; After cooling to room temperature, the precipitate was filtered out, washed with deionized water and ethanol several times, and then dried in an oven at 60–100 °C; The mixture is placed in a crucible and heat-treated in a muffle furnace to obtain cobalt phosphide microspheres; Dissolve polyacrylonitrile in N, N-dimethylformamide to obtain a uniform suspension; Adding cobalt phosphide microspheres to the above suspension and stirring evenly to form an electrospinning solution; electrospinning the electrospinning solution; The mixture is dried in a drying oven at 60-100° C. to obtain a cobalt phosphide and carbon fiber composite catalytic material.

[0038] By dissolving cobalt chloride hexahydrate, sodium dihydrogen phosphate and surfactant in deionized water, and preparing cobalt phosphide microspheres through high-pressure reactor treatment, heat treatment and other steps, the active components are evenly dispersed in the carbon carrier, forming a stable composite structure, and effectively solving the problem of traditional non-precious metal catalysts being easily deactivated in acidic environments; polyacrylonitrile fiber has excellent conductivity and a large specific surface area. Using polyacrylonitrile fiber as a carbon carrier, combined with the loading of cobalt phosphide microspheres, not only improves the conductivity of the catalytic material, but also provides more catalytic active sites, helps to form a stable catalytic structure, and significantly improves the electrocatalytic performance.

[0039] As a further improvement of the present invention, the mass ratio of cobalt chloride hexahydrate to sodium dihydrogen phosphate is 2:1 to 4:1. Cobalt chloride hexahydrate, acting as a cobalt source, participates in the phosphating reaction to form a cobalt phosphide crystal structure. Specifically, this can be achieved by using a mass ratio of 2 to 4 times that of sodium dihydrogen phosphate. This ratio ensures that the metal precursor fully participates in the reaction. Sodium dihydrogen phosphate, acting as a phosphorus source, maintains a phosphorus supply. Specifically, this is achieved by using a base mass ratio of 1, which ensures stable release of phosphorus during the phosphating reaction.

[0040] As a further improvement of the present invention, the surfactants are cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP). The surfactant is used to control the surface charge distribution of the microspheres. Cetyltrimethylammonium bromide can be used to prevent microsphere agglomeration through electrostatic stabilization. Cetyltrimethylammonium bromide is a cationic surfactant, specifically a quaternary ammonium salt structure containing a long-chain alkyl group. Its hydrophilic end electrostatically adsorbs onto the metal ion surface to form a micelle template, while its hydrophobic end controls the direction of crystal growth through intermolecular forces. This characteristic forms a stable micelle structure, guiding the cobalt phosphide microspheres to form a uniform spherical morphology while suppressing interparticle agglomeration. During the synthesis of the cobalt phosphide microspheres, cetyltrimethylammonium bromide forms an aligned micelle structure through electrostatic attraction between the cationic groups and the metal coordination ions. These micelles act as soft templates, guiding the directional binding of phosphate ions and cobalt ions within a confined space, forming uniformly sized spherical cobalt phosphide particles. Polyvinyl pyrrolidone forms coordination bonds with metal ions through the carbonyl groups in its molecular chain, wrapping the particle surface during crystal growth and effectively inhibiting irregular morphology caused by excessive crystal face growth. The two surfactants synergistically control the crystallization process of cobalt phosphide microspheres through charge interaction and steric hindrance mechanism, respectively, to form a porous structure with a high specific surface area, thus achieving monodisperse loading of cobalt phosphide microspheres in the carbon fiber carrier. Polyacrylonitrile dissolves to form a viscoelastic solution, which serves as the continuous phase matrix for electrospinning and is converted into conductive carbon fibers during the subsequent carbonization process. Electrospinning forms continuous fibers from a polymer solution through the action of a high-voltage electric field. Specifically, a voltage of 15-18kV is used to stretch and solidify the electrospinning liquid jet to form a fiber structure loaded with microspheres.

[0041] As a further improvement of the present invention, the mass ratio of sodium dihydrogen phosphate to surfactant is 1:2 to 1:3. The surfactant regulates the growth morphology of the microspheres through molecular self-assembly. Specifically, this can be achieved using hexadecyltrimethylammonium bromide or polyvinylpyrrolidone. When the mass ratio of cetyltrimethylammonium bromide or polyvinylpyrrolidone is 2 to 3 times that of the phosphorus source, micelle templates can be effectively formed. This solves the problem of insufficient dispersibility of the active component during the preparation of cobalt phosphide microspheres. The micelle template formed by the surfactant enables uniform distribution and directional crystallization of the metal salt. The improved stability of the microsphere structure is due to the spatial restriction effect of the micelle on crystal growth, avoiding crystal defects caused by excessive local concentration. The uniform distribution of catalytic active sites is achieved through the uniform size of the spherical structure. After optimizing the surfactant ratio, the specific surface area of ​​the microspheres is significantly increased, exposing more active sites.

[0042] As a further improvement to the present invention, the ratio of sodium dihydrogen phosphate to deionized water is (5-10) mg:1 mL. Sodium dihydrogen phosphate serves as a phosphorus source in the synthesis reaction of cobalt phosphide microspheres, and mass concentration control is employed to regulate the phosphorus supply in the reaction system. Deionized water serves as a solvent to dissolve the reactants and maintain the ionic strength of the reaction system. Precise regulation of reactant concentration is achieved by controlling the ratio of solvent volume to solute mass. This effectively addresses the problems of particle agglomeration and incomplete reaction caused by improper phosphorus source concentration control, resulting in cobalt phosphide microspheres with a uniform crystal structure and stable particle size distribution. This control method ensures high dispersion of the active components on the carbon fiber support, thereby increasing the active site density and structural stability of the catalytic material, laying the foundation for subsequent optimization of electrocatalytic performance.

[0043] As a further improvement to the present invention, the solvent thermal treatment temperature is 150-200°C and the temperature is maintained for 6-12 hours. This effectively controls the thermal stress distribution during the precursor drying process, avoiding fiber structure collapse and microsphere agglomeration, and uniformly dispersing the cobalt phosphide microspheres on the surface of the carbon fiber support. Optimizing the solvent thermal treatment conditions ensures the complete development of cobalt phosphide crystals, forming active components with regular morphology and high specific surface area, providing a stable three-phase interface and sufficient active sites for the electrocatalytic reaction.

[0044] As a further improvement to the present invention, the heat treatment conditions are as follows: heating to 600-800°C at a heating rate of 10-20°C / min under a nitrogen atmosphere and maintaining the temperature for 2-5 hours; the nitrogen flow rate is 20-60 mL / min. This effectively avoids oxidative decomposition of the cobalt phosphide microspheres during high-temperature treatment, maintaining the stability of the catalytic active sites; promotes the formation of a strong interfacial bond between the carbon fibers and the cobalt phosphide microspheres, and enhances electron transfer efficiency. By optimizing the combination of heat treatment parameters, the durability of the catalytic material in acidic environments is significantly improved while maintaining the structural integrity of the material.

[0045] As a further improvement of the present invention, the ratio of polyacrylonitrile and N, N-dimethylformamide is (40~80)g:1L.

[0046] As a further improvement to the present invention, the ratio of cobalt phosphide microspheres to N,N-dimethylformamide is (20-40) g:1 L. This solves the problem of poor dispersibility and stability of the active component in the carbon support, while achieving a balance between catalytic performance and conductivity. The active component is evenly dispersed in the fiber matrix, forming a stable composite structure, avoiding the decline in catalytic activity caused by microsphere agglomeration. The continuous conductive network of carbon fibers provides an efficient electron transport path for the electrocatalytic reaction, thereby improving the overall performance of the catalytic material.

[0047] As a further improvement to the present invention, the spinning voltage is 15-18 kV, the syringe injection rate is 0.8-1.2 mL / h, and the receiving distance of the roller collecting the electrospun fibers is 10-20 cm. This significantly improves the diameter uniformity and surface smoothness of the electrospun fibers, allowing the cobalt phosphide microspheres to be monodispersed within the fiber matrix. The regular arrangement of the fiber's three-dimensional network structure enhances electron transfer efficiency, while the increased interfacial bonding strength between the microspheres and the fibers effectively prevents the catalytically active components from falling off during the reaction.

[0048] Cobalt chloride hexahydrate and sodium dihydrogen phosphate undergo a phosphating reaction under solvothermal conditions to form CoP crystals. Surfactants control the crystal growth size and morphology through steric hindrance. The resulting cobalt phosphide microspheres undergo high-temperature heat treatment, increasing their crystallinity and forming a stable passivation layer on their surface, enhancing acid corrosion resistance. A polyacrylonitrile solution, serving as a fiber precursor, is mixed with the cobalt phosphide microspheres to form a uniform dispersion. During electrospinning, the microspheres are encapsulated within the fibers or attached to the surface, forming a three-dimensional network structure after drying. During carbonization, the polyacrylonitrile is converted into graphitized carbon fibers, forming a strong interfacial bond with the cobalt phosphide microspheres and constructing a continuous electron transport channel. This application effectively prevents the dissolution and inactivation of cobalt phosphide in acidic media. The carbon fiber network provides a rapid electron transport pathway for the catalytic reaction, and the interfacial bonding between the microspheres and the fibers enhances structural stability. The uniform distribution of active components within the fiber matrix exposes more catalytically active sites, and the three-dimensional porous structure facilitates reactant mass transfer, significantly improving the efficiency of the oxygen evolution reaction and the stability of the catalytic cycle.

[0049] The present invention provides a cobalt phosphide and carbon fiber composite catalytic material, comprising cobalt phosphide microspheres and carbon fibers, wherein the carbon fibers are polyacrylonitrile fibers, and the cobalt phosphide microspheres are loaded on the carbon fibers; the mass ratio of the cobalt phosphide microspheres to the carbon fibers is (20%-40%):(60%-80%).

[0050] Figure 1The flow chart of the preparation method of the cobalt phosphide and carbon fiber composite catalytic material disclosed in the present invention is as follows. The preparation method of the cobalt phosphide and carbon fiber composite catalytic material disclosed in the present invention comprises the following steps: dissolving cobalt chloride hexahydrate, sodium dihydrogen phosphate, and a surfactant in deionized water, stirring uniformly, and solvent-thermally treating the solution, followed by washing, drying, and heat treatment to obtain cobalt phosphide microspheres; dissolving polyacrylonitrile in N,N-dimethylformamide to obtain a suspension; adding the cobalt phosphide microspheres to the suspension, stirring uniformly to form an electrospinning solution; and electrospinning the electrospinning solution and drying to obtain the cobalt phosphide and carbon fiber composite catalytic material. Cobalt phosphide loaded on carbon fiber significantly enhances electrocatalytic performance by combining the excellent catalytic properties of cobalt phosphide with the excellent conductivity of carbon fiber. Loading cobalt phosphide on carbon fiber increases the specific surface area of ​​the catalyst material, providing more catalytically active sites and facilitating the formation of a stable catalytic structure, thereby improving the reaction rate and efficiency of the electrocatalysis. By optimizing the mass ratio of cobalt phosphide to carbon fiber, the catalytic performance and conductivity can be further balanced to achieve the optimal catalytic effect. This helps ensure sufficient catalytic sites while also providing a good electron transfer path. Furthermore, the raw materials and solvents used throughout the preparation process of the present invention are relatively environmentally friendly, and the preparation process generates relatively little waste. This helps reduce environmental pollution and conforms to the development trend of green chemistry. The preparation method of the present invention is simple, has low production costs, is easy to process, and does not require complex synthesis equipment.

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0052] Example 1 A method for preparing a cobalt phosphide and carbon fiber composite catalytic material comprises the following steps: Step 1: Dissolve 0.2 g of cobalt chloride hexahydrate, 0.1 g of sodium dihydrogen phosphate, and 0.2 g of CTAB in 10 mL of deionized water, stir well, transfer to an autoclave, and place in an oven. Gradually increase the temperature to 150°C and keep warm for 12 h. Step 2: After the mixture is cooled to room temperature, the precipitate is filtered out and washed with deionized water and ethanol several times. After washing, it is dried in an oven at 60°C. The mixture is then placed in a crucible and heated to 600°C in a muffle furnace at a heating rate of 10°C / min. The temperature is kept at this temperature for 5 hours with a nitrogen flow rate of 20 mL / min to obtain cobalt phosphide microspheres. Step 3: Dissolve 0.2g of polyacrylonitrile in 5mL of N, N-dimethylformamide to obtain a uniform suspension; add 0.1g of cobalt phosphide microspheres to the above suspension and stir evenly to form an electrospinning solution. The electrospinning solution is electrospun at a spinning voltage of 15kV and a syringe injection rate of 0.8mL / h. The receiving distance of the roller to collect the electrospun fiber is 10cm, and the material is dried in a drying oven at 60°C to obtain the final composite catalytic material.

[0053] Among them, the mass of cobalt phosphide is 33% of the cobalt phosphide and carbon fiber composite catalytic material, and the mass of carbon fiber is 67% of the cobalt phosphide and carbon fiber composite catalytic material.

[0054] Example 2 A method for preparing a cobalt phosphide and carbon fiber composite catalytic material comprises the following steps: Step 1: Dissolve 0.4 g of cobalt chloride hexahydrate, 0.1 g of sodium dihydrogen phosphate, and 0.3 g of PVP in 20 mL of deionized water, stir evenly, transfer to a high-pressure reactor, and place in an oven. Gradually increase the temperature to 200 ° C and keep warm for 6 hours. Step 2: After the mixture is cooled to room temperature, the precipitate is filtered out and washed with deionized water and ethanol several times. After washing, it is dried in an oven at 100°C. The mixture is then placed in a crucible and heated to 800°C in a muffle furnace at a heating rate of 20°C / min and kept at this temperature for 2 hours. The nitrogen flow rate is 60 mL / min to obtain cobalt phosphide microspheres. Step 3: Dissolve 0.4 g of polyacrylonitrile in 5 mL of N, N-dimethylformamide to obtain a uniform suspension; add 0.17 g of cobalt phosphide microspheres to the above suspension and stir evenly to form an electrospinning solution. The electrospinning solution is electrospun at a spinning voltage of 18 kV and a syringe injection rate of 1.2 mL / h. The receiving distance of the electrospun fiber collected by the roller is 20 cm, and the solution is dried in a drying oven at 100°C to obtain the final composite catalytic material.

[0055] The mass of cobalt phosphide accounts for 30% of the composite catalytic material of cobalt phosphide and carbon fiber, and the mass of carbon fiber accounts for 70% of the composite catalytic material of cobalt phosphide and carbon fiber.

[0056] Example 3 A method for preparing a cobalt phosphide and carbon fiber composite catalytic material comprises the following steps: Step 1: Dissolve 0.3 g of cobalt chloride hexahydrate, 0.1 g of sodium dihydrogen phosphate, and 0.3 g of CTAB in 20 mL of deionized water, stir well, transfer to an autoclave, and place in an oven. Gradually increase the temperature to 180°C and keep warm for 8 h. Step 2: After the mixture is cooled to room temperature, the precipitate is filtered out and washed with deionized water and ethanol several times. After washing, it is dried in an oven at 80°C. The mixture is then placed in a crucible and heated to 700°C in a muffle furnace at a heating rate of 15°C / min. The temperature is kept at this temperature for 3 hours with a nitrogen flow rate of 30 mL / min to obtain cobalt phosphide microspheres. Step 3: Dissolve 0.25g of polyacrylonitrile in 5mL of N, N-dimethylformamide to obtain a uniform suspension; add 0.15g of cobalt phosphide microspheres to the above suspension and stir evenly to form an electrospinning solution. The electrospinning solution is electrospun at a spinning voltage of 16kV and a syringe injection rate of 1mL / h. The receiving distance of the roller to collect the electrospun fiber is 15cm, and the material is dried in a drying oven at 80°C to obtain the final composite catalytic material.

[0057] Among them, the mass of cobalt phosphide is 37% of the cobalt phosphide and carbon fiber composite catalytic material, and the mass of carbon fiber is 63% of the cobalt phosphide and carbon fiber composite catalytic material.

[0058] Example 4 A method for preparing a cobalt phosphide and carbon fiber composite catalytic material comprises the following steps: Step 1: Dissolve 0.25 g of cobalt chloride hexahydrate, 0.1 g of sodium dihydrogen phosphate, and 0.2 g of PVP in 15 mL of deionized water, stir well, transfer to an autoclave, and place in an oven. Gradually increase the temperature to 160°C and keep warm for 10 h. Step 2: After the mixture is cooled to room temperature, the precipitate is filtered out and washed with deionized water and ethanol several times. After washing, it is dried in an oven at 80°C. The mixture is then placed in a crucible and heated to 600°C in a muffle furnace at a heating rate of 20°C / min and kept at this temperature for 4 hours. The nitrogen flow rate is 30 mL / min to obtain cobalt phosphide microspheres. Step 3: Dissolve 0.3 g of polyacrylonitrile in 5 mL of N, N-dimethylformamide to obtain a uniform suspension; add 0.2 g of cobalt phosphide microspheres to the above suspension and stir evenly to form an electrospinning solution. The electrospinning solution is electrospun at a spinning voltage of 17 kV and a syringe injection rate of 1 mL / h. The receiving distance of the roller to collect the electrospun fiber is 15 cm, and the material is dried in a drying oven at 80°C to obtain the final composite catalytic material.

[0059] Among them, the mass of cobalt phosphide is 40% of the cobalt phosphide and carbon fiber composite catalytic material, and the mass of carbon fiber is 60% of the cobalt phosphide and carbon fiber composite catalytic material.

[0060] Example 5 A method for preparing a cobalt phosphide and carbon fiber composite catalytic material comprises the following steps: Step 1: Dissolve 0.35 g of cobalt chloride hexahydrate, 0.1 g of sodium dihydrogen phosphate, and 0.25 g of CTAB in 18 mL of deionized water, stir well, transfer to an autoclave, and place in an oven. Gradually increase the temperature to 180°C and keep warm for 8 h. Step 2: After the mixture is cooled to room temperature, the precipitate is filtered out and washed with deionized water and ethanol several times. After washing, it is dried in an oven at 70°C. The mixture is then placed in a crucible and heated to 800°C in a muffle furnace at a heating rate of 20°C / min and kept at this temperature for 3.5 hours. The nitrogen flow rate is 40 mL / min to obtain cobalt phosphide microspheres. Step 3: Dissolve 0.4 g of polyacrylonitrile in 5 mL of N, N-dimethylformamide to obtain a uniform suspension; add 0.1 g of cobalt phosphide microspheres to the above suspension and stir evenly to form an electrospinning solution. The electrospinning solution is electrospun at a spinning voltage of 17 kV and a syringe injection rate of 1 mL / h. The receiving distance of the roller to collect the electrospun fiber is 15 cm, and the material is dried in a drying oven at 70°C to obtain the final composite catalytic material.

[0061] The mass of cobalt phosphide accounts for 20% of the composite catalytic material of cobalt phosphide and carbon fiber, and the mass of carbon fiber accounts for 80% of the composite catalytic material of cobalt phosphide and carbon fiber.

[0062] In summary, the present invention provides a cobalt phosphide and carbon fiber composite catalytic material and a preparation method thereof. The cobalt phosphide and carbon fiber composite catalytic material comprises cobalt phosphide microspheres and carbon fibers, wherein the carbon fibers are polyacrylonitrile fibers, and the cobalt phosphide microspheres are supported on the carbon fibers. The preparation method comprises: preparing the cobalt phosphide microspheres by a solvothermal method, mixing the cobalt phosphide microspheres with an organic solution of polyacrylonitrile, and preparing the carbon fiber-supported cobalt phosphide microsphere composite catalytic material by electrospinning. The carbon fiber-supported cobalt phosphide microsphere composite material prepared by the present invention has a stable structure, a simple preparation process, and excellent electrocatalytic performance, making it suitable for industrial large-scale production.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a cobalt phosphide and carbon fiber composite catalytic material, characterized in that: The following steps are involved: Cobalt chloride hexahydrate, sodium dihydrogen phosphate and a surfactant are dissolved in deionized water, stirred evenly, subjected to solvent heat treatment, and then washed, dried and heat treated to obtain cobalt phosphide microspheres; dissolving polyacrylonitrile in N, N-dimethylformamide to obtain a suspension; Adding cobalt phosphide microspheres into the suspension and stirring evenly to form an electrospinning solution; The electrospinning liquid is subjected to electrostatic spinning and dried to obtain a cobalt phosphide and carbon fiber composite catalytic material.

2. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: The mass ratio of the cobalt chloride hexahydrate, sodium dihydrogen phosphate and surfactant is (2-4):1:(2-3).

3. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: Add 5-10 mg of sodium dihydrogen phosphate per 1 mL of deionized water.

4. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: The surfactant is cetyltrimethylammonium bromide or polyvinylpyrrolidone.

5. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: The drying temperature is 60-100° C.; the solvent heat treatment temperature is 150-200° C., and the heat preservation time is 6-12 hours.

6. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: The heat treatment conditions include: heating to 600-800° C. at a heating rate of 10-20° C. / min under a nitrogen atmosphere, and keeping the temperature for 2-5 hours; the flow rate of the nitrogen is 20-60 mL / min.

7. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: The usage ratio of the polyacrylonitrile, N, N-dimethylformamide and cobalt phosphide microspheres is (40-80) g:1 L: (20-40) g.

8. The method for preparing a cobalt phosphide and carbon fiber composite catalytic material according to claim 1, characterized in that: The electrospinning conditions include: a spinning voltage of 15-18 kV, a syringe injection rate of 0.8-1.2 mL / h, and a receiving distance of 10-20 cm for collecting the electrospun fibers by a roller.

9. A cobalt phosphide and carbon fiber composite catalytic material, characterized in that: The invention comprises carbon fibers and cobalt phosphide microspheres loaded on the carbon fibers; the carbon fibers are polyacrylonitrile fibers.

10. The cobalt phosphide and carbon fiber composite catalytic material according to claim 9, characterized in that: In the cobalt phosphide and carbon fiber composite catalytic material, the mass ratio of cobalt phosphide microspheres to carbon fibers is (20%-40%): (60%-80%).

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