Laminar mesoporous carbon supports and their preparation methods, platinum-based catalyst preparation methods and applications

Abstract

This invention discloses a layered mesoporous carbon support and a platinum-based catalyst, as well as their preparation methods and applications, belonging to the field of electrocatalysis and fuel cell technology. The support possesses a unique two-dimensional layered morphology and a uniformly sized mesoporous network, with nitrogen-doped functional groups on its surface. The average pore size is 2-10 nm, and the BET specific surface area is 500-2000 m². 2 / g. The preparation method includes: mixing a carbon source, a structure-directing agent, and a layered regulator in an alcohol-water solution; inducing self-assembly through solvent evaporation to form a layered precursor gel; and then obtaining the support through stepwise carbonization. High-performance platinum-based catalysts can be prepared by loading platinum nanoparticles onto the above support. This support structure effectively improves mass transfer and conductivity, enhances the interaction with active components, and solves the problems of easy corrosion and platinum particle agglomeration in traditional catalyst supports. The catalyst prepared from it exhibits excellent activity and stability in the oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis and fuel cell technology, specifically relating to a sheet-like mesoporous carbon support, a method for preparing the carbon support, a method for preparing a platinum-based catalyst using the carbon support, and its application in the oxygen reduction reaction (ORR). Background Technology

[0002] The oxygen reduction reaction (ORR) is a critical reaction at the cathode of a fuel cell, and its extremely slow kinetics make it a major bottleneck limiting the overall performance and energy conversion efficiency of the fuel cell. Currently, platinum-based catalysts (Pt / C) remain the most commonly used cathode catalysts in commercial fuel cells due to their excellent intrinsic activity and good reaction selectivity for ORR. However, traditional Pt / C catalysts still suffer from the following key problems: First, Pt nanoparticles are prone to agglomeration and dissolution during operation. Under acidic electrolyte and high-potential cycling conditions, Pt particles gradually migrate, dissolve, or sinter, leading to a decrease in catalyst activity. The main reason for this is that traditional carbon supports (such as Vulcan XC-72 or Ketjen Black) have limited conductivity and high surface chemical inertness, making it difficult to form a stable interfacial bond with Pt particles. Second, the corrosion problem of carbon supports is severe. During long-term operation, carbon supports are easily corroded under high-potential and oxidizing environments, leading to the shedding of active components, pore blockage, and electrode performance degradation. Especially under start-up-stop or dynamic load conditions, support corrosion becomes one of the main mechanisms of Pt / C system failure.

[0003] In recent years, researchers have proposed various improvement strategies, such as novel carbon supports including carbon nanotubes, graphene, carbon nanofibers, and porous carbon. These materials improve the dispersibility and anti-sintering ability of Pt by adjusting the structure and chemical environment. However, these carbon materials still face some technical bottlenecks: simple pore structures limit mass transfer. Most porous carbons have microporous or disordered mesoporous structures with uneven pore size distribution and long gas diffusion paths, resulting in low transport efficiency of ORR reactants (O2) and products (H2O); insufficient exposure of active sites, with Pt particles often embedded inside the carbon pores, making it difficult to fully contact reactant gases and reducing practical utilization; weak interaction between the support and Pt. The lack of functionalized sites on the carbon surface leads to easy migration and aggregation of Pt after calcination or long-term operation; discontinuous conductive networks. The diverse morphologies of carbon materials and poor contact between carbon layers or platinum particles hinder electron transport. To address these problems, constructing carbon supports with layered structures and mesoporous networks has become an effective design approach. The layered structure shortens the electron and gas diffusion paths, improving the utilization rate of the reaction interface; the mesoporous structure promotes the rapid transport of O2 molecules and the removal of product water, preventing local blockage. Furthermore, the surface of the layered mesoporous carbon can form Lewis basic sites through doping with nitrogen, oxygen, and other heteroatoms, enhancing the interaction between Pt and the support and improving the structural stability of the catalyst. Summary of the Invention

[0004] The purpose of this invention is to provide a layered mesoporous carbon support with controllable layered structure and uniform mesoporous system, significantly improving the mass transfer capacity and corrosion resistance of the support, and its preparation method. Furthermore, it provides a method for preparing highly active and durable layered mesoporous carbon-platinum-based fuel cell catalysts using this carbon support, thereby addressing the problems of easy corrosion of carbon supports, easy migration and aggregation of platinum particles, structural instability, and limited mass transfer capacity in existing Pt / C catalysts. This invention achieves high dispersion, high activity, and high stability of platinum nanoparticles by constructing a controllable layered mesoporous carbon support, thus significantly improving the catalytic performance of the oxygen reduction reaction (ORR).

[0005] To achieve the above objectives, the present invention adopts the following technical solution: 1. A method for preparing a layered mesoporous carbon support, characterized by comprising the following steps: S1. Precursor solution construction and directional self-assembly: A carbon source, a structure directing agent, and a layering regulator are dissolved in a mixed solution of alcohol and water to form a homogeneous and transparent precursor solution; wherein the carbon source is a nitrogen-containing carbon source, and the layering regulator is selected from one or more of urea, ammonia, or triethanolamine. S2. Formation of sheet gel: The precursor solution obtained in step S1 is subjected to solvent evaporation to induce self-assembly or sol-gel reaction, so that the carbon source and template molecules are oriented in two dimensions to form a sheet-like organic-inorganic composite gel, which is then dried to obtain a solid precursor; S3. Stepwise carbonization and template removal of mesoporous carbon support: The solid precursor obtained in step S2 is subjected to stepwise heat treatment under an inert atmosphere: First, pre-carbonization is carried out at 400-500 ℃ to allow the template to decompose and volatilize, while fixing the lamellar morphology and reducing damage caused by volume shrinkage; then, high-temperature carbonization is carried out at 800-900 ℃ to enhance the graphitization degree of the carbon skeleton, improve conductivity, and achieve in-situ doping of nitrogen, ultimately forming a lamellar mesoporous carbon support with a two-dimensional lamellar morphology, uniform pore size, and nitrogen-doped functional groups on the surface.

[0006] The pre-carbonization stage is the framework stiffening period, during which the template agent begins to degrade, but the carbon source is not yet fully graphitized. Stepwise heating allows pyrolysis gases to slowly permeate out, avoiding sheet peeling or pore wall collapse caused by a sudden increase in gas pressure due to instantaneous high temperature. The high-temperature carbonization stage is the conductivity building period, during which graphitization is carried out within the already stable mesoporous framework, improving the conductivity and chemical stability of the carrier and forming a sheet-like mesoporous carbon carrier with a regular mesoporous structure.

[0007] More preferably, the structure-directing agent in step S1 is selected from one or more of block copolymers F127, P123, or cationic surfactant CTAB, with block copolymer F127 being the preferred choice. It can form stable micelles in an alcohol-water system and induce the carbon source to construct a uniformly sized mesoporous network. During the construction of lamellar mesoporous carbon, the structure-directing agent mainly forms a scale-controllable micelle structure through self-assembly in an alcohol-water mixed solution. During solvent evaporation-induced self-assembly or sol-gel processes, it acts as a nanoscale "soft template," guiding carbon source molecules to orderly accumulate and solidify around it or in the micelle gaps. This results in the transformation into uniformly sized, interconnected mesoporous channels after subsequent carbonization and template removal. The type and amount of the structure-directing agent directly determine the pore size, channel distribution, and degree of order of the mesopores.

[0008] More preferably, the layered regulator is selected from one or more mixtures of urea and ammonia. The layered regulator does not directly participate in the template construction of mesopore size, but rather finely regulates the polymerization kinetics and self-assembly behavior of the carbon source precursor by adjusting the pH, ionic strength, and intermolecular interactions of the system. This inhibits disordered three-dimensional cross-linking growth and promotes the directional expansion and stacking of the precursor along the two-dimensional direction, thereby achieving the formation and thickness adjustment of the lamellar morphology.

[0009] More preferably, the carbon source is one or a mixture of dopamine, resorcinol, phenolic resin, melamine, glucose, or polyaniline, with dopamine being the preferred choice. The nitrogen-containing carbon source and the nitrogen-containing layered control agent work synergistically during self-assembly and carbonization to achieve uniform, stable, and controllable nitrogen doping.

[0010] More preferably, the alcohol is one or a mixture of methanol, ethanol, isopropanol or ethylene glycol.

[0011] More preferably, in step S3, the pre-carbonization temperature is 400-500 °C, and the heating rate is 1-5 °C·min. -1 The holding time is 1-3 hours; the high-temperature carbonization temperature is 800-900 ℃, and the heating rate is 1-5 ℃·min. -1 The heat preservation time is 1-3 hours.

[0012] More preferably, in step S2, the drying temperature is 60-80 ℃, and the drying is carried out under vacuum or normal pressure for 6-12 hours.

[0013] More preferably, the volume ratio of alcohol to water in step S1 is 5:1 to 1:5; the alcohol-water mixture is mainly used to improve the formation of template agent micelles, regulate the solubility of carbon source, control the evaporation-induced self-assembly rate, and ensure the uniform growth of the lamellar structure.

[0014] More preferably, in step S2, the solvent evaporation-induced self-assembly or sol-gel reaction is carried out under constant temperature conditions; the temperature of the constant temperature conditions is 30-40 ℃, the relative humidity is 30-60%, and the holding time is 6-24 hours.

[0015] The second aspect of this invention discloses a layered mesoporous carbon support, prepared by the method described above. The layered mesoporous carbon support possesses a two-dimensional open morphology and a mesoporous network with uniform pore size, and its surface contains nitrogen-doped functional groups. The source of nitrogen in the nitrogen-doped functional groups depends on the synergistic effect of the selected carbon source and the layering regulator: when a nitrogen-containing carbon source is used, the carbon source is the main nitrogen donor; when the carbon source does not contain nitrogen, nitrogen-containing layering regulators such as urea, ammonia, or triethanolamine decompose during self-assembly and carbonization and are incorporated in situ into the carbon framework, becoming an important source of nitrogen doping. The synergy between the two can achieve uniform, stable, and controllable nitrogen doping while ensuring the integrity of the layered structure, thereby significantly enhancing the platinum-support interaction and the activity and durability of the catalyst.

[0016] More preferably, the layered mesoporous carbon support has an average pore size of 2 nm to 10 nm and a BET specific surface area of ​​500 m². 2 / g to 2000 m 2 / g.

[0017] The layered structure designed for use in proton exchange membrane fuel cells offers the following technical advantages: significantly shortening electron transport paths and reducing charge transfer resistance; constructing an open two-dimensional mass transfer network to improve oxygen diffusion efficiency; enhancing the surface exposure of Pt nanoparticles and improving Pt utilization; enhancing metal-support electronic coupling, regulating the Pt electronic structure, and improving ORR kinetics; increasing the graphitization degree of the carbon support and enhancing corrosion resistance; and improving water management performance and reducing mass transfer polarization. However, the pore size of mesoporous carbon supports is neither necessarily better the larger nor the smaller the better. When the pore size increases, more ionomers can penetrate into the mesoporous channels, leading to increased catalyst poisoning and disrupting the ionomer transport pathways on the outer surface of the carbon support. Specifically, while larger pore sizes are beneficial for oxygen transport, the adsorption of sulfonic acid groups on the platinum surface is significantly enhanced, resulting in decreased catalytic activity and increased proton transport resistance. Conversely, when the pore size is too small, a considerable proportion of platinum particles deposit on the outer surface of the carbon support rather than inside the pores, and the inhibition of catalyst poisoning is also unsatisfactory. Medium pore sizes of approximately 2 to 10 nm have been shown to effectively balance ionomer poisoning suppression and proton transport, and exhibit oxygen transport performance far superior to commercial toners and porous carbon supports in the high current density region.

[0018] A third aspect of this invention discloses a method for preparing a layered mesoporous carbon platinum-based catalyst, comprising the following steps: S4. Platinum precursor loading: The mesoporous carbon support described above is dispersed in a platinum salt precursor solution, and adsorption or permeation loading is performed to allow Pt ions to uniformly enter the mesoporous structure and the interior of the mesoporous channels (Pt can be controlled by adjusting the solution pH or ionic strength). 2+ / Pt 4+ (adsorption efficiency), followed by drying; S5. Reduction generation of platinum nanoparticles: The material loaded with platinum precursor obtained in step S4 is thermally reduced in a reducing atmosphere, or the platinum precursor is chemically reduced in liquid phase to reduce the platinum precursor into nano-sized platinum particles, which are uniformly anchored on the surface and pores of the lamellar mesoporous carbon. S6. Washing and drying: The product after reduction in S5 is washed and dried to remove residual ions and byproducts to obtain the lamellar mesoporous carbon-platinum-based catalyst.

[0019] More preferably, in step S4, the platinum salt precursor is chloroplatinic acid, platinum tetrachloride, potassium chloroplatinate, platinum nitrate, or platinum acetylacetonate, the platinum mass concentration is 0.1 mg / mL-10 mg / mL, the static adsorption time is 6-12 hours, and the product is transferred to an oven at 60-80 ℃ for drying for 6-12 hours.

[0020] More preferably, in step S5, the reducing atmosphere is hydrogen, a hydrogen-argon mixture, methane, or carbon monoxide, the thermal reduction temperature is 200-600 °C, and the heating rate is 1-5 °C / min. -1 The heat preservation time is 1-10 hours.

[0021] More preferably, in step S6, the catalyst solid is separated by high-speed centrifugation or vacuum filtration, washed 3-5 times with deionized water, and then dried in a vacuum oven at 60-80°C for 12-24 hours.

[0022] A fourth aspect of this invention discloses a layered mesoporous carbon-platinum-based catalyst prepared by the above method, the catalyst comprising: Layered mesoporous carbon supports, and Highly dispersed platinum nanoparticles uniformly anchored on the surface of the layered mesoporous carbon carrier and within the mesoporous channels; The layered mesoporous carbon support has a two-dimensional open morphology and a mesoporous network with uniform pore size.

[0023] More preferably, the particle size of the platinum nanoparticles is 2 nm to 4 nm; Further preferred, after 30,000 cycles at 0.6-1.0V (vs. RHE) potential, the mass-to-activity decay rate of the lamellar mesoporous carbon support is less than 10%; Further optimized, after 30,000 cycles at a potential of 0.6-1.0V (vs. RHE), the particle size increase is less than 30%. The fifth aspect of this invention discloses the application of the above-mentioned lamellar mesoporous carbon platinum-based catalyst in the oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell.

[0024] The sixth aspect of this invention discloses the application of the above-mentioned mesoporous carbon platinum-based catalyst in an electrochemical energy conversion device.

[0025] Compared with the prior art, the beneficial effects of this invention are as follows: (1) The layered structure is controllable and the mesoporous system is uniform, which significantly improves the mass transfer capacity of the carrier. The layered mesoporous carbon carrier constructed by the present invention through layer self-assembly and stepwise carbonization technology has a two-dimensional open structure and uniform pore size mesoporous channels, which can effectively shorten the electron transport path and improve the oxygen diffusion efficiency. It overcomes the problems of severe pore accumulation and limited internal mass transfer in traditional carbon black carriers, thereby significantly improving the kinetic process of oxygen reduction reaction.

[0026] (2) The platinum nanoparticles are uniformly loaded and highly dispersed, resulting in a significantly improved metal utilization rate. The confined space, nitrogen-containing functional groups, and surface polar sites within the lamellar mesoporous carbon can stably adsorb and coordinate with the platinum precursor, allowing platinum ions to be uniformly anchored on the carbon support. Through controlled reduction, platinum nanoparticles with a stable particle size of 2-3 nm are formed. Compared to the poor dispersion and uneven aggregation of platinum particles in conventional Pt / C catalysts, this invention significantly improves the effective utilization rate of platinum.

[0027] (3) Enhanced metal-support interaction significantly improves the stability of platinum particles. During carbonization, the lamellar mesoporous carbon forms a highly graphitized region and introduces a certain proportion of nitrogen functional groups. These structural features can enhance the interfacial coupling between platinum and the support, inhibit the migration, aggregation and dissolution of platinum particles during electrochemical cycling, thereby significantly improving the durability and cycle life of the catalyst.

[0028] (4) Strong electrochemical corrosion resistance, effectively improving structural stability and long-term performance. The mesoporous carbon structure constructed in this invention has high antioxidant stability and can effectively resist corrosion of the carbon support by high potential and acidic environment; at the same time, its layered structure can buffer the volume changes caused by repeated electrochemical impacts and avoid structural collapse. Compared with traditional carbon black supports, this invention has better structural stability and electrode environment adaptability.

[0029] (5) Excellent overall oxygen reduction catalytic performance, especially in the high current density region. Due to the rapid electron transport and effective gas diffusion channels brought about by the layered mesoporous structure, coupled with the high activity of the highly dispersed platinum particles, the catalyst of this invention exhibits a higher half-wave potential, a larger specific activity, and a lower potential decay in the ORR test. It maintains a high limiting current density in the high current density region, which is significantly better than that of traditional Pt / C catalysts.

[0030] (6) The preparation process is simple and reproducible, making it suitable for large-scale production. The self-assembly-carbonization-loading-reduction strategy adopted in this invention has clear steps, mild conditions, and controllable processes, and does not rely on hazardous chemicals or difficult processing. Its structure is highly controllable and has good batch reproducibility, possessing the potential for large-scale preparation and suitable for scientific research and industrial production applications. Attached Figure Description

[0031] Figure 1 These are nitrogen isothermal adsorption-desorption curves of the sheet-like mesoporous carbon support synthesized in Example 1 of this invention, wherein (a) is a sheet-like mesoporous carbon support with an average pore diameter of 2 nm, denoted as LMC-2, (b) is a sheet-like mesoporous carbon support with an average pore diameter of 5 nm, denoted as LMC-5, and (c) is a sheet-like mesoporous carbon support with an average pore diameter of 10 nm, denoted as LMC-10.

[0032] Figure 2 These are transmission electron microscope (TEM) images of LMC-5, a sheet-like mesoporous carbon support with an average pore diameter of 5 nm, in Embodiment 1 of the present invention. In (a), the icon bar is 50 nm, showing the two-dimensional sheet-like overall morphology of the material; and in (b), the icon bar is 10 nm, showing the mesoporous structure with a relatively uniform pore size distribution at high magnification.

[0033] Figure 3 The figures are chronocurrent curves obtained at 1.2V after 600 seconds of electrochemical oxidation in nitrogen-saturated 0.1 M HClO4 using the sheet-like mesoporous carbon support LMC-5 synthesized in Example 1 of this invention and the commercial carbon support ECP600.

[0034] Figure 4 (a) is the ORR polarization curve of the lamellar mesoporous carbon platinum-based catalyst Pt / LMC-5 sample in Example 1 of the present invention at a low initial potential of 0.6-1.0V and after 30,000 cycles; Figure 4 (b) is the ORR polarization curve of the commercial platinum-carbon catalyst TKK60 sample in the comparative example of the present invention at a low initial potential of 0.6-1.0V and after 30,000 cycles.

[0035] Figure 5(a) is the X-ray powder diffraction pattern of the lamellar mesoporous carbon platinum-based catalyst Pt / LMC-5 sample in Example 1 of the present invention before and after 30,000 cycles at a low potential of 0.6-1.0V; Figure 5 (b) is the X-ray powder diffraction pattern of the commercial platinum-carbon catalyst TKK60 sample in the comparative example of the present invention before and after 30,000 cycles at a low potential of 0.6-1.0V. Detailed Implementation

[0036] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Process parameters not specified in the embodiments of this application can be carried out according to conventional methods, and the raw materials used can be obtained through commercial channels.

[0037] This invention provides a method for preparing a tunable and highly stable sheet-like mesoporous carbon-platinum-based catalyst, comprising the following steps: (1) Precursor solution construction and directional self-assembly: 1.0 g of dopamine hydrochloride was weighed as a carbon source and slowly added to a mixed solution of methanol and deionized water, wherein the volume ratio of methanol to water in the mixed solution was 3:1. After magnetic stirring until completely dissolved, 1.0 g of structure-directing agent Pluronic F127 was added to form stable micelles in the alcohol-water system. 0.5 mL of ammonia (25-28 wt%) and 0.5 g of urea were then added as layer control agents to regulate pH and hydrogen bond structure in the system, inducing the precursor to grow along a two-dimensional direction. Subsequently, the solution was magnetically stirred at room temperature for 1 h to obtain a uniform and transparent precursor solution, enabling the system to meet the self-assembly conditions for forming a layered structure.

[0038] (2) Pour the precursor solution obtained in step (1) into a clean glass petri dish, ensuring the solution thickness is controlled at 2-3 mm. Place the petri dish in a constant temperature incubator, setting the temperature to 35 ℃ and the relative humidity to 40%. Under these conditions, solvent evaporation-induced self-assembly is performed for 12 h, allowing the carbon source and template molecules to align in a two-dimensional direction to form a layered organic-inorganic composite gel. After the evaporation process is complete, transfer the sample to a vacuum drying oven and dry it at 60 ℃ for 10 h to obtain a solid precursor.

[0039] (3) After gently grinding the obtained dry gel, spread it evenly in an alumina crucible and place it in the central area of ​​a tube furnace. Purge the air with nitrogen for 20 min to provide an inert atmosphere. Perform stepwise heat treatment according to the following procedure: Pre-carbonization stage: at 2℃·min-1 The heating rate was increased to 450 °C, and the temperature was maintained at this level for 1.5 h to allow the soft template to begin decomposition and volatilization, while simultaneously fixing the lamellar morphology and reducing the structural damage caused by volume shrinkage. High-temperature carbonization stage: The heating rate was continued at 2 °C / min. -1 The heating rate was increased to 850 °C and held for 1 h to enhance the graphitization of the carbon framework, improve conductivity, and form a layered mesoporous carbon support with a uniform mesoporous structure. After carbonization, the sample was naturally cooled to room temperature under nitrogen protection. The resulting sample was washed once with deionized water and dried at 60 °C for 6 h to obtain the support LMC-5.

[0040] (4) 200 mg of lamellar mesoporous carbon LMC-5 was added to 0.2 mL of deionized water and ultrasonically soaked for 10 min. Then, 0.6 mL of chloroplatinic acid aqueous solution was added to make the mass fraction of platinum metal in the catalyst 60%. After standing adsorption at room temperature for 10 h, the sample was collected by centrifugation and transferred to an oven. It was dried at 60 ℃ for 10 h to obtain platinum precursor-supported lamellar mesoporous carbon powder.

[0041] (5) Spread the powder obtained in step (4) evenly in an alumina crucible and place it in a tube furnace. Infuse the furnace with argon gas (50 mL / min). -1 At 2 °C·min under an atmosphere -1 The temperature was raised to 200 °C, then switched to a reducing atmosphere of 5% H₂ / Ar. The temperature was then increased to 300 °C at the same rate and held for 2 h to reduce the adsorbed platinum precursor into nanoscale platinum particles, which were then uniformly anchored on the surface and within the pores of the mesoporous carbon. After reduction, the sample was cooled to room temperature under argon protection and removed.

[0042] (6) The sample obtained in step (5) was separated by high-speed centrifugation (8000 rpm) and washed four times with deionized water to remove residual chloride ions and byproducts. After washing, the solid sample was dried in a vacuum oven at 60 ℃ for 18 h to finally obtain the layered mesoporous carbon supported highly dispersed platinum nanoparticle electrocatalyst Pt / LMC-5.

[0043] Example 2: The preparation and reaction were carried out using the method of Example 1, the only difference being that the template in step (1) was replaced with CTAB (1 g), and a hydrophilic solvent system of methanol / water = 1:3 was used to shrink the micelle size. After carbonization, the pore size of the lamellar mesoporous carbon support was reduced to 2-3 nm, yielding LMC-2.

[0044] Example 3: The preparation and reaction were carried out using the method of Example 1, except that the template in step (1) was replaced with P123.

[0045] Example 4: The preparation and reaction were carried out using the method of Example 1, except that the layer regulator in step (1) was replaced with triethanolamine.

[0046] Example 5: The preparation and reaction were carried out using the method of Example 1, with the only difference being that the alcohol-water system in step (1) was adjusted to: ethanol / water = 5:1 (v / v), and TMB (TMB / F127 = 0.5) was added to the precursor solution as a swelling agent to induce a larger micelle core size. After carbonization, the pore size of the resulting lamellar mesoporous carbon increased from about 5 nm to about 10 nm, yielding LMC-10.

[0047] Example 6: The preparation and reaction were carried out using the method of Example 1, keeping the precursor unchanged. The only difference was that the pre-carbonization temperature in step (3) was reduced from 450 °C to 400 °C and kept at that temperature for 2 h.

[0048] Example 7: The preparation and reaction were carried out using the method of Example 1, keeping the precursor unchanged. The only difference was that the high-temperature carbonization temperature in step (3) was increased from 450 °C to 500 °C and kept at that temperature for 2 h.

[0049] Example 8: The preparation and reaction were carried out using the method of Example 1, keeping the precursor unchanged. The only difference was that the high-temperature carbonization temperature in step (3) was reduced from 850 °C to 800 °C and kept at that temperature for 2 h.

[0050] Example 9: The preparation and reaction were carried out using the method of Example 1, keeping the precursor unchanged. The only difference was that the high-temperature carbonization temperature in step (3) was increased from 850 °C to 900 °C and kept at that temperature for 2 h. The pore size was reduced by the shrinkage of the carbon skeleton, and the degree of graphitization was increased at the same time.

[0051] Example 10: The preparation and reaction were carried out using the method of Example 1, keeping the precursor unchanged. The only difference was that the pre-carbonization stage in step (3) was omitted, and the carbonization was carried out directly at a high temperature of 850 °C for 2 h. The test showed that the BET specific surface area decreased significantly (from 1385 to 400 m2 / g), and a broad disordered peak appeared in the pore size distribution diagram. The results indicate that distributed carbonization is more important for the formation of mesoporous carbon with a suitable specific surface area and pore size.

[0052] Example 11: The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (1), the structure directing agent was changed from F127 to P123 (2 g), and an isopropanol / water mixed solvent of 3:1 was used to form a larger-scale template arrangement. The resulting mesoporous carbon had an increased pore size and a significantly increased pore volume.

[0053] Example 12: The preparation and reaction were carried out using the method of Example 1, the only difference being that in step (1), the amount of dopamine was increased from 1.0 g to 2.5 g to increase the solid content of the solution, so that multi-layer stacks could be formed during self-assembly.

[0054] Example 13: The preparation and reaction were carried out using the method of Example 1, the only difference being that the evaporation conditions in step (2) were set to 30 °C, 55% relative humidity, and aging for 24 h, to slow down the solvent evaporation rate and promote full stacking between layers.

[0055] The results and data from the above embodiments were analyzed, such as... Figure 1 As shown in Table 1, the BET specific surface area and pore volume and pore size distribution of LMC-2, LMC-5 and LMC-10 can be calculated from the nitrogen adsorption-desorption isotherms in Figures (a), (b) and (c).

[0056] Table 1 Calculation Results like Figure 2 The images shown are transmission electron microscope (TEM) images of the sheet-like mesoporous carbon carrier LMC-5. As can be seen from (a), the prepared mesoporous carbon carrier LMC-5 sample exhibits a sheet-like morphology. (b) further shows that the sample is mesoporous carbon with a pore size of about 5 nm and is uniformly distributed.

[0057] like Figure 3 The figure shows the chronoamperometry curve of the carbon support after 600 seconds of electrochemical oxidation in nitrogen-saturated 0.1 M HClO4 at 1.2 V, illustrating the corrosion resistance of the carbon material. The lower the limiting current density of the carbon material, the better its corrosion resistance. In Example 1, the lamellar mesoporous carbon support LMC-5 exhibits a significantly lower corrosion current than the commercial carbon support ECP600, indicating that LMC-5 has a higher degree of graphitization, is resistant to high-potential oxidation, and possesses excellent corrosion resistance under acidic conditions.

[0058] The oxygen evolution reaction (ORR) activity and durability of the catalyst were studied using electrochemical testing (linear sweep voltammetry, LSV). The mass activity (MA) was used to evaluate the ORR performance of the catalyst samples.

[0059] Linear scanning voltammetry: Electrodes were placed in an electrolytic cell to form a three-electrode system. The working electrode was a glassy carbon electrode coated with the catalyst sample, the reference electrode was Hg / Hg2SO4, and the counter electrode was a platinum mesh electrode. To evaluate the ORR electrocatalytic performance of the catalyst materials and their performance in the reaction process, a rotating disk electrode cathodic polarization test was performed. After saturating the 0.1M HClO4 electrolytic cell with O2, the rotation speed of the glassy carbon working electrode was adjusted to 1600 rpm, and a scan was performed in the range of -0.671 to 0.379 V at a scan rate of 10 mV / s.

[0060] like Figure 4 As shown in (a), the ORR polarization curves of the lamellar mesoporous carbon platinum-based catalyst Pt / LMC-5 sample in Example 1 of this invention were tested at an initial low potential of 0.6-1.0V and after 30,000 cycles. From the half-wave potential, the ORR performance was enhanced after 30,000 cycles compared to the initial state. Figure 4 As shown in (b), the ORR polarization curves of the commercial platinum-carbon catalyst TKK60 sample in the comparative example of this invention were tested at a low initial potential of 0.6-1.0V and after 30,000 cycles. From the half-wave potential, the ORR performance was significantly weakened after 30,000 cycles compared to the initial state.

[0061] The kinetic current density was calculated by measuring the current density and the limiting current density, and the mass ratio activity MA was calculated based on the kinetic current density and the actual mass of platinum, as shown in Table 2.

[0062] Table 2 Calculation Results As shown in Table 2, the Pt / LMC-5 sample of the mesoporous carbon platinum-based catalyst in Example 1 showed a 5.1% increase in specific activity after 30,000 accelerated cycling cycles. In contrast, the TKK60 sample of the commercial platinum-carbon catalyst in the comparative example showed an 11.0% decrease in specific activity after 30,000 accelerated cycling cycles. Compared to the commercial platinum-carbon catalyst, the initial performance and stability of the Pt / LMC-5 mesoporous carbon platinum-based catalyst were significantly improved.

[0063] according to Figure 5 The X-ray powder diffraction patterns shown in Table 3 allow us to calculate the particle size of platinum nanoparticles in the lamellar mesoporous carbon platinum-based catalyst Pt / LMC-5 and the commercial platinum-carbon catalyst TKK60 before and after 30,000 cycles at low potentials of 0.6–1.0 V using the Scherrer formula.

[0064] Table 3 Calculation Results As shown in Table 3, the Pt / LMC-5 sheet-like mesoporous carbon platinum-based catalyst sample in Example 1 exhibited a 20.7% increase in platinum nanoparticle size after 30,000 accelerated cycling cycles. In contrast, the commercial platinum-carbon catalyst TKK60 sample in the comparative example showed an 88.0% increase in platinum nanoparticle size after the same test. Therefore, the Pt / LMC-5 sheet-like mesoporous carbon platinum-based catalyst demonstrates better platinum particle stability compared to the commercial platinum-carbon catalyst. Figure 3 The results are consistent with those in Table 2. The core reason lies in the fact that the two-dimensional lamellar structure and the well-organized mesoporous network of the Pt / LMC-5 catalyst jointly achieve higher platinum exposure, better electron transport, faster gas and ion diffusion, and stronger structural stability. The lamellar structure provides flat and open active sites and significantly improves platinum utilization; the mesoporous channels reduce mass transfer resistance and suppress concentration polarization; the highly graphitized carbon framework ensures excellent conductivity and corrosion resistance; and the synergistic confinement effect of lamellar and mesoporous structures makes platinum nanoparticles more anchored, less prone to migration, sintering, or dissolution. Therefore, this catalyst simultaneously achieves higher initial ORR activity, a larger limiting current density, and significantly enhanced durability, with overall performance far superior to the traditional commercial platinum-carbon catalyst TKK60.

[0065] This invention is not limited to the above-described embodiments. Any changes in shape or structure are within the scope of protection of this invention. The scope of protection of this invention is defined by the appended claims. Those skilled in the art can make various changes, modifications, substitutions, combinations, and simplifications to these embodiments without departing from the principles and essence of this invention. All such changes and simplifications should be considered equivalent substitutions and fall within the scope of protection of this invention.

Claims

1. A method for preparing a layered mesoporous carbon support, characterized in that, Includes the following steps: S1. Precursor solution construction and directional self-assembly: A carbon source, a structure directing agent, and a layering regulator are dissolved in a mixed solution of alcohol and water to form a homogeneous and transparent precursor solution; wherein the carbon source is a nitrogen-containing carbon source, and the layering regulator is selected from one or more of urea, ammonia, or triethanolamine. S2. Formation of sheet gel: The precursor solution obtained in step S1 is subjected to solvent evaporation to induce self-assembly or sol-gel reaction, so that the carbon source and template molecules are oriented in two dimensions to form a sheet-like organic-inorganic composite gel, which is then dried to obtain a solid precursor; S3. Stepwise carbonization and template removal of mesoporous carbon support: The solid precursor obtained in step S2 is subjected to stepwise heat treatment under an inert atmosphere: First, pre-carbonization is carried out at 400-500 ℃ to allow the template to decompose and volatilize, while fixing the lamellar morphology and reducing damage caused by volume shrinkage; then, high-temperature carbonization is carried out at 800-900 ℃ to enhance the graphitization degree of the carbon skeleton, improve conductivity, and achieve in-situ doping of nitrogen, ultimately forming a lamellar mesoporous carbon support with a two-dimensional lamellar morphology, uniform pore size, and nitrogen-doped functional groups on the surface.

2. The method for preparing a sheet-like mesoporous carbon support according to claim 1, characterized in that, In step S1, the structure directing agent is block copolymer F127; the layer control agent is urea and / or ammonia; the carbon source is dopamine; the nitrogen-containing carbon source and the nitrogen-containing layer control agent work synergistically during self-assembly and carbonization to achieve uniform, stable and controllable nitrogen doping; the alcohol is one or a mixture of methanol, ethanol, isopropanol or ethylene glycol.

3. The method for preparing a sheet-like mesoporous carbon support according to claim 1, characterized in that, In step S3, the pre-carbonization heating rate is 1-5 °C·min. -1 The holding time is 1-3 hours; the high-temperature carbonization heating rate is 1-5℃·min. -1 The heat preservation time is 1-3 hours.

4. The method for preparing a sheet-like mesoporous carbon support according to claim 1, characterized in that, In step S2, the solvent evaporation-induced self-assembly or sol-gel reaction is carried out under constant temperature conditions; the temperature of the constant temperature conditions is 30-40 ℃, the relative humidity is 30-60%, and the holding time is 6-24 hours.

5. A layered mesoporous carbon support, characterized in that, Prepared by the method of any one of claims 1-4, the layered mesoporous carbon support has a two-dimensional open-morphology mesoporous network, and its surface contains nitrogen-doped functional groups; the average pore size of the layered mesoporous carbon support is 2-10 nm, and the BET specific surface area is 500-2000 m². 2 / g.

6. A method for preparing a layered mesoporous carbon platinum-based catalyst, characterized in that, Includes the following steps: S4. Platinum precursor loading: The sheet-like mesoporous carbon support as described in claim 5 is dispersed in a platinum salt precursor solution, and adsorption or permeation loading is performed to allow Pt ions to uniformly enter the sheet structure and mesoporous channels, followed by drying. S5. Reduction generation of platinum nanoparticles: The material loaded with platinum precursor obtained in step S4 is thermally reduced in a reducing atmosphere, or the platinum precursor is chemically reduced in the liquid phase. S6. Washing and drying: The product after reduction in S5 is washed and dried to obtain the lamellar mesoporous carbon platinum-based catalyst.

7. The method for preparing a layered mesoporous carbon-platinum-based catalyst according to claim 6, characterized in that, In step S5, the reducing atmosphere is hydrogen, a hydrogen-argon mixture, methane, or carbon monoxide; the thermal reduction temperature is 200-600 °C; and the heating rate is 1-5 °C / min. -1 The heat preservation time is 1-10 hours.

8. The method for preparing a layered mesoporous carbon-platinum-based catalyst according to claim 6, characterized in that, In step S4, the platinum salt precursor is chloroplatinic acid, platinum tetrachloride, potassium chloroplatinate, platinum nitrate, or platinum acetylacetonate, with a platinum mass concentration of 0.1-10 mg / mL, a static adsorption time of 6-12 hours, and then transferred to an oven at 60-80 ℃ for drying for 6-12 hours.

9. A layered mesoporous carbon-platinum based catalyst, characterized in that, include: The sheet-like mesoporous carbon support as described in claim 5; as well as Platinum nanoparticles are uniformly anchored on the surface of the carrier and within the mesoporous channels; the particle size of the platinum nanoparticles is 2-4 nm.

10. The application of the lamellar mesoporous carbon platinum-based catalyst as described in claim 9 in the oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell.

Images