Preparation method of ordered mesoporous nanosheet loaded superfine Pt-based alloy catalyst

Abstract

The invention relates to the technical field of Pt-based alloy catalysts and preparation thereof, and discloses a preparation method of an ordered mesoporous nanosheet loaded superfine Pt-based alloy catalyst, which comprises the following steps: by taking F127 as a mesoporous template agent, Resol as a carbon source and NaCl as a hard template, carrying out solution mixing, negative pressure suction filtration forming, step-by-step curing, inert atmosphere calcination and other processes to prepare the ordered mesoporous nanosheet loaded superfine Pt-based alloy catalyst. The ordered mesoporous nanosheet loaded superfine Pt-based alloy catalyst is successfully prepared, a plurality of similar problems in the prior art are effectively solved, and the preparation method has an important industrial value for preparing a high-performance Pt-based alloy catalyst.

Description

Technical Field

[0001] This invention relates to the field of Pt-based alloy catalysts and their preparation technology, specifically to a method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst. Background Technology

[0002] Pt-based catalysts are indispensable in fuel cells, catalytic hydrogenation, and VOCs oxidation due to their excellent catalytic activity. However, the scarcity and high cost of Pt limit its large-scale application. Alloying Pt with transition metals such as Ir, Pd, and Rh can reduce the amount of Pt required and improve catalytic performance through electronic / geometric effects. However, there are still some drawbacks in actual preparation: the size of ultrafine (1~3 nm) alloy particles is difficult to control precisely and they are not evenly dispersed; the interaction between the support and the particles is weak, and active sites are easily lost; high-temperature treatment can easily cause particle agglomeration and support pore collapse, affecting performance and lifespan.

[0003] To address the aforementioned shortcomings, existing technologies improve preparation efficiency and structural stability through both carrier optimization and process improvement. Regarding carriers, ordered mesoporous carbon and mesoporous oxides are preferred, utilizing their high specific surface area and ordered pores to enhance the loading of active sites and mass transfer efficiency. In terms of processes, synthesis strategies such as co-reduction and impregnation methods are developed, and reaction parameters are controlled to achieve the synthesis of ultrafine particles. Simultaneously, the interaction between the carrier and particles is strengthened and aggregation is suppressed by introducing surfactants, doping with heteroatoms, or optimizing high-temperature post-treatment parameters.

[0004] However, the existing technology still has the following technical problems: (1) It is difficult to control the structure of the ordered mesoporous carrier, and it has poor compatibility with ultrafine Pt-based alloy particles, making it difficult to achieve uniform and stable immobilization; (2) The existing preparation process is complicated, has poor controllability, and poor structural reproducibility, which is not conducive to large-scale production; (3) The problems of particle agglomeration and pore collapse under high temperature treatment have not been fundamentally solved, affecting long-term stability; (4) Some process aids remain and can easily block active sites, reducing catalytic efficiency. Therefore, it is urgent to develop a new technical solution that takes into account ultrafine particle control, high dispersibility, structural stability and large-scale preparation. Summary of the Invention

[0005] The present invention aims to provide a method for preparing an ultrafine Pt-based alloy catalyst supported on ordered mesoporous nanosheets, in order to solve the technical problems of existing ordered mesoporous supports being difficult to control in terms of structure, having poor compatibility with ultrafine Pt-based alloy particles, and being difficult to achieve uniform and stable immobilization.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst, comprising the following steps: Step 1, Preparation of Solution A: Dissolve F127 in THF solution, disperse by ultrasonication, add Resol / THF solution, and stir for 10 min to form a homogeneous solution A; Step 2, Preparation of solution B: Dissolve Pt(acac)2 and Ir(acac)3 together in ethanol and stir for 10 min to form a yellow transparent solution B; Step 3: Preparation of precursor mixed solution: Mix solution A and solution B, and stir at room temperature for 30 minutes to make them evenly mixed and form a homogeneous precursor solution; Step 4, Template Immersion and Shaping: Pour the thoroughly mixed precursor solution into a beaker containing NaCl solid and immerse it to allow the solution to fully penetrate the gaps between the NaCl solid. Filter under negative pressure to obtain a light yellow solid shaped by the NaCl template. Step 5: Curing treatment: After drying the light yellow solid at low temperature, heat the mixture to cure and set its shape; Step 6, Inert atmosphere calcination: The solidified solid sample is transferred to a tube furnace for calcination to obtain a gray solid; Step 7: Template removal and drying: Rinse the calcined gray solid repeatedly with deionized water to remove NaCl, and then vacuum dry to obtain the ordered mesoporous nanosheet supported ultrafine Pt-based alloy catalyst product.

[0007] The principles and advantages of this scheme are: This invention proposes a novel method with a simple process flow, mild conditions, and precise control over alloy particle size and mesoporous structure. Using F127 as a mesoporous template agent, Resol as a carbon source, and NaCl as a hard template, an ultrafine Pt-based alloy catalyst supported on ordered mesoporous nanosheets was successfully prepared through processes such as solution mixing, negative pressure filtration molding, stepwise solidification, and inert atmosphere calcination. This method effectively solves many similar problems existing in the prior art and has crucial industrial value for the preparation of high-performance Pt-based alloy catalysts.

[0008] Preferably, as an improvement, in step one, the mass-to-volume ratio of F127, THF solution, and Resol / THF solution is 0.1~0.5g:5~10ml:2~4.3g, and the mass fraction of Resol / THF solution is 20~35%; the ultrasonic dispersion time is 15~30min, and the power is 80~120W.

[0009] Beneficial Effects: This solution, employing the aforementioned method, facilitates the molecular-level uniform dispersion of the template agent and resin precursor, precisely constructing a mesoporous-guided precursor system. This lays a solid foundation for subsequent ordered mesoporous structure formation and uniform loading of ultrafine Pt-based alloy particles. Through long-term experiments, the inventors discovered that if the proportion of F127 is too low, a complete mesoporous-guided micelle structure cannot be formed, resulting in disordered mesoporous channels, large pore size deviations, and a significant decrease in the specific surface area of ​​the carrier, making it difficult to load a sufficient amount of ultrafine alloy particles. Conversely, if the proportion of F127 is too high, it leads to increased template agent residue, causing mesoporous channels to collapse easily after calcination and diluting the resin concentration, affecting the structural strength of the carrier after carbonization. Furthermore, if the amount of THF solution is too low, the system viscosity is high, leading to uneven dispersion and agglomeration of F127 and Resol resin; if the amount of THF solution is too high, it reduces the precursor concentration, resulting in a loose mesoporous structure after molding and poor mechanical stability of the carrier. If the Resol / THF solution mass fraction is too low, insufficient resin content will prevent the formation of a continuous mesoporous carbon framework. If the THF solution mass fraction is too high, the solution viscosity will increase sharply, leading to poor compatibility with F127 and easy phase separation, resulting in local deficiencies in the mesoporous structure. If the Resol / THF solution ratio is too low, the resin precursor volume will be insufficient, resulting in excessively high porosity and weak load-bearing capacity after the mesoporous support is formed. If the Resol / THF solution ratio is too high, it will encapsulate the template agent, hindering the subsequent orderly formation of mesoporous channels. If the ultrasonic dispersion time is too short or the power is too low, the F127 agglomerates cannot be broken, resulting in uneven dispersion of the template agent and resin and poor mesoporous guiding effect. If the ultrasonic time is too long or the power is too high, the strong shear force of the ultrasound will destroy the micelle pre-assembled structure and cause rapid solvent evaporation, leading to an imbalance in the distribution of system components. Ultimately, this results in disordered mesoporous structure of the catalyst, uneven loading of alloy particles, and a significant reduction in catalytic activity and structural stability.

[0010] Preferably, as an improvement, in step two, the mass-to-volume ratio of Pt(acac)2, Ir(acac)3 and ethanol is 9~37mg:7~15mg:10~25mL.

[0011] Beneficial Effects: This scheme, employing the aforementioned method, facilitates the complete dissolution and uniform molecular-level dispersion of the two metal precursors, forming a stable, transparent yellow solution. This ensures precise particle ratios and uniform, ultra-fine Pt-Ir alloy particles, providing a uniform metal source for highly active catalysts. Through long-term experiments, the inventors discovered that insufficient Pt(acac)2 leads to insufficient active components and decreased catalytic activity; excessive Pt(acac)2 can cause particle agglomeration, hindering the formation of ultra-fine alloys and increasing costs. Insufficient Ir(acac)3 makes it difficult to improve performance through alloying effects; excessive Ir(acac)3 disrupts the optimal ratio, inhibits Pt active sites, and induces lattice distortion, reducing stability. Insufficient ethanol concentration results in incomplete dissolution and precipitation of the precursors, leading to disordered alloy particle distribution; excessive ethanol concentration dilutes the concentration, resulting in insufficient active site density, increased energy consumption, and precursor loss, ultimately leading to low catalytic efficiency and poor performance consistency.

[0012] Preferably, as an improvement, in step four, the NaCl crystals have a particle size of 50~200μm and are used in an amount of 1.5~3 times the volume of the precursor mixed solution.

[0013] Beneficial Effects: This scheme, employing the aforementioned method, facilitates uniform infiltration and shaping of the precursor through its gaps, ensuring the orderliness of the mesoporous structure and providing a structural basis for the uniform loading of ultrafine Pt-based alloy particles. Through long-term experiments, the inventors discovered that if the NaCl particle size is too small, the gaps are narrow, hindering precursor infiltration and resulting in uneven distribution and disordered mesoporous structure; if the NaCl particle size is too large, the gaps are too large, leading to a loose carrier structure, disordered pores, and reduced load-bearing capacity after shaping. If the NaCl dosage is too low, a complete shaped framework cannot be formed, causing the precursor to easily flow and collapse; if the NaCl dosage is too high, it coats the precursor, making it difficult to remove completely later, and residual NaCl will clog pores, cover active sites, and reduce catalytic efficiency.

[0014] Preferably, as an improvement, in step four, the pressure of the negative pressure filtration is lower than 0.03 MPa.

[0015] Beneficial Effects: This scheme, employing the aforementioned method, facilitates the rapid removal of excess solvent from the system, achieving dense and uniform shaping of the precursor within the NaCl interstices. This ensures the regularity and shaping effect of the mesoporous structure, laying a solid foundation for the subsequent stability of the catalyst structure. Through long-term experiments, the inventors discovered that if the pressure is too low, insufficient filtration power and slow solvent removal can easily cause precursor flow deviation, resulting in uneven solid formation, disordered mesoporous channel arrangement, and excessive residual solvent in the system, increasing subsequent drying energy consumption. Conversely, if the pressure is too high, the filtration rate is too fast, easily causing the precursor to rapidly escape with the solvent, resulting in the loss of both the metal active component and the carrier precursor. Simultaneously, strong negative pressure can cause pores and cracks in the precursor layer within the NaCl interstices, leading to a loose structure after shaping. Subsequent calcination can easily cause channel collapse, ultimately resulting in insufficient catalyst loading and a significant decrease in activity and stability.

[0016] Preferably, as an improvement, in step five, the low-temperature drying is slow drying in an oven at 40~60℃ for 12~24h to completely evaporate solvents such as THF; the temperature curing is heating to 100~130℃ and maintaining it for 2~4h for curing and shaping.

[0017] Beneficial Effects: This solution employs the above-mentioned method, facilitating gentle solvent removal and achieving stable carrier shaping, avoiding structural collapse and precursor agglomeration, and ensuring the regularity of the mesoporous framework and the uniformity of the metal composition. Through long-term experiments, the inventors discovered that if the drying temperature is too low or the time is insufficient, the solvent will not evaporate completely, and residual solvent can easily cause pore cracking during subsequent curing. Conversely, if the temperature is too high or the time is too long, rapid solvent evaporation will impact the precursor system, causing mesoporous structure disorder and localized agglomeration of the metal precursor. If the curing temperature is too low or the time is insufficient, the resin cross-linking will be incomplete, resulting in poor carrier structural strength and easy collapse during subsequent calcination. Conversely, if the temperature is too high or the time is too long, premature precursor carbonization will occur, destroying the mesoporous guiding structure and causing metal precursor agglomeration, preventing the formation of ultrafine alloy particles.

[0018] Preferably, as an improvement, in step six, the calcination is carried out in an N2 atmosphere with a heating rate of 1~5℃ / min, first heating to 350~450℃ for preheating and stabilizing for 3~5 hours, and then heating to 700~900℃ for high-temperature forging for 2~5 hours.

[0019] Beneficial Effects: This scheme, employing the aforementioned method, facilitates the carbonization and in-situ reduction of Pt-Ir alloy particles, enabling precise reorganization of the internal structure and ensuring a regular mesoporous structure, ultra-fine alloy particles, and uniform dispersion. Through long-term experiments, the inventors discovered that excessively rapid heating rates can lead to excessive local thermal stress, causing mesoporous channel collapse and alloy particle agglomeration. Conversely, excessively slow heating rates prolong the process cycle and increase energy consumption. If the preheating temperature is too low or the preheating time is insufficient, the template agent and organic components will not decompose sufficiently, leaving residual impurities that clog the pores. Excessively high preheating temperatures will prematurely induce particle agglomeration. If the calcination temperature is too low, the resin carbonization will be incomplete, and the alloy particle reduction will be insufficient, resulting in a significant decrease in catalytic activity. Conversely, excessively high calcination temperatures will cause alloy particles to sinter and grow, the mesoporous framework to collapse, and the alloy crystal structure to be damaged, reducing catalyst stability and lifespan.

[0020] Preferably, as an improvement, in step seven, the vacuum drying temperature is 60~80℃ and the time is 6~12h.

[0021] Beneficial Effects: This method, employing the aforementioned approach, facilitates gentle and efficient removal of moisture from samples, ensuring the integrity of the mesoporous channel structure and the stable dispersion of ultrafine Pt-based alloy particles, while avoiding channel collapse and particle agglomeration. Through long-term experiments, the inventors discovered that if the drying temperature is too low or the drying time is insufficient, moisture removal will be incomplete, and residual moisture can easily lead to shrinkage and deformation of the mesoporous channels, reducing the catalyst's structural stability. Conversely, if the drying temperature is too high or the drying time is too long, thermal shrinkage of the mesoporous framework will cause channel collapse, while simultaneously promoting the migration and agglomeration of ultrafine Pt-based alloy particles, reducing the specific surface area of ​​active sites, and significantly decreasing the catalyst's catalytic activity and lifespan.

[0022] Preferably, as an improvement, this solution also provides an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst, prepared by the above method, wherein the Pt-based alloy particles in the catalyst have a particle size of 1-3 nm, a mesopore size of 2-5 nm, and a specific surface area of ​​500-800 m². 2 / g.

[0023] Beneficial effects: The above-mentioned scheme is adopted to maximize the effectiveness of active sites and the advantages of mesoporous mass transfer, and to achieve the optimal match between catalytic activity, selectivity and structural stability, which is the core indicator to ensure high-performance Pt-based alloy catalysts.

[0024] Preferably, as an improvement, this solution also provides an application of an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst, which is used in fuel cells, catalytic hydrogenation reactions, or VOCs catalytic oxidation reactions. Attached Figure Description

[0025] Figure 1The XRD diffraction pattern of the ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst prepared in Example 1 of this invention (comparison of catalysts with different Pt / Ir ratios).

[0026] Figure 2 The image shows a TEM image (200 nm) of the catalyst prepared in Example 1 of this invention.

[0027] Figure 3 The image shows an STM image (100 nm) of the catalyst prepared in Example 1 of this invention.

[0028] Figure 4 This is an elemental mapping analysis diagram of the catalyst prepared in Example 1 of the present invention.

[0029] Figure 5 This is a high-resolution TEM image (100 nm) of the catalyst prepared in Example 1 of the present invention.

[0030] Figure 6 The images show the TEM image and particle size distribution of the catalyst prepared in Comparative Example 1 of this invention.

[0031] Figure 7 The image shows the TEM image and particle size distribution of the catalyst prepared in Comparative Example 2 of this invention.

[0032] Figure 8 The image shows the TEM image and pore size distribution of the catalyst prepared in Comparative Example 3 of this invention.

[0033] Figure 9 The image shows the TEM image and particle size distribution of the catalyst prepared in Comparative Example 4 of this invention.

[0034] Figure 10 This is an elemental mapping analysis diagram of the catalyst prepared in Comparative Example 4 of this invention.

[0035] Figure 11 The image shows the TEM image and particle size distribution of the catalyst prepared in Comparative Example 5 of this invention.

[0036] Figure 12 This is an elemental mapping analysis diagram of the catalyst prepared in Comparative Example 5 of this invention.

[0037] Figure 13 This is a comparison diagram of the catalytic activity of the catalysts obtained in Example 1 and Comparative Examples 2-5 of the present invention in the anode reaction of an ethanol fuel cell.

[0038] Figure 14 This is a comparison chart showing the time-dependent decay of catalytic performance between the catalysts prepared in Example 1 and Comparative Example 4 of this invention and conventional catalysts. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials and reagents used can all be obtained commercially. In all experiments, the experimental water was ultrapure water (resistivity ≥18.2 MΩ·cm).

[0040] Example 1 This embodiment details the preparation process, structural characterization, and electrocatalytic performance of an ordered mesoporous nanosheet-supported ultrafine Pt-Ir alloy catalyst in the methanol oxidation reaction, including the following steps: Step 1, Preparation of Solution A: Accurately weigh 0.1 g of triblock copolymer F127 as a mesoporous structure directing agent, dissolve it in 5 mL of tetrahydrofuran (THF), and sonicate at 80 W for 30 min (or sonicate at 80-120 W for 15-30 min) to promote its complete dissolution and dispersion, forming a homogeneous micelle solution. Then add 2.0 g of a 20 wt% methyl phenolic resin (Resol) THF solution as a carbon precursor, and stir at room temperature for 10 min to allow F127 and Resol to achieve preliminary self-assembly at the molecular level, forming a homogeneous and stable solution A. This step lays the molecular template foundation for the subsequent formation of an ordered mesoporous structure.

[0041] Step 2, Preparation of Solution B: Accurately weigh 9 mg of Pt(acac)2 (i.e., di(acetylacetone)platinum(II)) and 7 mg of Ir(acac)3 (i.e., tri(acetylacetone)iridium(III)) as the source of the metal active components, and dissolve them together in 10 mL of ethanol. Stir at room temperature for 10 min until completely dissolved to form a yellow, clear, and transparent solution B. The choice of ethanol as the solvent facilitates uniform mixing with solution A in the subsequent steps.

[0042] Step 3: Preparation of the precursor mixture solution: Under continuous stirring, the "basic slurry" solution A is slowly added to the "active raw material solution" solution B, and the mixture is stirred at room temperature for 30 minutes. This process promotes the synergistic interaction between the metal precursor and the F127 / Resol composite micelle system, achieving uniform molecular-level dispersion and pre-assembly of multiple components in the solution, forming a stable precursor mixture solution.

[0043] Step 4: Template Immersion and Shaping: Transfer the mixed solution to a beaker containing 10 mL of sodium chloride (NaCl, particle size 50~100μm, optional particle size 50~200μm; the amount of NaCl is controlled to be 1.5~3 times the volume of the precursor solution), and let it stand for 3 hours to soak. Capillary action will allow the precursor solution to fully fill the three-dimensional porous network formed by the NaCl particles. Then, transfer the soaked mixture to a Buchner funnel lined with filter paper, connect a pressure-reducing pump, and squeeze out the excess solution under a negative pressure of 0.02 MPa (optionally below 0.03 MPa) to obtain a shaped light yellow solid "embryo".

[0044] Step 5, Curing Treatment: Transfer the light yellow solid preform to a crucible and place it in a 40℃ oven for 12 hours to completely remove volatile solvents. Then, raise the oven temperature to 100℃ and maintain it for 3 hours (optionally 2~4 hours) for curing treatment. This stage aims to promote the thermal crosslinking reaction of Resol to form a three-dimensional polymer skeleton with sufficient mechanical strength, providing a structural basis for subsequent high-temperature conversion.

[0045] Step 6, Inert Atmosphere Calcination: Under a nitrogen atmosphere (flow rate 50 mL / min, optional flow rate 50~100 mL / min), a programmed temperature rise heat treatment is performed at a rate of 1℃ / min: First, the temperature is held at 350℃ for 3h to achieve thermal decomposition and removal of the mesoporous template agent F127 and complete the initial carbonization of Resol to form an amorphous carbon skeleton; then the temperature is raised to 700℃ and held for 2h to promote further graphitization of the carbon support, and simultaneously achieve thermal reduction and interdiffusion alloying of platinum and iridium metal precursors, finally forming ultrafine and uniformly distributed Pt-Ir alloy nanoparticles.

[0046] Step 7, Template Removal and Drying: Remove the calcined gray solid and wash it repeatedly with deionized water 4 times (each wash using 5-10 times the mass of the solid sample) until no Cl is present in the washing solution. - The NaCl hard template was completely removed by detection (using silver nitrate solution); then the washed solid was placed in a vacuum drying oven and dried at 60℃ for 12h (or 60~80℃ for 6~12h) to obtain the ordered mesoporous nanosheet supported ultrafine Pt-based alloy catalyst Cat-1 (i.e. PtIr / SOMC).

[0047] Example 2 A method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst includes the following steps: Step 1, Preparation of Solution A: Weigh 0.1g of F127 and dissolve it in 5mL of THF solution. Disperse the solution by sonication at 100W for 20min. Add 2.0g of 20wt% Resol / THF solution and stir at room temperature for 10min to obtain Solution A. Step 2, Preparation of Solution B: Weigh 9 mg of Pt(acac)2 and 7 mg of Ir(acac)3, dissolve them in 10 mL of ethanol, stir at room temperature for 10 min to obtain yellow transparent solution B; Step 3: Preparation of precursor mixed solution: Pour solution A into solution B and stir at room temperature for 30 min to obtain precursor mixed solution; Step 4, Template soaking and molding: Pour the precursor mixture into a beaker containing 15 mL of NaCl solid (particle size 100~200 μm), soak for 3 h, transfer to a Buchner funnel, squeeze out excess solution under 0.01 MPa negative pressure to obtain a light yellow solid; Step 5, Curing treatment: Place the light yellow solid in a crucible, keep it in a 40℃ oven for 12 hours, and then raise the temperature to 100℃ and keep it for 4 hours. Step 6, Inert atmosphere calcination: Transfer the solid sample to a tube furnace, N2 flow rate 80 mL / min, heat to 350℃ at 1℃ / min and hold for 3h, then continue heating to 700℃ and hold for 2h. Step 7, Template Removal and Drying: Wash the solid 5 times with deionized water (each time the amount is 10 times the mass of the solid), and dry it under vacuum at 70℃ for 8 hours to obtain the target catalyst Cat-2.

[0048] Comparative Example 1 This comparative example is basically the same as Example 1, except that no filtration operation is performed.

[0049] Comparative Example 2 This comparative example is basically the same as Example 1, except that F17 is not added.

[0050] Comparative Example 3 This comparative example is basically the same as Example 1, except that Pt and Ir are not added, only mesoporous carbon is used.

[0051] Comparative Example 4 This comparative example is basically the same as Example 1, except that only the Pt precursor is added.

[0052] Comparative Example 5 This comparative example is basically the same as Example 1, except that only the Ir precursor is added.

[0053] Experimental Example 1: Structural Characterization of Catalysts The structures of the catalysts prepared in Examples 1 and 2 were examined using XRD diffraction, TEM, STM, and elemental mapping analysis. The results are as follows: Figures 1-5 As shown, the analysis is as follows: Figure 1 The XRD pattern of the ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst prepared in Example 1 is shown for analyzing the phase composition of the catalyst. Notably, no obvious, sharp characteristic diffraction peaks of elemental platinum (Pt) or iridium (Ir) are observed in the pattern. These XRD results preliminarily indicate that the present invention successfully obtained ultrafine Pt-Ir alloy particles using the described preparation method, and the extremely small particle size leads to a significant broadening of the diffraction peaks.

[0054] Figure 2 A 200 nm TEM image of the catalyst in Example 1 is shown. The image clearly shows that the catalyst exhibits a nanosheet morphology composed of interconnected thin sheets. More importantly, a highly ordered two-dimensional hexagonal mesoporous structure can be observed distributed throughout the nanosheet support. These pores are regularly arranged to form a continuous network. Simultaneously, numerous high-contrast black dots are visible in the image; these are the metal nanoparticles supported on the mesoporous carbon support. Even from the low-magnification image, it is evident that the metal particles are uniformly distributed, with no obvious large-scale aggregation, demonstrating the effectiveness of the method of this invention in achieving uniform dispersion of metal particles.

[0055] Figure 3 An STM image at the 100 nm scale of the catalyst in Example 1 is presented to further reveal its fine structure. This image more clearly shows the two-dimensional hexagonal arrangement of the ordered mesoporous channels, confirming its ordered mesoporous structure. The nanosheet morphology of the support is also more clearly defined. For the metal particles, their dispersion state can be observed more accurately at this scale, confirming that the particles are highly dispersed within the mesoporous framework and maintain good isolation from each other, which helps to expose more active sites.

[0056] Figure 4The elemental mapping analysis of the catalyst in Example 1 is presented. Using scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS), the distribution of carbon (C), platinum (Pt), and iridium (Ir) in the catalyst is visually demonstrated. The carbon signal is uniformly distributed, forming the catalyst support framework. Most importantly, the signal points representing Pt and Ir not only coexist uniformly throughout the entire nanosheet region, but their distribution profiles also highly overlap. This result provides strong evidence that Pt and Ir have a high degree of spatial consistency, strongly confirming the formation of a Pt-Ir alloy phase, rather than independent elemental particles.

[0057] Figure 5 High-resolution TEM images of the catalyst from Example 1 are shown to obtain the finest structural parameters. The lattice fringes of the metal particles are clearly visible in the images. By measuring and statistically analyzing the sizes of multiple particles, the average particle size was determined to be approximately 1.8 nm, falling into the category of ultrafine nanoparticles. Simultaneously, the images also clearly show the mesoporous channels on the support, with a measured pore size of approximately 3.2 nm. This matching relationship (ultrafine particles embedded in slightly larger mesopores) is beneficial for the stable anchoring of the metal particles, preventing migration and aggregation, and also ensures efficient mass transfer between reactant and product molecules. Nitrogen adsorption tests showed a specific surface area as high as 680 m². 2 / g.

[0058] Systematic characterization of the Cat-2 catalyst revealed that it successfully maintained an excellent ordered mesoporous nanosheet structure, indicating that the method of this invention still has strong structural controllability when faced with fluctuations in process parameters.

[0059] However, compared to Cat-1, the average particle size of Cat-2 alloy particles increased slightly to 2.2 nm, the mesopore size slightly expanded to approximately 3.8 nm, and the specific surface area was correspondingly adjusted to 620 m² / g. This phenomenon indicates that adjustments to process parameters can have a slight impact on the nanoconfining effect and crystal growth kinetics, but it remains within an acceptable range of excellent performance, further demonstrating that this preparation method has good process tolerance and flexibility.

[0060] The structure of the catalyst prepared in Comparative Example 1 without filtration is as follows: Figure 6As shown, the carbon framework exhibits severe shrinkage during soft template decomposition and pore wall crystallization, resulting in small mesopore sizes. The Pt / Ir alloy nanocrystals have a size of 6.29 nm and a wide distribution range. This is mainly due to the relatively thick liquid film adhering to the surface of the NaCl crystals during molecular assembly, and the weak interaction between the composite micelles and the NaCl salt, leading to significant aggregation of micelles during solvent evaporation. During high-temperature calcination, the reduced metals tend to migrate and aggregate, forming larger nanoparticles.

[0061] The structure of the catalyst (Pt / C) prepared without the addition of F17 in Comparative Example 2 is as follows: Figure 7 As shown, the absence of mesoporous structure and the relatively large particle size indicate that F127 helps control particle size and form an ordered mesoporous structure.

[0062] The structure of the catalyst (SOMC) prepared in Comparative Example 3 without the addition of Pt and Ir, containing only mesoporous carbon, is as follows: Figure 8 As shown, the pore size on the mesoporous carbon is ordered and exhibits a regular hexagonal shape.

[0063] The structures of the catalysts (Pt / SOMC) prepared by adding only Pt precursors in Comparative Example 4 are as follows: Figures 9-10 As shown, the particle size is 2.26 nm and the elemental distribution is uniform, indicating that the method in this scheme has universality.

[0064] The structures of the catalysts (Ir / SOMC) prepared by adding only Ir precursors in the five comparative examples are as follows: Figures 11-12 As shown, the particle size is 2.26 nm and the elemental distribution is uniform, indicating that the method in this scheme has universality.

[0065] Experimental Example 2: Application in the Anode Reaction of Ethanol Fuel Cells When Cat-1 (i.e., the PtIr / SOMC catalyst) was used in the anode reaction of a direct methanol fuel cell, it exhibited excellent catalytic activity and stability. Its methanol oxidation mass activity reached 1.2 A / mgPt, and after 5000 consecutive potential cycles, the activity retention rate remained at 85%, significantly better than conventional commercial Pt / C catalysts, demonstrating excellent resistance to poisoning and durability. Figure 13 ).

[0066] However, if a conventional catalyst (i.e., Pt / C) (or the Pt / SOMC catalyst prepared in Comparative Example 4) is used, the catalytic performance will rapidly decline due to Pt poisoning on the catalyst surface. Figure 14As shown, the performance of the commercial catalyst decreased by 89% after 1.45 hours, the catalyst prepared in Comparative Example 4 decreased by 80% after 45 hours, while the Cat-1 catalyst only decreased by 15% after 100 hours.

[0067] In summary, the comparative analysis of Examples 1 and 2 fully demonstrates that the preparation method provided by this invention possesses good reproducibility and significant flexibility in parameter control. Despite variations in key process conditions, the obtained catalysts (Cat-1 and Cat-2) exhibit significant advantages in terms of mesoporous structural order, metal dispersion, and overall catalytic performance. The superior performance of Cat-1 in electrocatalysis and the high efficiency and stability of Cat-2 in heterogeneous catalysis jointly indicate that the catalyst platform prepared by this method has broad applicability and can flexibly serve fuel cells, catalytic hydrogenation, and even other energy conversion and chemical reaction processes, providing a reliable technical path for the targeted design and controllable preparation of high-performance catalytic materials.

[0068] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst, characterized in that: Includes the following steps: Step 1, Preparation of Solution A: Dissolve F127 in THF solution, disperse by ultrasonication, add Resol / THF solution, and stir for 10 min to form a homogeneous solution A; Step 2, Preparation of solution B: Dissolve Pt(acac)2 and Ir(acac)3 together in ethanol and stir for 10 min to form a yellow transparent solution B; Step 3: Preparation of precursor mixed solution: Mix solution A and solution B, and stir at room temperature for 30 minutes to make them evenly mixed and form a homogeneous precursor solution; Step 4, Template Immersion and Shaping: Pour the thoroughly mixed precursor solution into a beaker containing NaCl solid and immerse it to allow the solution to fully penetrate the gaps between the NaCl solid. Filter under negative pressure to obtain a light yellow solid shaped by the NaCl template. Step 5: Curing treatment: After drying the light yellow solid at low temperature, heat the mixture to cure and set its shape; Step 6, Inert atmosphere calcination: The solidified solid sample is transferred to a tube furnace for calcination to obtain a gray solid; Step 7: Template removal and drying: Rinse the calcined gray solid repeatedly with deionized water to remove NaCl, and then vacuum dry to obtain the ordered mesoporous nanosheet supported ultrafine Pt-based alloy catalyst product.

2. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step one, the mass-to-volume ratio of F127, THF solution and Resol / THF solution is 0.1~0.5g:5~10ml:2~4.3g, and the mass fraction of Resol / THF solution is 20~35%; the ultrasonic dispersion time is 15~30min, and the power is 80~120W.

3. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step two, the mass-to-volume ratio of Pt(acac)2, Ir(acac)3 and ethanol is 9~37mg:7~15mg:10~25mL.

4. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step four, the NaCl crystals have a particle size of 50-200 μm and are used in an amount that is 1.5-3 times the volume of the precursor mixed solution.

5. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step four, the pressure of the negative pressure filtration is less than 0.03 MPa.

6. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step five, low-temperature drying involves slow drying in an oven at 40-60°C for 12-24 hours to completely evaporate solvents such as THF; the temperature-curing step involves heating to 100-130°C and maintaining the temperature for 2-4 hours to cure and set the shape.

7. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step six, the calcination is carried out in an N2 atmosphere with a heating rate of 1~5℃ / min, first heating to 350~450℃ for preheating and stabilizing for 3~5 hours, and then heating to 700~900℃ for high-temperature forging for 2~5 hours.

8. The method for preparing an ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 1, characterized in that: In step seven, the vacuum drying temperature is 60~80℃ and the time is 6~12h.

9. An ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst, characterized in that: The catalyst prepared by the method according to any one of claims 1 to 8 has a Pt-based alloy particle size of 1 to 3 nm, a mesopore size of 2 to 5 nm, and a specific surface area of ​​500 to 800 m². 2 / g.

10. The application of the ordered mesoporous nanosheet-supported ultrafine Pt-based alloy catalyst according to claim 9, characterized in that: The catalyst is used in fuel cells, catalytic hydrogenation reactions, or catalytic oxidation reactions of VOCs.

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