Two-dimensional mesoporous silicon-based nanosheet as well as preparation method and application thereof in fuel cell
By combining graphene oxide templates with organic base catalysts, well-defined two-dimensional mesoporous silicon nanosheets were prepared, solving the problems of high cost and difficulty in morphology control in existing methods. This enabled the preparation of high-performance fuel cell catalysts and improved the stability and electrochemical performance of electrode materials.
Patent Information
- Application Number
- CN202511654860.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-02-17
AI Technical Summary
Existing methods for preparing two-dimensional mesoporous silicon nanosheets are costly and complex, making it difficult to achieve precise control over the product dimensions and morphology. This results in poor electrode material performance and cycling stability, and the formation of byproducts and pore structure collapse during the magnesian reduction process.
Using graphene oxide as a template, combined with nonionic surfactants and organic bases as structure directing agents and catalysts, two-dimensional mesoporous silicon nanosheets with regular mesoporous structures were prepared through sol-gel chemical reaction and pyrolysis process. Low-melting-point diluents and acid etching were used to avoid magnesium powder byproducts. Finally, the electronic structure was regulated by modifying elements.
The preparation of high-purity, structurally intact two-dimensional mesoporous silicon nanosheets has been achieved, which improves electron transport efficiency and catalytic stability, making them suitable for high-performance fuel cell catalyst supports and significantly enhancing the electrochemical performance of fuel cells.
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Figure CN121546076A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrocatalysis technology, specifically to a two-dimensional mesoporous silica-based nanosheet, its preparation method, and its application in fuel cells. Background Technology
[0002] Fuel cells, as devices that directly convert the chemical energy of fuel into electrical energy, possess outstanding advantages such as high energy conversion efficiency, zero or low emissions, and low noise, and are widely considered a key component of the future sustainable energy system. However, the commercialization of fuel cells (especially proton exchange membrane fuel cells) is still constrained by key issues such as the slow kinetics of the cathode oxygen reduction reaction and the high cost and insufficient stability of platinum-based catalysts.
[0003] Currently, the core bottleneck in fuel cell technology lies in the catalyst. Platinum and its alloys are currently the most efficient and irreplaceable catalyst materials for the oxygen reduction reaction; however, their scarcity, high price, and susceptibility to poisoning, aggregation, and loss during medium- and long-term operation severely limit the large-scale commercial application of fuel cells. Therefore, developing alternative catalysts with high activity, high stability, and low cost is a core task in promoting the development of fuel cell technology.
[0004] To address this issue, the scientific community has turned its attention to non-precious metal catalysts and carbon-based materials. Among them, silicon-based materials have shown great potential due to their abundant reserves, low cost, environmental friendliness, and unique semiconductor properties. However, bulk silicon materials have inherent drawbacks in electrocatalysis applications: firstly, their intrinsic conductivity is low, which is not conducive to the rapid transport of electrons; secondly, their specific surface area is limited, resulting in insufficient exposure of active sites; and thirdly, their chemical inertness makes them difficult to directly serve as highly efficient catalytic active centers.
[0005] To overcome these limitations, nanostructured silicon materials, especially mesoporous silicon and silicon nanosheets, have attracted widespread attention. Mesoporous structures can significantly increase the specific surface area of materials, providing more active sites; while fabricating silicon into two-dimensional nanosheet structures can effectively shorten the ion / electron transport paths and may produce novel physicochemical properties due to quantum confinement effects. Theoretically, combining the characteristics of "mesoporosis" and "two-dimensionality" to construct two-dimensional mesoporous silicon nanosheets holds promise for simultaneously achieving high specific surface area, high active site density, and rapid mass / charge transfer, making it an ideal structure for constructing high-performance silicon-based catalysts.
[0006] However, the preparation of two-dimensional mesoporous silicon nanosheets still faces significant challenges in existing technologies. Traditional methods for preparing silicon nanomaterials, such as chemical vapor deposition, are costly and complex; the magnesiac reduction method typically yields zero-dimensional particles, one-dimensional linear or amorphous bulk mesoporous materials, making it difficult to achieve precise control over the product's dimension and morphology. This also makes it prone to structural stacking and pore blockage, preventing the full realization of their potential electrocatalytic performance.
[0007] In summary, the main problems with existing methods for preparing two-dimensional mesoporous silicon are: (1) Existing methods mostly use bulk silicon as raw material, which is mostly irregular or two-dimensional in shape. The size of the mesoporous silicon prepared from this raw material is uncontrollable and the particles are in the micrometer range. When used to prepare electrode materials, the agglomeration is serious, the electrode materials are poor in performance, and the cycle stability of the electrode is not good; (2) In the process of magnesium thermal reduction, magnesium powder and other reducing agents are often used. The reaction is violent, a variety of by-products are produced, the reaction is incomplete, and the pore structure of the obtained powder collapses.
[0008] Therefore, developing a simple, cost-controllable, and scalable method for preparing two-dimensional mesoporous silicon-based nanosheets is of great significance for promoting the development of low-cost, high-performance fuel cells. Summary of the Invention
[0009] To address the aforementioned technical problems, this invention provides a method for preparing two-dimensional mesoporous silicon-based nanosheets and their applications.
[0010] The technical solution adopted in this invention is as follows: (1) Add graphene oxide to an aqueous solution containing a structure-directing agent and a catalyst, then sonicate and stir at a certain temperature to obtain a mixed solution; (2) Disperse the silicon source in the mixed solution obtained in step (1), stir the reaction at a certain temperature, and wash and freeze-dry the precipitate to obtain the graphene oxide-based mesoporous SiO2 composite material, denoted as GO-SiO2; pyrolyze GO-SiO2 in a certain atmosphere to obtain the mesoporous SiO2 material, denoted as m-SiO2. (3) The m-SiO2 material obtained in step (2) is mixed with a diluent, and then heat-treated under a certain atmosphere and cooled to room temperature to obtain a solid mixture; (4) The solid mixture obtained in step (3) is etched with acid, then washed with deionized water until neutral, and freeze-dried to obtain the two-dimensional mesoporous silicon-based nanosheet.
[0011] Preferably, in step (1), the structure directing agent is at least one of lauryl alcohol polyether-4, oleyl alcohol polyether-20, cetyl alcohol polyether-20 and fatty alcohol polyoxyethylene ether.
[0012] Nonionic surfactants such as lauryl alcohol polyether-4, oleyl alcohol polyether-20, cetyl alcohol polyether-20, and fatty alcohol polyoxyethylene ether have fundamental advantages over other structure-directing agents, such as hexadecyltrimethylammonium bromide. Common structure-directing agents like hexadecyltrimethylammonium bromide only act as catalysts to regulate reaction rates in material synthesis, mainly producing amorphous or dense silica. In contrast, the surfactants selected in this invention can form well-ordered micellar soft templates through molecular self-assembly, directly guiding the synthesis of mesoporous materials with large pore sizes, highly ordered pore channels, thicker pore walls, and stable structures. Their unique value lies in enabling fine structural design at the nanoscale, particularly providing a key technical pathway for the preparation of two-dimensional mesoporous structures, which cannot be achieved using only alkaline catalysts.
[0013] Preferably, in step (1), the catalyst is at least one of urea, tetramethylammonium hydroxide, ethylenediamine and pyridine.
[0014] The core advantage of using organic bases such as urea and tetramethylammonium hydroxide to replace traditional inorganic bases lies in achieving a leap from simply providing an alkaline environment to multifunctional synergistic control: these organic bases can not only catalyze hydrolysis and condensation reactions, but also completely volatilize after pyrolysis, completely eliminating metal contamination such as sodium ions, providing a high-purity material basis for fields such as microelectronics; at the same time, through the thermal decomposition of urea and its ammonia-reducing properties, the reaction kinetics can be precisely controlled, guiding uniform nucleation and ordered assembly, effectively optimizing the regularity and crystallinity of the mesoporous structure; in addition, their molecular structure can also act as a space filler and template agent in synergy, expanding the designability of special pore structures, ultimately improving the synthesis level simultaneously in three dimensions: material purity, structural precision, and functional diversity.
[0015] Preferably, in step (1), the mass ratio of graphene oxide, structure directing agent and catalyst is 1:(1-40):(0.2-3), the total mass of graphene oxide, structure directing agent and catalyst to the volume ratio of deionized water is 1g:(10-150)mL, the reaction temperature is 25-60℃, and the reaction time is 2-8h.
[0016] By controlling the proportion of each reactant in step (1), as well as the reaction temperature and reaction time, the self-assembly process of graphene oxide can be effectively regulated, thereby obtaining mesoporous materials with specific microstructures.
[0017] Preferably, in step (2), the silicon source is at least one of tetraethyl orthosilicate, methyl orthosilicate, sodium silicate, and hexenyl polydimethylsiloxane; the volume ratio of silicon source to mixed solution is 1:(1-40), the reaction temperature is 25-70℃, and the reaction time is 2-12h; the atmosphere is nitrogen, argon, helium, or carbon monoxide; the pyrolysis temperature is 300-650℃, and the pyrolysis time is 2-10h.
[0018] Compared to traditional silicon sources such as quartz sand and fumed silica, tetraethyl orthosilicate can undergo hydrolysis and condensation at room temperature via a sol-gel chemical reaction. Quartz sand, being chemically inert, requires physical melting at temperatures exceeding 1000 degrees Celsius for processing. Furthermore, the hydrolysis byproduct of tetraethyl orthosilicate is ethanol, which is easily removed and does not introduce impurity metal ions. Therefore, highly regular, uniformly sized mesoporous materials (such as MCM-41 and SBA-15) can be synthesized. Due to the less steric hindrance of the methoxy group (-OCH3) than the ethoxy group (-OC2H5), the hydrolysis and condensation rates of methyl orthosilicate are significantly accelerated, allowing for rapid gelation to fix specific structures or improve production efficiency. Sodium silicate, due to its extremely low cost, is the only suitable silicon source for industrial-scale production of hundreds of tons. Its aqueous solution is alkaline and can be directly used as a silicon source and alkaline catalyst, simplifying the process. Hexenyl polydimethylsiloxane is a high-molecular-weight polymer with a stable -Si-O- backbone structure. It is converted into a material through pyrolysis or chemical cross-linking. The terminal vinyl groups provide chemical reactivity, allowing for precise cross-linking or grafting of other functional molecules via hydrosilylation, enabling material design at the molecular level—a capability unmatched by small-molecule silicon sources. Furthermore, controlling the proportions of reactants directly determines the initial concentration of the sol, which is crucial for controlling the final material's pore structure and density. A high silicon source concentration results in a dense gel network, leading to a material with smaller pore sizes, lower pore volumes, and higher skeletal density after pyrolysis. Conversely, a highly diluted silicon source results in a looser gel network with larger interparticle spacing. Pyrolysis may yield lightweight materials with high specific surface area, large pore volume, and low density. However, excessively high concentrations may lead to insufficient structural strength and partial collapse.
[0019] Reaction temperature directly affects the rates of hydrolysis and condensation reactions, thus controlling the sol-gel process. A mild and slow reaction is beneficial for forming a gel with a uniform structure and few defects, but it requires a longer time. However, excessively high temperatures can significantly accelerate gelation and shorten the process cycle. But an overly rapid reaction may lead to uneven local cross-linking, resulting in a wider pore size distribution, or even phase separation. 70℃ is a commonly used upper limit; higher temperatures may lead to severe solvent evaporation or side reactions. The pyrolysis temperature range is crucial for achieving the carbonization of organic matter, the solidification of the inorganic framework, and the final formation of a porous structure. 300~500℃: This is the main thermal decomposition and cross-linking range for polymer frameworks (especially PDMS). At this temperature, organic groups (such as -CH3) gradually decompose to form amorphous carbon, while the siloxane backbone rearranges to form -Si-OC- or begins to form a SiC prototype. Too low a temperature results in incomplete carbonization. 500~650℃: Carbonization is basically complete, and the specific surface area and porosity of the material reach optimal values in this range. For ORR applications, the amorphous carbon defects formed at this temperature often exhibit good catalytic activity. Temperatures exceeding 650℃ may cause the carbon structure to begin transforming into a more ordered graphitization, resulting in a decrease in specific surface area, and premature sintering and densification may occur with certain silicon sources (such as TEOS). A reaction time of 2–12 hours is recommended to ensure sufficient hydrolysis-condensation reaction and the formation of a complete and stable gel network. Too short a time leads to incomplete pyrolysis, potentially leaving uncarbonized organic matter inside the material, resulting in poor conductivity and stability. Too long a time may cause excessive graphitization of the carbon framework or sintering collapse of the pore structure, which is detrimental to maintaining the porous structure and forming active sites. 2–10 hours is a reasonable window that ensures sufficient pyrolysis while avoiding overtreatment.
[0020] Preferably, in step (3), the diluent is at least one of sodium iodide, potassium iodide and magnesium oxide.
[0021] In the magnesothermic reduction process, sodium iodide, potassium iodide, or magnesium oxide are used as diluents, achieving a functional upgrade compared to traditional diluents such as sodium chloride / calcium chloride. Iodides, with their low melting point, can form a low-temperature molten salt medium, effectively reducing the reaction temperature and slowing down the exothermic rate, significantly improving the protection of heat-sensitive nanostructures (such as two-dimensional sheet-like morphologies). Magnesium oxide, as a solid diluent, precisely prevents nanosheet aggregation and structural collapse through rigid spatial confinement. Both diluents, through novel mechanisms of "low-temperature regulation" and "precise confinement," overcome the limitations of chlorides, which only provide basic "heat dissipation and isolation," and together provide dual protection for the structural integrity and high purity of two-dimensional nanomaterials.
[0022] Preferably, in step (3), the mass ratio of m-SiO2 material to diluent is 1:(1~12); the atmosphere is nitrogen, argon or hydrogen / argon mixture; the heat treatment temperature is 300~1200℃ and the time is 2~12h.
[0023] Preferably, in step (4), the acid used is at least one of hydrochloric acid, sulfuric acid and acetic acid.
[0024] In the process of removing by-products and etching holes, hydrochloric acid, sulfuric acid, or acetic acid are used instead of hydrofluoric acid or nitric acid. The core difference and advantage lies in significantly improving operational safety and structural compatibility while ensuring effectiveness. Specifically, hydrochloric acid and sulfuric acid, as strong acids, can efficiently dissolve metal oxide by-products while avoiding the high toxicity and corrosiveness of hydrofluoric acid, greatly reducing safety protection requirements. Acetic acid, on the other hand, achieves non-destructive treatment of pH-sensitive structures through its mild acidity, avoiding the chemical damage to the material surface caused by the strong oxidizing properties of nitric acid while preserving the intrinsic physicochemical properties of the products. This shift in acid systems represents a technological leap from "high risk / high activity" to "safe and controllable / structure-friendly," providing a better solution for the post-processing of precision nanostructures.
[0025] Preferably, in step (4), the acid treatment time is 0.5 to 8 hours and the temperature is 25 to 60°C.
[0026] A method for preparing two-dimensional mesoporous silicon-based nanosheets further includes: (5) The two-dimensional mesoporous silicon nanosheets obtained in step (4) are stirred and reacted with a solution containing modified elements. After washing with deionized water and freeze-drying, a solid mixture is obtained. (6) The solid mixture obtained in step (5) is heat-treated under a certain atmosphere and cooled to room temperature to obtain modified two-dimensional mesoporous silicon-based nanosheets.
[0027] Preferably, in step (5), the reaction solution used is one of ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, ferric chloride, and chloroplatinic acid.
[0028] Using salts such as ammonium fluoride and ammonium chloride, combined with pyrolysis, is a safer, more advanced, and more functional material modification strategy. It not only avoids the significant risks associated with directly using HF, HBr, etc., but also, through precise control of the etching process and the introduction of multifunctional components, can produce higher-quality, structurally superior two-dimensional composite materials with specific functions (such as catalysis and magnetism).
[0029] Preferably, in step (5), the solution containing the modified element is at least one of ammonium fluoride solution, ammonium chloride solution, ammonium bromide solution, ammonium iodide solution, ferric chloride solution and chloroplatinic acid solution.
[0030] Preferably, in step (5), the mass ratio of two-dimensional mesoporous silicon nanosheets to modified elements is 1:(10-25), the stirring reaction time is 6-24h, and the reaction temperature is 35-90℃. Preferably, in step (6), the atmosphere is nitrogen, argon or a mixture of hydrogen and argon; the heat treatment temperature is 450 to 850°C and the time is 4 to 10 hours.
[0031] This invention provides a two-dimensional mesoporous silicon-based nanosheet, which is prepared according to any one of the preparation methods in technical solutions 1 to 5.
[0032] This invention provides a modified two-dimensional mesoporous silicon-based nanosheet, which is prepared according to any one of the preparation methods in technical solutions 6 to 8.
[0033] This invention provides an application of the aforementioned two-dimensional mesoporous silicon-based nanosheets as a catalyst support for fuel cells.
[0034] This invention provides an application of the modified two-dimensional mesoporous silicon-based nanosheets as a cathode material for fuel cells.
[0035] The beneficial effects of this invention are: 1. This invention successfully circumvents the inherent defects of traditional magnesium thermal reduction methods, achieving a revolutionary improvement in product purity and a significant simplification of post-processing. In traditional methods, magnesium oxide byproducts generated after the reaction of magnesium powder adhere tightly to the product, requiring tedious and dangerous subsequent cleaning with strong acids. This process not only easily leads to the collapse of the material's mesoporous structure but also introduces magnesium ion contamination that is difficult to completely remove. This invention completely eliminates magnesium powder, using direct thermal reduction of graphene templates to prevent the generation of magnesium oxide byproducts at the source, thus omitting the strong acid cleaning step. This not only fully preserves the delicate and fragile structure of two-dimensional mesoporous silicon but also ensures that the final product is almost free of metallic impurities, laying a solid foundation for its application in microelectronic and energy devices where extremely high purity is required.
[0036] 2. This invention utilizes the two-dimensional planar properties of graphene and the vapor deposition effect to achieve precise and mild control over the morphology and structure of two-dimensional mesoporous silicon. Graphene itself serves as an ideal two-dimensional template, effectively guiding the nucleation and growth of silicon sources within its plane, thereby accurately replicating its sheet-like structure. Without the violent exothermic reaction of magnesium powder, the thermal reduction process is more gentle and controllable, effectively avoiding abnormal silicon grain growth, pore fusion, or structural sintering caused by localized overheating. This vapor-phase transport synthesis mechanism is conducive to the formation of two-dimensional mesoporous silicon nanosheets with uniform pore distribution, few lattice defects, and high structural integrity. Their excellent conductive network and abundant surface active sites enable them to exhibit electron transport efficiency and catalytic stability far exceeding those of traditional methods when used as a fuel cell catalyst support.
[0037] 3. This invention, through ingenious material design and modification strategies, successfully transforms readily available and inexpensive silicon into an advanced ORR electrocatalyst with high activity, high stability, and high conductivity. The introduction of highly electronegative elements such as fluorine, chlorine, bromine, and iodine effectively modulates the local electronic structure and charge distribution of the two-dimensional mesoporous silicon, reducing its adsorption energy barrier for oxygen molecules and reaction intermediates, thereby significantly accelerating the ORR reaction kinetics. In particular, co-doping with metals such as iron and platinum successfully constructs highly active site structures on the silicon substrate; these sites exhibit excellent intrinsic activity for ORR. Simultaneously, the synergistic effect of the mesoporous structure and surface modification ensures sufficient exposure of active sites and efficient mass transfer of reactants / products, further improving the overall catalytic efficiency. The subsequent thermal reduction step is crucial in this invention. This step effectively removes the insulating oxide layer on the material surface and repairs lattice defects, thereby significantly improving the intrinsic electronic conductivity of the two-dimensional mesoporous silicon material. This allows electrons to rapidly transfer from the active sites, meeting the requirements of high-speed electron transport in the ORR reaction and overcoming the core bottleneck of poor conductivity in traditional silicon materials. Attached Figure Description
[0038] Figure 1 XRD patterns of m-SiO2 and GO-SiO2 prepared in Example 1, and modified two-dimensional mesoporous silicon-based nanosheets prepared in Examples 2-6.
[0039] Figure 2 This is a SEM image of the GO-SiO2 material in Example 1.
[0040] Figure 3 This is a SEM image of the m-SiO2 material from Example 1.
[0041] Figure 4 This is a SEM image of the modified two-dimensional mesoporous silicon-based nanosheets from Example 2.
[0042] Figure 5 This is a TEM image of the modified two-dimensional mesoporous silicon-based nanosheets from Example 2.
[0043] Figure 6 The power density diagrams are for H2-O2 fuel cells using the two-dimensional mesoporous silicon nanosheet material of Example 1 and the modified two-dimensional mesoporous silicon-based nanosheets prepared in Examples 2-7.
[0044] Figure 7 This is a SEM image of the modified two-dimensional mesoporous silicon-based nanosheet material from Example 3.
[0045] Figure 8 This is a TEM image of the modified two-dimensional mesoporous silicon-based nanosheet material of Example 3.
[0046] Figure 9This is a SEM image of the modified two-dimensional mesoporous silicon-based nanosheet material from Example 4.
[0047] Figure 10 This is a SEM image of the modified two-dimensional mesoporous silicon-based nanosheet material from Example 5.
[0048] Figure 11 This is a SEM image of the modified two-dimensional mesoporous silicon-based nanosheet material from Example 6.
[0049] Figure 12 This is a SEM image of the modified two-dimensional mesoporous silicon-based nanosheet material from Example 7. Specific implementation methods
[0050] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments. Example 1
[0051] A two-dimensional mesoporous silicon-based nanosheet, the preparation method of which is as follows: S1: Synthesis of graphene oxide-based mesoporous silica wafers (GO-SiO2) using graphene oxide as a template: First, 0.35 g lauryl ether-4 and 0.05 g urea were dissolved in 62 mL of deionized water. Then, 0.2 g of graphene oxide was added to the above aqueous solution. After ultrasonic dispersion for 0.5 h, the solution was stirred at room temperature (25 °C) for 3 h to obtain a mixed solution.
[0052] S2: Add 42 mL of tetraethyl orthosilicate to the above mixed solution, react at 45 °C for 6 h, wash with deionized water until neutral, and freeze-dry to obtain GO-SiO2 material. XRD and SEM tests of the material are as follows. Figure 1 , Figure 2 As shown.
[0053] from Figure 1 It can be seen that this invention successfully synthesized GO-SiO2 material. Figure 2 It can be seen that the synthesized GO-SiO2 material has a two-dimensional nanosheet structure, and is uniformly dispersed without stacking.
[0054] S3: The GO-SiO2 material obtained in step S2 is heated to 350℃ in a nitrogen atmosphere and held at that temperature for 4 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding m-SiO2 material. The XRD and SEM tests of the material are as follows. Figure 1 , Figure 3 As shown.
[0055] from Figure 1 It can be seen that this invention successfully synthesized m-SiO2 materials. Figure 3It can be seen that the synthesized m-SiO2 material is a two-dimensional nanosheet structure, and it is uniformly dispersed without stacking.
[0056] S4: Mix 0.2g of m-SiO2 material obtained in step S3 with 0.65g of sodium iodide, then heat to 500℃ in a nitrogen atmosphere, keep the temperature constant for 4h, and then cool naturally to room temperature in an inert gas atmosphere to obtain the corresponding solid powder. S5: The solid powder calcined in step S4 is added to 20 mL of 1 M acetic acid solution, stirred at room temperature (25°C) for 1 h, then washed with deionized water until neutral, and freeze-dried to obtain two-dimensional mesoporous silicon nanosheet material. Example 2
[0057] A modified two-dimensional mesoporous silicon-based nanosheet A is prepared by the following method: S6: Add 0.1g of the two-dimensional mesoporous silicon material obtained in Example 1 to 100mL of 0.2M ammonium fluoride solution, stir for 12h at room temperature (25°C), wash with deionized water until neutral, and freeze dry to obtain the desired solid mixture; S7: The solid mixture obtained in step S6 is heated to 650°C in a nitrogen atmosphere and held at that temperature for 4 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding modified two-dimensional mesoporous silicon-based nanosheets A. Its XRD, SEM, and TEM tests are as follows: Figure 1 , Figure 4 and Figure 5 As shown.
[0058] from Figure 1 As can be seen, Example 2 successfully synthesized modified two-dimensional mesoporous silicon nanosheets. Figure 4 and Figure 5 It can be seen that the modified two-dimensional mesoporous silicon nanosheets A have thinner sheets, forming a rich mesoporous structure with uniform pore size, and the pores do not collapse or cross-link.
[0059] Fuel cell tests were conducted on the two-dimensional mesoporous silicon nanosheets prepared in Example 1 and the modified two-dimensional mesoporous silicon nanosheets A prepared in Example 2.
[0060] The experimental method is as follows: The test material was dispersed in an isopropanol / water / Nafion ion exchange resin (DuPont™ 20% Nafion solution) (14:5:1, volume ratio) to prepare cathode ink. Then, the cathode ink was injected at a concentration of 4 mg / cm³. 2The loading was sprayed onto a Nafion membrane (Nafion 212). For the anode, 40% Pt / C and Nafion ion exchange resin (I / C ratio of ion exchange resin to carbon was 0.8) were added to isopropanol to form an anode ink (3 mg / mL). The anode ink was sprayed onto the other side of the membrane, aligned with the cathode, to achieve a loading of 0.2 mg / mL. 2 The loading of Pt was determined. During spraying, the syringe flow rate was set to 100 μL / min, compressed air was used as the carrier gas, the nozzle pressure was set to 0.07 MPa, and the bottom heating plate was set to 80°C. All inks were ultrasonically dispersed in ice water for at least 2 hours before spraying. Waterproof carbon paper (Toray YLS-30T) with a microporous layer was used as the gas diffusion layer (GDL). The CCM was sandwiched between the GDL and hot-pressed at 120°C and 0.4 MPa for 3 minutes to form the membrane electrode assembly (MEA).
[0061] The experimental results are shown in Figure 6 ,from Figure 6 It can be seen that the power density of the unmodified two-dimensional mesoporous silicon nanosheets prepared in Example 1 is 0.33 W / cm². ‒2 It possesses certain properties and can be used as a catalyst support; the modified two-dimensional mesoporous silica-based nanosheet A prepared in Example 2 has a power density of 0.75 W / cm². ‒2 It has excellent fuel cell performance. Example 3
[0062] A modified two-dimensional mesoporous silicon-based nanosheet B is prepared by the following method: S1: Synthesis of graphene oxide-based mesoporous silica wafers (GO-SiO2) using graphene oxide as a template: First, 0.75g of oleyl alcohol polyether-20 and 0.12g of tetramethylammonium hydroxide were dissolved in 30mL of deionized water. Then, 0.3g of graphene oxide was added to the above aqueous solution. After ultrasonic dispersion for 0.5h, the solution was stirred at 40℃ for 2h to obtain a mixed solution.
[0063] S2: Then add 25 mL of tetraethyl orthosilicate to the above mixed solution, react at 30 °C for 6 h, wash with deionized water until neutral, and freeze dry to obtain the desired GO-SiO2 material.
[0064] S3: The GO-SiO2 material obtained in step S2 is heated to 450°C in a nitrogen atmosphere and kept at a constant temperature for 6 hours. Then it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding m-SiO2 material. S4: Mix 0.2g of m-SiO2 material obtained in step S3 with 0.55g of potassium iodide, then heat to 600℃ in a nitrogen atmosphere, keep at a constant temperature for 4h, and then cool naturally to room temperature in an inert gas atmosphere to obtain the corresponding solid powder. S5: The solid powder calcined in step S4 is added to 20 mL of 1 M nitric acid solution, stirred at 40 °C for 2 h, then washed with deionized water until neutral, and freeze-dried to obtain two-dimensional mesoporous silicon nanosheet material. S6: Add 0.1g of the two-dimensional mesoporous silicon material obtained in step S5 to 100mL of 0.2M ammonium chloride solution, stir at 45°C for 10h, wash with deionized water until neutral, and freeze dry to obtain the desired solid mixture. S7: The solid mixture obtained in step S6 is heated to 850°C in an argon atmosphere and held at that temperature for 6 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding modified two-dimensional mesoporous silicon-based nanosheets B. XRD, SEM, and TEM tests of the material are as follows: Figure 1 , Figure 7 and Figure 8 As shown.
[0065] from Figure 1 As can be seen, this embodiment successfully synthesized modified two-dimensional mesoporous silicon nanosheets. Figure 7 and Figure 8 It can be seen that the synthesized modified two-dimensional mesoporous silicon nanosheets B have thinner sheets, forming a rich mesoporous structure with uniform pore size, and the pores do not collapse or cross-link.
[0066] The modified two-dimensional mesoporous silicon-based nanosheets B prepared in Example 3 were tested in a fuel cell. The experimental results are shown in [Figure 3]. Figure 6 ,from Figure 6 As can be seen, the modified two-dimensional mesoporous silicon-based nanosheets B prepared in this embodiment have a power density of 0.86 W / cm². ‒2 It has excellent fuel cell performance. Example 4
[0067] A modified two-dimensional mesoporous silicon-based nanosheet C, the preparation method of which is as follows: S1: Synthesis of graphene oxide-based mesoporous silica wafers (GO-SiO2) using graphene oxide as a template: First, 0.3 g of agarol polyether-20 and 0.12 g of ethylenediamine were dissolved in 62 mL of deionized water. Then, 0.2 g of graphene oxide was added to the above aqueous solution. After ultrasonic dispersion for 0.5 h, the solution was stirred at 60 °C for 2 h to obtain a mixed solution.
[0068] S2: Then add 51 mL of tetraethyl orthosilicate to the above mixed solution, react at 70 °C for 8 h, wash with deionized water until neutral, and freeze dry to obtain the desired GO-SiO2 composite material.
[0069] S3: The GO-SiO2 composite material obtained in step S2 is heated to 650°C in a nitrogen atmosphere, kept at a constant temperature for 8 hours, and then naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding m-SiO2 material.
[0070] S4: Mix 0.2g of m-SiO2 material obtained in step S3 with 0.35g of sodium iodide and 0.2g of potassium iodide, then heat to 800℃ in a nitrogen atmosphere and keep at a constant temperature for 4h, then cool naturally to room temperature in an inert gas atmosphere to obtain the corresponding solid powder. S5: The solid powder calcined in step S4 is added to 20 mL of 1 M sulfuric acid solution, stirred at 40 °C for 3 h, then washed with deionized water until neutral, and freeze-dried to obtain two-dimensional mesoporous silicon nanosheet material. S6: Add 0.1g of the two-dimensional mesoporous silicon material obtained in step S5 to 100mL of 0.2M ammonium bromide solution, stir at 60°C for 20h, wash with deionized water until neutral, and freeze dry to obtain the desired solid mixture; S7: The solid mixture obtained in step S6 is heated to 850°C in a hydrogen / argon atmosphere and held at that temperature for 6 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding modified two-dimensional mesoporous silicon-based nanosheets C. The XRD and SEM tests of the material are as follows: Figure 1 and Figure 9 As shown.
[0071] from Figure 1 As can be seen, this embodiment successfully synthesized modified two-dimensional mesoporous silicon nanosheets. Figure 9 It can be seen that the synthesized modified two-dimensional mesoporous silicon nanosheets C have thinner sheets, forming a rich mesoporous structure with uniform pore size, and the pores do not collapse or cross-link.
[0072] The modified two-dimensional mesoporous silicon-based nanosheet material prepared in Example 4 was tested in a fuel cell. The experimental results are shown in [Figure 4]. Figure 6 ,from Figure 6 As can be seen, the power density of the modified two-dimensional mesoporous silicon-based nanosheet material prepared in this embodiment is 0.94 W / cm². ‒2 It has excellent fuel cell performance. Example 5
[0073] A modified two-dimensional mesoporous silicon-based nanosheet D, the preparation method of which is as follows: S1: Synthesis of graphene oxide-based mesoporous silica wafers (GO-SiO2) using graphene oxide as a template: First, 0.55g of fatty alcohol polyoxyethylene ether and 0.2g of pyridine were dissolved in 76mL of deionized water. Then, 0.2g of graphene oxide was added to the above aqueous solution. After ultrasonic dispersion for 0.5h, the solution was stirred at 55℃ for 6h to obtain a mixed solution.
[0074] S2: Then add 23 mL of tetraethyl orthosilicate to the above mixed solution, react at 65 °C for 12 h, wash with deionized water until neutral, and freeze dry to obtain the desired GO-SiO2 composite material.
[0075] S3: The GO-SiO2 composite material obtained in step S2 is heated to 400°C in a nitrogen atmosphere and kept at a constant temperature for 12 hours. Then it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding m-SiO2 material.
[0076] S4: Mix 0.2g of m-SiO2 material and 0.65g of magnesium oxide uniformly in step S3, then heat to 500℃ in a nitrogen atmosphere, keep the temperature constant for 4h, and then cool naturally to room temperature in an inert gas atmosphere to obtain the corresponding solid powder. S5: The solid powder calcined in step S4 is added to a mixed solution of 1M acetic acid and nitric acid in 20 mL, stirred at room temperature (25°C) for 1 h, then washed with deionized water until neutral, and freeze-dried to obtain two-dimensional mesoporous silicon nanosheet material. S6: Add 0.1g of the two-dimensional mesoporous silicon material obtained in step S5 to 100mL of 0.2M ammonium iodide solution, stir at 65°C for 24h, wash with deionized water until neutral, and freeze dry to obtain the desired solid mixture. S7: The solid mixture obtained in step S6 is heated to 700°C in an argon atmosphere and held at that temperature for 7 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding modified two-dimensional mesoporous silicon-based nanosheets D. The XRD and SEM tests of the material are as follows: Figure 1 and Figure 10 As shown.
[0077] from Figure 1 As can be seen, this embodiment successfully synthesized modified two-dimensional mesoporous silicon nanosheets. Figure 10 It can be seen that the synthesized modified two-dimensional mesoporous silicon nanosheets D have thinner sheets, forming a rich mesoporous structure with uniform pore size, and the pores do not collapse or cross-link.
[0078] The modified two-dimensional mesoporous silicon-based nanosheets D prepared in Example 5 were tested in a fuel cell. The experimental results are shown in [Figure 5]. Figure 6 ,from Figure 6As can be seen, the power density of the modified two-dimensional mesoporous silicon-based nanosheet material prepared in this embodiment is 1.17 W / cm². ‒2 It has excellent fuel cell performance. Example 6
[0079] A modified two-dimensional mesoporous silicon-based nanosheet E is prepared by the following method: S1: Synthesis of graphene oxide-based mesoporous silica wafers (GO-SiO2) using graphene oxide as a template: First, 0.35g lauryl ether-4, 0.12g fatty alcohol polyoxyethylene ether and 0.05g urea were dissolved in 68mL of deionized water. Then, 0.2g graphene oxide was added to the above aqueous solution. After ultrasonic dispersion for 0.5h, the solution was stirred at 60℃ for 3h to obtain a mixed solution.
[0080] S2: Then add 34 mL of tetraethyl orthosilicate to the above mixed solution, react at 45 °C for 6 h, wash with deionized water until neutral, and freeze dry to obtain the desired GO-SiO2 composite material.
[0081] S3: The GO-SiO2 composite material obtained in step S2 is heated to 650°C in a nitrogen atmosphere, kept at a constant temperature for 10 hours, and then naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding m-SiO2 material.
[0082] S4: The 0.2g m-SiO2 material obtained in step S3 is uniformly mixed with 0.65g potassium iodide and 0.12g magnesium oxidase, and then heated to 500℃ in a nitrogen atmosphere and kept at a constant temperature for 12h. Then it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding solid powder. S5: The solid powder calcined in step S4 is added to 20 mL of 0.6 M acetic acid solution, stirred at room temperature (25 °C) for 1 h, then washed with deionized water until neutral, and freeze-dried to obtain two-dimensional mesoporous silicon nanosheet material. S6: Add 0.1g of the two-dimensional mesoporous silicon material obtained in step S5 to 100mL of 0.2M ferric chloride solution, stir at 45°C for 24h, wash with deionized water until neutral, and freeze dry to obtain the desired solid mixture. S7: The solid mixture obtained in step S6 is heated to 850°C in an argon atmosphere and held at that temperature for 8 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain modified two-dimensional mesoporous silicon-based nanosheets E. XRD and SEM tests of the material are as follows: Figure 1 and Figure 11 As shown.
[0083] from Figure 1 As can be seen, this embodiment successfully synthesized modified two-dimensional mesoporous silicon nanosheets. Figure 11It can be seen that the synthesized modified two-dimensional mesoporous silicon nanosheets E have thinner sheets, forming a rich mesoporous structure with uniform pore size, and the pores do not collapse or cross-link.
[0084] The modified two-dimensional mesoporous silicon-based nanosheets E prepared in Example 6 were tested in a fuel cell. The experimental results are shown in [Figure 6]. Figure 6 ,from Figure 6 As can be seen, the power density of the modified two-dimensional mesoporous silicon-based nanosheet material prepared in this embodiment is 1.29 W / cm². ‒2 It has excellent fuel cell performance. Example 7
[0085] A modified two-dimensional mesoporous silicon-based nanosheet F is prepared by the following method: S1: Synthesis of graphene oxide-based mesoporous silica wafers (GO-SiO2) using graphene oxide as a template: First, 0.35g lauryl ether-4, 0.12g fatty alcohol polyoxyethylene ether and 0.05g urea were dissolved in 68mL of deionized water. Then, 0.2g graphene oxide was added to the above aqueous solution. After ultrasonic dispersion for 0.5h, the solution was stirred at 60℃ for 3h to obtain a mixed solution.
[0086] S2: Then add 34 mL of tetraethyl orthosilicate to the above mixed solution, react at 45 °C for 6 h, wash with deionized water until neutral, and freeze dry to obtain the desired GO-SiO2 composite material.
[0087] S3: The GO-SiO2 composite material obtained in step S2 is heated to 650°C in a nitrogen atmosphere, kept at a constant temperature for 10 hours, and then naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding m-SiO2 material.
[0088] S4: The 0.23gm-SiO2 material obtained in step S3 is uniformly mixed with 0.68g potassium iodide and 0.12g magnesium oxide, and then heated to 500℃ in a nitrogen atmosphere and kept at a constant temperature for 12h. Then it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding solid powder. S5: The solid powder calcined in step S4 is added to 20 mL of 0.6 M acetic acid solution, stirred at room temperature (25 °C) for 1 h, then washed with deionized water until neutral, and freeze-dried to obtain two-dimensional mesoporous silicon nanosheet material. S6: Add 0.1g of the two-dimensional mesoporous silicon material obtained in step S5 to 100mL of 0.2M chloroplatinic acid solution, stir at 45°C for 24h, wash with deionized water until neutral, and freeze dry to obtain the desired solid mixture. S7: The solid mixture obtained in step S6 is heated to 600°C in an argon atmosphere and held at that temperature for 8 hours. Then, it is naturally cooled to room temperature in an inert gas atmosphere to obtain the corresponding modified two-dimensional mesoporous silicon-based nanosheets F. The XRD and SEM tests of the material are as follows: Figure 1 and Figure 12 As shown.
[0089] from Figure 1 As can be seen, this embodiment successfully synthesized modified two-dimensional mesoporous silicon nanosheets. Figure 12 It can be seen that the synthesized modified two-dimensional mesoporous silicon nanosheets F have thinner sheets, forming a rich mesoporous structure with uniform pore size, and the pores do not collapse or cross-link.
[0090] The modified two-dimensional mesoporous silicon-based nanosheets F prepared in Example 7 were tested in a fuel cell. The experimental results are shown in [Figure 7]. Figure 6 ,from Figure 6 As can be seen, the power density of the modified two-dimensional mesoporous silicon-based nanosheet material prepared in this embodiment is 2.85 W / cm². ‒2 Compared to previously reported commercial platinum-carbon fuel cells, this exhibits superior fuel cell performance. The power density of commercial platinum-carbon fuel cells is typically 1.8–2 W / cm³. ‒2 .
[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. A method for preparing two-dimensional mesoporous silicon-based nanosheets, characterized by, The method comprises the following steps: (1) adding graphene oxide into an aqueous solution containing a structure-directing agent and a catalyst, then performing ultrasonic treatment, and stirring at a certain temperature to obtain a mixed solution; (2) dispersing a silicon source in the mixed solution obtained in step (1), stirring at a certain temperature, and washing and freeze-drying the precipitate to obtain a graphene oxide-based mesoporous SiO2 composite material, denoted as GO-SiO2; pyrolyzing the GO-SiO2 in a certain atmosphere to obtain a mesoporous SiO2 material, denoted as m-SiO2; (3) mixing the m-SiO2 material obtained in step (2) with a diluent, then performing heat treatment in a certain atmosphere, and cooling to room temperature to obtain a solid mixture; (4) etching the solid mixture obtained in step (3) with an acid, then washing to neutral with deionized water, and freeze-drying to obtain the two-dimensional mesoporous silicon-based nanosheet.
2. The production method according to claim 1, characterized by, In step (1), the structure-directing agent is at least one of lauryl polyether-4, oleyl polyether-20, cetyl polyether-20 and fatty alcohol polyoxyethylene ether; the catalyst is at least one of urea, tetramethylammonium hydroxide, ethylenediamine and pyridine; the mass ratio of graphene oxide, the structure-directing agent and the catalyst is 1:(1-40):(0.2-3), the volume ratio of the total mass of graphene oxide, the structure-directing agent and the catalyst to deionized water is 1 g:(10-150) mL, the reaction temperature is 25-60°C, and the reaction time is 2-8 h.
3. The production method and its use in fuel cells according to claim 1, characterized in that, In step (2), the silicon source is at least one of tetraethyl orthosilicate, methyl orthosilicate, sodium silicate and hexenyl polydimethylsiloxane; the volume ratio of the silicon source to the mixed solution is 1:(1-40), the reaction temperature is 25-70°C, the reaction time is 2-12 h; the certain atmosphere is nitrogen, argon, helium or carbon monoxide; the pyrolysis temperature is 300-650°C, and the pyrolysis time is 2-10 h.
4. The production method and its use in fuel cells according to claim 1, characterized in that, In step (3), the diluent is at least one of sodium iodide, potassium iodide and magnesium oxide; the mass ratio of the m-SiO2 material to the diluent is 1:(1-12); the certain atmosphere is nitrogen, argon or hydrogen / argon mixed gas; the heat treatment temperature is 300-1200°C, and the time is 2-12 h.
5. The preparation method according to claim 1, characterized in that, In step (4), the acid used is at least one of nitric acid, sulfuric acid and acetic acid; the acid treatment time is 0.5-8 h, and the temperature is 25-60°C.
6. The method of claim 1, wherein, Further comprising: (5) stirring the two-dimensional mesoporous silicon nanosheet obtained in step (4) with a solution containing a modification element, washing with deionized water, and freeze-drying to obtain a solid mixture; (6) heat-treating the solid mixture obtained in step (5) in a certain atmosphere, and cooling to room temperature to obtain a modified two-dimensional mesoporous silicon-based nanosheet.
7. The preparation method according to claim 6, characterized in that, In step (5), the solution containing a modification element is at least one of an ammonium fluoride solution, an ammonium chloride solution, an ammonium bromide solution, an ammonium iodide solution, a ferric chloride solution and a chloroplatinic acid solution; the mass ratio of the two-dimensional mesoporous silicon nanosheet to the modification element is 1:(10-25), the stirring reaction time is 6-24 h, and the reaction temperature is 35-90°C.
8. The preparation method according to claim 6, characterized in that, In step (6), the atmosphere is nitrogen, argon or hydrogen / argon mixture; the heat treatment temperature is 450-850℃, and the time is 4-10h.
9. A two-dimensional mesoporous silicon-based nanosheet, characterized in that, The method is prepared according to any one of claims 1-5.
10. A modified two-dimensional mesoporous silicon-based nanosheet, characterized in that, The method is prepared according to any one of claims 6-8.
11. Use of the two-dimensional mesoporous silicon-based nanosheets of claim 9 as a catalyst carrier for fuel cells.
12. Use of the modified two-dimensional mesoporous silicon-based nanosheets of claim 10 as a cathode material for fuel cells.