Ultrasmall intermetallic compounds confined in mesoporous carbon interstices and their preparation methods

Abstract

This invention belongs to the field of electrocatalytic hydrogen evolution catalyst technology, and particularly relates to an ultrasmall intermetallic compound confined in mesoporous carbon interstices and its preparation method. Using mesoporous silica SBA-15 as a hard template, sulfur-containing amino acids are filled into the SBA-15 channels via capillary action as a carbon source. Simultaneously, potassium chloroplatinate and a transition metal source are also filled into the SBA-15 channels along with the sulfur-containing amino acids. The mass ratio of potassium chloroplatinate, SBA-15, and sulfur-containing amino acids is 1:5–10:20–30, and the metal mass is consistent with the atomic ratio in the formed Pt-based intermetallic compound. The reaction also includes a solvent and water. This invention uses electrocatalytic hydrogen evolution as a model reaction to investigate the catalytic activity and stability of this PtFe ultrasmall nanoparticle embedded in a mesoporous carbon support. Electrocatalytic results show that it exhibits excellent activity and stability, meeting the requirements of related applications and development.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic hydrogen evolution catalyst technology, specifically relating to an ultrasmall intermetallic compound confined in mesoporous carbon interstices and its preparation method. Background Technology

[0002] Hydrogen (H2) is a promising energy carrier with a high energy density (120–142 MJ / kg). -1 When burned, H2 releases clean, pollution-free water. It is also an indispensable feedstock for some important modern chemical industries, including petroleum refining (such as hydrocracking and desulfurization) and ammonia production.

[0003] Currently, there are three main industrial methods for hydrogen production: steam methane reforming, coal gasification, and water electrolysis. Steam methane reforming and coal gasification both involve the consumption of fossil fuels, leading to severe environmental pollution and significant global warming. This key drawback contradicts the green vision of the hydrogen economy—powering the world through zero-carbon and pollutant-emission methods. Furthermore, other limitations of these two methods include low productivity and impurities in the produced H2, high energy consumption due to high pressure and temperature during production, and the requirement for sophisticated equipment. In contrast, H2 production via water electrolysis has long been a focus due to its low pollution, fast production speed, mild reaction conditions, and high purity (>99.999%).

[0004] In recent years, the rapid development of research on power generation using renewable energy sources (such as solar and wind power) has made the production of H2 through electrocatalytic hydrogen evolution reaction (HER) an attractive option, attracting widespread interest from academia and industry.

[0005] In the context of water electrolysis, overall catalytic activity can be improved by optimizing the electrocatalyst and electrolyte. Acidic electrolytes (e.g., H₂SO₄) are among the most effective electrolytes for electrocatalytic HER because they provide high concentrations of proton / hydrated hydrogen as reactants. Platinum-based noble metal catalysts exhibit high catalytic activity for HER under a wide pH range, but their high cost limits their large-scale application and increases the cost of hydrogen fuel.

[0006] With the rapid development of heterogeneous catalysis in chemical production, metal alloys formed between two or more metal elements through long-range chemical ordering and precise stoichiometry, also known as intermetallic compounds, have attracted increasing attention in catalysis. For example, Pt-based intermetallic compounds have shown highly enhanced oxygen reduction activity and durability. Furthermore, the formation of intermetallic compounds can further reduce the content of noble metals, lowering the cost of electrocatalytic hydrogen evolution devices. The performance of intermetallic compound catalysts depends on their composition, size, crystal structure, and fabrication. A fundamental issue for intermetallic compound catalysts is the stability of their surface structure under reaction conditions. Here, reaction conditions include not only gaseous / liquid reactants, pressure / concentration, and reaction temperature, but also the reaction medium, such as external stimuli like electrolytes with pH or potential (in electrocatalysis). Under external stimuli in the reaction environment, atomic arrangement and chemical composition undergo various changes, such as remodeling, segregation, sintering, disordering, and possible oxidation. These structural changes alter the electronic structure and surface adsorption properties, thus affecting the catalytic activity and stability of these nanocatalysts.

[0007] Constructing intermetallic compound catalysts with stable structures for continuous and efficient hydrogen evolution is crucial and a pressing scientific problem that needs to be solved. Summary of the Invention

[0008] To address the above technical problems, this invention provides an ultra-small intermetallic compound confined within mesoporous carbon interstices and its preparation method. The compound is a Pt-based intermetallic compound supported on mesoporous carbon. In a three-electrode system, this catalyst is used for the electrocatalytic hydrogen evolution reaction, exhibiting excellent catalytic activity and good stability.

[0009] The present invention, which addresses the above-mentioned technical problems, discloses an ultra-small intermetallic compound confined within mesoporous carbon interstices and its preparation method. The method is characterized by using mesoporous silica SBA-15 as a hard template, and filling the SBA-15 channels with sulfur-containing amino acids as carbon sources via capillary action. Simultaneously, potassium chloroplatinate and a transition metal source are also filled into the SBA-15 channels along with the sulfur-containing amino acids. The mass ratio of potassium chloroplatinate, SBA-15, and amino acids is 1:5–10:20–30, and the metal mass is consistent with the atomic ratio in the formed Pt-based intermetallic compound. The reaction process also includes a solvent and deionized water.

[0010] Various salts of transition metals can form intermetallic compounds with Pt. Although the relative molecular mass of each metal is different, the atomic ratio of Pt and M in the PtM intermetallic compound formed in this invention is fixed, so the amount of transition metal fed can be determined based on the content of Pt.

[0011] In the optimized scheme, the mass of potassium chloroplatinate is 8-12 mg, and the molar mass of the transition metal salt precursor is added according to the atomic ratio in the corresponding intermetallic compound; the mass of added SBA-15 is 40-120 mg, and the mass of sulfur-containing amino acids is 160-360 mg; in the further optimized scheme, the mass of potassium chloroplatinate is 8 mg, the mass of SBA-15 is 50 mg, and the mass of amino acids is 200 mg.

[0012] The transition metal source is one or more of cobalt salts, iron salts, manganese salts, copper salts, chromium salts, gallium salts, nickel salts, zinc salts, tin salts, and indium salts. In the optimized scheme, the transition metal source is one or more of ferric chloride, nickel chloride hexahydrate, cobalt nitrate hexahydrate, and copper nitrate hexahydrate.

[0013] The sulfur-containing amino acid is L-cysteine.

[0014] The solvent is ethanol, and in further optimization, it is anhydrous ethanol; the water is deionized water.

[0015] The hydrofluoric acid aqueous solution is a hydrofluoric acid aqueous solution with a mass concentration of 20%.

[0016] The ultrasmall intermetallic compounds include, but are not limited to, the following: binary PtFe, Pt3Fe, PtCo, Pt3Co, PtNi, PtNi3, Pt3Cr, Pt3Mn, PtZn, Pt3Zn, PtCu, PtCu3, Pt3In, PtSn, Pt3Sn, Pt3Ga; ternary PtCoMn, PtCoNi, PtFeMn, PtFeCo, PtFeCu, PtFeNi, PtCoCu, PtFeCr, PtCoCr, PtCuGa; quaternary PtFeNiCu, PtFeCoCu, PtNiCoCr, PtFeCoNi, PtFeCrCu, PtFeCrCu, PtFeNiCr, PtFeCoCr, PtPdCuGa; pentagonal: PtFeCoNiCu, PtFeCoCuCr, PtFeCoCuGa, PtFeCoNiCr or PtPdCuGaCr.

[0017] The present invention discloses a method for preparing an ultrasmall intermetallic compound confined within mesoporous carbon interstices, comprising the following steps:

[0018] (1) SBA-15 loaded with sulfur-containing amino acids and metal sources:

[0019] Potassium chloroplatinate was dissolved in deionized water to form solution A; the metal source was dissolved in anhydrous ethanol to form solution B; solutions A and B were added sequentially to SBA-15 and ground at room temperature until dry, then sulfur-containing amino acids were added and ground and mixed evenly into powder.

[0020] (2) Preparation of SBA-15-mesoporous carbon-supported Pt-based intermetallic compounds:

[0021] The powdered mixture in step (1) was placed in a tube furnace and calcined in a nitrogen / hydrogen stream using a three-stage programmed heating process to obtain SBA-15-mesoporous carbon-supported Pt-based intermetallic compound. The three-stage programmed heating process was as follows: the first stage was pyrolysis at 450-550℃ for 2-4 hours, the second stage was heated to 800-950℃ for 2-4 hours, and the third stage was cooled to 500-700℃ for 6-12 hours. The temperature change was determined according to the formation temperature of different intermetallic compounds. Finally, the temperature was lowered to room temperature to obtain SBA-15-carbon-supported Pt-based intermetallic compound.

[0022] In a reducing atmosphere, a series of ultra-small intermetallic compound catalysts confined within the interstices of mesoporous carbon are formed through a high-temperature annealing process. Benefiting from the anchoring effect of S on Pt in amino acids, small nanoparticle intermetallic compound catalysts are formed at high temperatures. Furthermore, these ultra-small nanoparticles can be embedded within the mesoporous carbon interstices, which greatly enhances the stability of the intermetallic nanoparticles.

[0023] (3) Preparation of mesoporous carbon-supported Pt-based intermetallic compounds:

[0024] The SBA-15 carbon-supported Pt-based intermetallic compound from step (2) was added to an aqueous hydrofluoric acid solution. After standing for 2 hours, the SBA-15 template was removed by centrifugation with deionized water. The washing was repeated three times to obtain the mesoporous carbon-supported Pt-based intermetallic compound.

[0025] After standing for 2 hours, wash with deionized water by centrifugation, i.e., etch for 2 hours at room temperature to remove SBA-15.

[0026] In step (2), the three-stage heating process is as follows: pyrolysis at 500-550℃ for 2-3 hours, followed by heating to 900℃ for 2-4 hours, and finally cooling down to 600℃ for 6-8 hours; in the optimized scheme, pyrolysis at 550℃ for 2 hours, followed by heating to 900℃ for 2 hours, and finally cooling down to 600℃ for 6 hours.

[0027] In the further optimized scheme, the heating rate of the first and second stages in step (2) is 2-5℃ / min, and the cooling rate of the third stage is 5-10℃ / min.

[0028] In step (3), the HF mass concentration used is 20%, and the number of repetitions is 3.

[0029] This invention uses thermodynamically stable SBA-15 as a template and sulfur-containing amino acids as a carbon source to fill the pores of SBA-15. Potassium chloroplatinate is used as the Pt source, and various types of metal salts serve as secondary metal sources. First, thanks to the strong interaction between S and Pt, the aggregation of Pt metal nanoparticles is successfully prevented under high-temperature conditions. The ultra-small intermetallic compound catalyst effectively improves the utilization efficiency of the metal active sites. Furthermore, the stable intermetallic crystal structure formed under high-temperature conditions further enhances catalytic stability. Finally, the mesoporous carbon, perfectly replicating the SBA-15 structure, provides a support for the intermetallic nanoparticles that resists strong acid and alkali corrosion. These ultra-small nanoparticles embedded in the mesoporous carbon support exhibit superior stability during catalysis.

[0030] Furthermore, compared to commercial Pt / C catalysts, the series of ultrasmall intermetallic compound catalysts confined within mesoporous carbon interstices in this invention, tested with PtFe as a model catalyst in electrocatalytic hydrogen evolution tests, exhibited excellent electrocatalytic activity and stability, and can be applied as cathode catalysts in industrial water electrolysis devices. Moreover, the preparation method of this invention is simple, rapid, and environmentally friendly, making it suitable for large-scale industrial production. Attached Figure Description

[0031] Figure 1 SEM image of the ultrasmall PtFe intermetallic compound confined by mesoporous carbon interstitials prepared in Example 1 of this invention.

[0032] Figure 2 TEM image of the ultrasmall PtFe intermetallic compound confined by mesoporous carbon interstitials prepared in Example 1 of this invention.

[0033] Figure 3 This is a high-magnification TEM image of the ultrasmall PtFe intermetallic compound confined within mesoporous carbon interstitials prepared in Example 1 of this invention.

[0034] Figure 4 The image shows the HAADF-STEM spectrum of the ultrasmall PtFe intermetallic compound confined by mesoporous carbon interstitials prepared in Example 1 of this invention.

[0035] Figure 5 XRD pattern of the ultrasmall PtFe intermetallic compound confined by mesoporous carbon interstitials prepared in Example 1 of this invention.

[0036] Figure 6 XRD pattern of the ultrasmall PtCo intermetallic compound confined by mesoporous carbon interstitials prepared in Example 2 of this invention.

[0037] Figure 7 The XRD pattern of the ultrasmall Pt3Co intermetallic compound confined by mesoporous carbon interstitials prepared in Example 3 of this invention.

[0038] Figure 8 Linear sweep voltammetry (LSV) curves (relative to RHE) of the ultrasmall PtFe intermetallic compound confined by mesoporous carbon interstitials prepared in Example 1 of this invention and commercial Pt / C as catalysts in 0.5 M H2SO4 aqueous solution.

[0039] Figure 9 The LSV curves (relative to RHE) of the ultrasmall PtFe intermetallic compound with mesoporous carbon interstitial confinement prepared in Example 1 of this invention are compared before and after 50,000 cyclic voltammetry (CV) cycles. Detailed Implementation

[0040] The ultrasmall intermetallic compounds obtained in this invention may include, but are not limited to, the following: binary PtFe, Pt3Fe, PtCo, Pt3Co, PtNi, PtNi3, Pt3Cr, Pt3Mn, PtZn, Pt3Zn, PtCu, PtCu3, Pt3In, PtSn, Pt3Sn, Pt3Ga; ternary PtCoMn, PtCoNi, PtFeMn, PtFeCo, PtFeCu, PtFeNi, P tCoCu, PtFeCr, PtCoCr, PtCuGa; quaternary PtFeNiCu, PtFeCoCu, PtNiCoCr, PtFeCoNi, PtFeCrCu, PtFeCrCu, PtFeNiCr, PtFeCoCr, PtPdCuGa; pentagonal: PtFeCoNiCu, PtFeCoCuCr, PtFeCoCuGa, PtFeCoNiCr or PtPdCuGaCr. The invention will be further described below with reference to specific embodiments:

[0041] Example 1

[0042] (1) SBA-15 loaded with amino acids and metal sources:

[0043] Dissolve 8 mg of potassium chloroplatinate and 8 mg of anhydrous ferric chloride in water and ethanol respectively, mix them in a mortar, add 50 mg of prepared SBA-15, and grind into powder. Then add 200 mg of L-cysteine ​​and grind evenly.

[0044] (2) Preparation of SBA-15-mesoporous carbon-supported PtFe intermetallic compound:

[0045] The ground powder mixture was placed in a tube furnace and calcined in a nitrogen / hydrogen stream using a three-stage programmed heating process to obtain SBA-15-mesoporous carbon-supported Pt-based intermetallic compound. The three-stage programmed heating process was as follows: pyrolysis at 500℃ for 2 hours at a heating rate of 2℃ / min, followed by heating to 800℃ for 2 hours at a heating rate of 2℃ / min, then cooling to 600℃ for 6 hours at a cooling rate of 5℃ / min, and finally cooling to room temperature to obtain SBA-15-carbon-supported PtFe intermetallic compound.

[0046] (3) Preparation of mesoporous carbon-supported PtFe intermetallic compounds:

[0047] The SBA-15 carbon-supported PtFe intermetallic compound from step 2 was added to a 20% hydrofluoric acid aqueous solution, allowed to stand for 2 hours, and then washed with deionized water by centrifugation to remove SBA-15. This washing process was repeated three times to obtain the mesoporous carbon-supported PtFe intermetallic compound. Figures 1-4 It is evident that mesoporous carbon perfectly replicates the ordered mesoporous channels of SBA-16, forming uniform and ultra-small nanoparticle PtFe intermetallic compounds within the inter-channel gaps. Figure 5 The X-ray diffraction (XRD) pattern further confirms the formation of a face-centered tetragonal intermetallic phase.

[0048] Example 2

[0049] (1) SBA-15 loaded with amino acids and metal sources:

[0050] Dissolve 8 mg potassium chloroplatinate, 5 mg ferric chloride, and 4 mg nickel chloride hexahydrate in water and ethanol, respectively. Mix them in a mortar and add 50 mg of prepared SBA-15. Grind into powder, then add 200 mg L-cysteine ​​and grind evenly.

[0051] (2) Preparation of SBA-15-mesoporous carbon-supported ternary Pt2FeNi intermetallic compound:

[0052] The ground powder mixture was placed in a tube furnace and calcined in a nitrogen / hydrogen stream using a three-stage programmed heating process to obtain SBA-15-mesoporous carbon-supported Pt-based intermetallic compound. The three-stage programmed heating process was as follows: pyrolysis at 500℃ for 2 hours at a heating rate of 2℃ / min, followed by heating to 900℃ at a heating rate of 2℃ / min for 2 hours, then cooling to 600℃ at a cooling rate of 5℃ / min for 6 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported ternary Pt2FeNi intermetallic compound.

[0053] (3) Preparation of mesoporous carbon-supported ternary Pt2FeNi intermetallic compounds:

[0054] The SBA-15-carbon-supported Pt2FeNi intermetallic compound from step 2 was added to a 20% hydrofluoric acid aqueous solution. After standing for 2 hours, it was washed with deionized water by centrifugation to remove SBA-15. This washing process was repeated three times to obtain the mesoporous carbon-supported ternary Pt2FeNi intermetallic compound. Figure 6 As can be seen, the X-ray diffraction (XRD) pattern confirms the formation of a Pt2FeNi structure with the P4 / mmm space group.

[0055] Example 3

[0056] (1) SBA-15 loaded with amino acids and metal sources:

[0057] Dissolve 8 mg potassium chloroplatinate, 3.6 mg ferric chloride, 5 mg cobalt nitrate hexahydrate, and 5 mg copper nitrate hexahydrate in deionized water and anhydrous ethanol, respectively. Mix them in a mortar and add 50 mg of the prepared SBA-15. Then grind into powder and add 200 mg of L-cysteine ​​and grind evenly.

[0058] (2) Preparation of SBA-15-mesoporous carbon-supported PtFeCoCu intermetallic compound:

[0059] The ground powder mixture was placed in a tube furnace and calcined in a nitrogen / hydrogen stream using a three-stage programmed heating process to obtain SBA-15-mesoporous carbon-supported Pt-based intermetallic compound. The three-stage programmed heating process was as follows: pyrolysis at 500℃ for 2 hours at a heating rate of 2℃ / min, followed by heating to 900℃ at a heating rate of 2℃ / min for 2 hours, then cooling to 600℃ at a cooling rate of 5℃ / min for 6 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported PtFeCoCu intermetallic compound.

[0060] (3) Preparation of mesoporous carbon-supported quaternary PtFeCoCu intermetallic compounds:

[0061] The SBA-15-carbon-supported quaternary PtFeCoCu intermetallic compound from step 2 was added to a 20% hydrofluoric acid aqueous solution. After standing for 2 hours, it was washed with deionized water by centrifugation to remove SBA-15. This process was repeated three times to obtain the mesoporous carbon-supported PtFeCoCu intermetallic compound. Figure 7 As can be seen, XRD proves that the atoms in the formed PtFeCoCu intermetallic compound are arranged in a P2tFeCu crystal structure with the space group Pm-3m.

[0062] Example 4

[0063] Other details are as described in Example 1, where mesoporous silica SBA-15 is used as a hard template. Sulfur-containing amino acids are filled into the pores of SBA-15 via capillary action as a carbon source. Simultaneously, potassium chloroplatinate and a transition metal source are also filled into the SBA-15 pores along with the sulfur-containing amino acids. The masses of potassium chloroplatinate, SBA-15, and amino acids are 8 mg, 40 mg, and 160 mg, respectively, and the metal mass corresponds to the atomic ratio in the formed Pt-based intermetallic compound. The reaction also includes a solvent and deionized water. The metal source is a cobalt salt or a chromium salt.

[0064] The three-stage heating process is as follows: pyrolysis at 450℃ for 2 hours at a heating rate of 5℃ / min, followed by heating to 900℃ at a heating rate of 5℃ / min for 2 hours, then cooling to 600℃ at a cooling rate of 8℃ / min for 8 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported PtCo / PtCr intermetallic compound.

[0065] Example 5

[0066] Other details are as described in Example 1, where mesoporous silica SBA-15 is used as a hard template. Sulfur-containing amino acids are filled into the pores of SBA-15 via capillary action as a carbon source. Simultaneously, potassium chloroplatinate and a transition metal source are also filled into the SBA-15 pores along with the sulfur-containing amino acids. The masses of potassium chloroplatinate, SBA-15, and amino acids are 8 mg, 80 mg, and 240 mg, respectively. The mass of the metal is consistent with the atomic ratio in the formed Pt-based intermetallic compound. The molar mass of the transition metal salt precursor is added according to the atomic ratio in the corresponding obtained intermetallic compound. The reaction also includes a solvent and deionized water. The metal source is a gallium salt or a nickel salt.

[0067] The three-stage heating process is as follows: pyrolysis at 550℃ for 4 hours at a heating rate of 3℃ / min, followed by heating to 900℃ at a heating rate of 3℃ / min for 4 hours, then cooling to 650℃ for 12 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported Pt3Ga / PtNi intermetallic compound.

[0068] Example 6

[0069] Other details are as described in Example 1, where mesoporous silica SBA-15 is used as a hard template. Sulfur-containing amino acids are filled into the pores of SBA-15 via capillary action as a carbon source. Simultaneously, potassium chloroplatinate and a transition metal source are also filled into the SBA-15 pores along with the sulfur-containing amino acids. The masses of potassium chloroplatinate, SBA-15, and amino acids are 8 mg, 64 mg, and 120 mg, respectively, and the metal mass corresponds to the atomic ratio in the formed Pt-based intermetallic compound. The reaction also includes a solvent and deionized water. The metal source is a manganese salt or a zinc salt.

[0070] The three-stage heating process is as follows: pyrolysis at 520℃ for 2.5h at a heating rate of 4℃ / min, followed by heating to 880℃ at a heating rate of 4℃ / min for 3h, then cooling to 550℃ at a cooling rate of 10℃ / min for 8h, and finally cooling to room temperature to obtain SBA-15-carbon-supported Pt3Mn / PtZn intermetallic compound.

[0071] Example 7

[0072] Other details are as described in Example 1, wherein the mass of potassium chloroplatinate is 8 mg, the molar mass of the transition metal salt precursor is added according to the atomic ratio in the corresponding obtained intermetallic compound, the mass of added SBA-15 is 40 mg, and the mass of sulfur-containing amino acids is 160 mg. The metal source is indium salt.

[0073] The three-stage heating process is as follows: pyrolysis at 500℃ for 2 hours at a heating rate of 2℃ / min, followed by heating to 900℃ at a heating rate of 2℃ / min for 2 hours, then cooling to 600℃ at a cooling rate of 6℃ / min for 6 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported Pt3In intermetallic compound.

[0074] Example 8

[0075] Other contents are as described in Example 1, wherein the molar mass of potassium chloroplatinate is 12 mg, the molar mass of the transition metal salt precursor is added according to the atomic ratio in the corresponding intermetallic compound, the mass of added SBA-15 is 120 mg, the mass of sulfur-containing amino acid is 360 mg, and the metal source is tin salt.

[0076] The three-stage heating process is as follows: pyrolysis at 520℃ for 2 hours at a heating rate of 3℃ / min, followed by heating to 900℃ at a heating rate of 3℃ / min for 3 hours, then cooling to 600℃ at a cooling rate of 7℃ / min for 10 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported PtSn intermetallic compound.

[0077] Example 9

[0078] Other contents are as described in Example 1, wherein the molar mass of potassium chloroplatinate is 10 mg, the molar mass of the transition metal salt precursor is added according to the atomic ratio in the corresponding intermetallic compound, the mass of added SBA-15 is 80 mg, the mass of sulfur-containing amino acid is 300 mg, and the metal source is copper salt.

[0079] The three-stage heating process is as follows: pyrolysis at 450℃ for 2 hours at a heating rate of 3℃ / min, followed by heating to 950℃ at a heating rate of 3℃ / min for 3 hours, then cooling to 600℃ at a cooling rate of 7℃ / min for 10 hours, and finally cooling to room temperature to obtain SBA-15-carbon-supported PtCu intermetallic compound.

[0080] Experiment 1

[0081] To demonstrate the beneficial effects of this invention, the mesoporous carbon interstitial confined ultrasmall PtFe intermetallic compound prepared in Example 1 was used as a catalyst and drop-coated onto the working electrode (area 0.07 cm²). -2 A three-electrode system consisting of a platinum-carbon electrode, a reference electrode Ag / AgCl, and a counter electrode graphite rod was used. The hydrogen evolution performance was tested in a 0.5 M H₂SO₄ aqueous solution using a linear sweep voltammetry method (5 mV / s). The results are shown in [Figure number missing]. Figure 8 .Depend on Figure 8 It can be seen that it is at 10 mAcm -2 At the specified current density, the overpotential is only 23 mV, higher than the 39 mV of commercial Pt / C catalysts, indicating significant potential for commercialization. Furthermore, 50,000 cyclic voltammetry (CV) tests were conducted using the above three-electrode system, and the results are shown below. Figure 9 .like Figure 9 As shown, after 50,000 CV cycles, at 10 mA / cm²... -2 At current density, the overpotential decreased by only 4 mV, demonstrating excellent hydrogen evolution stability.

[0082] This invention presents a series of binary to multi-component ultrasmall intermetallic compounds confined within mesoporous carbon interstices and their preparation methods. Using mesoporous silica SBA-15 as a hard template, sulfur-containing amino acids are filled into the SBA-15 channels via capillary action as a carbon source. Thanks to the strong interaction between S and Pt, the aggregation of Pt metal nanoparticles is successfully prevented under high-temperature conditions. The ultrasmall intermetallic compound catalyst not only effectively improves the utilization efficiency of the metal active sites, but the stable intermetallic crystal structure formed under high-temperature conditions has also been proven to be an important means of improving catalytic stability. Furthermore, the mesoporous carbon, which perfectly replicates the SBA-15 structure, provides a support for the intermetallic nanoparticles that resists corrosion by strong acids and bases. The catalytic activity and stability of these PtFe ultrasmall nanoparticles embedded in the mesoporous carbon support were investigated using electrocatalytic hydrogen evolution as a model reaction. Electrocatalytic results show that they exhibit excellent activity and stability, meeting the requirements of relevant applications and development.

[0083] The above embodiments / experimental examples are merely illustrative and not intended to limit the implementation methods. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementation methods. However, obvious variations or modifications derived therefrom remain within the scope of this invention.

Claims

1. A method for preparing ultrasmall intermetallic compounds confined within mesoporous carbon interstices, characterized in that: Using mesoporous silica SBA-15 as a hard template, sulfur-containing amino acids were filled into the pores of SBA-15 via capillary action as a carbon source. Simultaneously, potassium chloroplatinate and transition metal sources were also filled into the SBA-15 pores along with the sulfur-containing amino acids. The specific steps include the following: (1) SBA-15 loaded with amino acids and transition metal sources: Potassium chloroplatinate and transition metal salts were dissolved in water and ethanol, respectively. After mixing them in a mortar, SBA-15 was added and the mixture was ground into powder. Then, sulfur-containing amino acids were added and ground evenly. (2) Preparation of SBA-15-mesoporous carbon-supported Pt-based intermetallic compounds: The powdered mixture from step (1) was placed in a tube furnace and calcined in a nitrogen / hydrogen stream using a three-stage programmed heating process to obtain SBA-15-mesoporous carbon-supported Pt-based intermetallic compound. The three-stage programmed heating process was as follows: the first stage was pyrolysis at 450-550℃ for 2-4 hours, followed by the second stage of heating to 800-950℃ for 2-4 hours, and finally the third stage of cooling down to 500-700℃ for 6-12 hours, and finally the temperature was lowered to room temperature to obtain SBA-15-carbon-supported Pt-based intermetallic compound. (3) Preparation of mesoporous carbon-supported Pt-based intermetallic compounds: The SBA-15 carbon-supported Pt-based intermetallic compound from step (2) was added to an aqueous hydrofluoric acid solution, and after standing for 2 hours, it was washed with deionized water by centrifugation to remove SBA-15. This process was repeated three times to obtain the mesoporous carbon-supported Pt-based intermetallic compound.

2. The method for preparing ultrasmall intermetallic compounds confined in mesoporous carbon interstices according to claim 1, characterized in that: In step (2), the three-stage heating process is as follows: pyrolysis at 500-550℃ for 2-3 hours, followed by heating to 900℃ for 2-4 hours, and finally cooling down to 600℃ for 6-8 hours.

3. The method for preparing ultrasmall intermetallic compounds confined in mesoporous carbon interstices according to claim 2, characterized in that: In step (2), the three temperature-increasing processes are as follows: pyrolysis at 550℃ for 2 hours, followed by heating to 900℃ for 2 hours, and finally cooling down to 600℃ for 6 hours.

4. The method for preparing ultrasmall intermetallic compounds confined in mesoporous carbon interstices according to claim 1 or 2, characterized in that: In step (2), the heating rate in the first and second stages is 2-5℃ / min, and the cooling rate in the third stage is 5-10℃ / min.

5. The method for preparing ultrasmall intermetallic compounds confined in mesoporous carbon interstices according to claim 1, characterized in that: In step (3), the HF concentration used is 20%, and the washing is repeated 3 times.

6. The ultrasmall intermetallic compound prepared according to the method of claim 1, characterized in that: The mass ratio of potassium chloroplatinate, SBA-15, and sulfur-containing amino acids is 1:5-10:20-30, and the mass of the metals is consistent with the atomic ratio in the Pt-based intermetallic compound formed; the reaction also includes solvent and water.

7. The ultrasmall intermetallic compound according to claim 6, characterized in that: The mass of potassium chloroplatinate is 8-12 mg, and the molar mass of the transition metal salt precursor is added according to the atomic ratio in the corresponding intermetallic compound; the mass of SBA-15 added is 40-120 mg, and the mass of sulfur-containing amino acids is 160-360 mg.

8. The ultrasmall intermetallic compound according to claim 7, characterized in that: The mass of potassium chloroplatinate is 8 mg, the mass of SBA-15 is 50 mg, and the mass of amino acids is 200 mg.

9. The ultrasmall intermetallic compound according to claim 5 or 6, characterized in that: The transition metal source is one or more of the following: cobalt salt, iron salt, manganese salt, copper salt, chromium salt, gallium salt, nickel salt, zinc salt, tin salt, and indium salt.

10. The ultrasmall intermetallic compound according to claim 5, characterized in that: The sulfur-containing amino acid is L-cysteine.

11. The ultrasmall intermetallic compound according to claim 5, characterized in that: The ultrasmall intermetallic compounds include the following: binary: PtFe, Pt3Fe, PtCo, Pt3Co, PtNi, PtNi3, Pt3Cr, Pt3Mn, PtZn, Pt3Zn, PtCu, PtCu3, Pt3In, PtSn, Pt3Sn, Pt3Ga; ternary: PtCoMn, PtCoNi, PtFeMn, PtFeCo, PtFeCu, PtFeNi, PtCoCu, PtFeCr, PtCoCr, PtCuGa; quaternary: PtFeNiCu, PtFeCoCu, PtNiCoCr, PtFeCoNi, PtFeCrCu, PtFeNiCr, PtFeCoCr, PtPdCuGa; pentagonal: PtFeCoNiCu, PtFeCoCuCr, PtFeCoCuGa, PtFeCoNiCr or PtPdCuGaCr.

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