A low-platinum-based catalyst Pt-NC, its preparation method and application

Abstract

This application discloses a low-platinum-based catalyst Pt-N-C, its preparation method, and its application. The main steps are: S1, preparing COF precursor nanofiber materials; S2, preparing Pt... 2+ / COF composite material; S3, Pt 2+ The Pt / COF composite material is carbothermally treated under inert conditions to obtain a Pt-N-C catalyst supported on porous nanofibers by Pt nanoparticles and single-atom composite materials. This invention utilizes the synergistic effect of Pt nanoparticles and Pt single atoms to induce electron migration, effectively increasing electron cloud density and promoting rapid electron transfer during the reaction. This enhances the catalytic performance of the oxygen reduction reaction in acidic media. When used as a cathode catalyst in proton exchange membrane fuel cells, it exhibits higher power density and stability than commercial 20% Pt / C catalysts. This method is simple, cost-effective, easy to operate, and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell technology, specifically relating to a low-platinum-based catalyst Pt-NC, its preparation method, and its application. Background Technology

[0002] A hydrogen-oxygen fuel cell (HFC) is a clean and efficient energy device that uses oxygen as an oxidant and hydrogen as fuel. Through various chemical reactions of the fuel, the generated chemical energy is converted into electrical energy. HFCs differ significantly from conventional batteries. In conventional batteries, the active materials are stored internally, and the amount of stored active materials determines the battery's capacity. In HFCs, the active materials can be continuously supplied. Their greatest advantage is that they are not limited by the Carnot cycle, greatly improving energy utilization efficiency. Furthermore, fuel cells produce no carbon emissions or pollution, can be used for distributed power generation, have a relatively small size, low noise, and their power generation capacity can be increased by adding fuel, making them considered the most efficient device for utilizing hydrogen energy. The cathode oxygen reduction reaction, as the most important half-reaction in a fuel cell, has a slow kinetic reaction that severely affects fuel cell performance, thus requiring the use of highly active low-platinum-based catalysts. However, the natural reserves of platinum are very limited, and there is no fully mastered technology to replace platinum with non-precious metal catalysts. Proton exchange membrane fuel cells, due to their advantages such as low noise, low operating temperature, high energy conversion efficiency, and fast start-up speed, have attracted widespread attention in scientific research. Therefore, seeking efficient low-platinum-loading metal oxygen reduction electrocatalysts for application in the field of proton exchange membrane fuel cells has significant theoretical and practical implications.

[0003] In recent years, novel platinum-nitrogen-carbon (Pt-NC) electrocatalysts with abundant active centers on heteroatom-doped carbon nanosupports have been considered excellent and promising materials with high ORR catalytic activity. This is mainly because the ORR activity of these nitrogen-doped carbon matrix metal catalysts can be enhanced by utilizing their fully exposed metal active sites and maximum atom utilization efficiency. Covalent organic frameworks (COFs) are an emerging type of crystalline porous polymer with skeletal designability and precise structural tunability. Furthermore, COFs possess the inherent ability to anchor metals to N atoms, and through adsorption-pyrolysis strategies, COFs can be derived into NC and nanoscale porous channel carbon substrates with uniform MN centers. Some studies have shown that the coexistence of metal nanoparticles (NPs) and single atoms (SAs) can tune the electronic orbitals of MN active sites and facilitate O2 activation at these sites. Recent studies have shown that catalyst performance can be further enhanced by rationally customizing the electronic configuration of the active centers (e.g., the introduction of single atoms can tune the electronic structure of the metal clusters), the coordination environment (e.g., heteroatom coordination and coordination number), and the structure of the support (e.g., three-dimensional structure). Therefore, introducing Pt into N-COF-derived porous nanofibers via adsorption and pyrolysis processes yields a Pt-NC electrocatalyst, forming an NC substrate with a three-dimensional (3D) network structure supported by Pt single atoms, where graphene-coated Pt nanoparticles surround the Pt single atoms. This catalyst combines the high catalytic activity of Pt with the three-dimensional interwoven network of nanofibers and the abundant heteroatom doping sites of COF-derived NC, exhibiting high-quality activity, excellent cycle stability, and ORR performance. Its application in the efficient oxygen reduction reaction and as a cathode material for proton exchange membrane fuel cells is a wise strategy. Summary of the Invention

[0004] Technical problems to be solved:

[0005] This application addresses the technical problem that the slow kinetics of the oxygen reduction reaction in the cathode, the most important half-reaction in fuel cells, severely affects fuel cell performance. It provides a low-platinum-based catalyst, Pt-NC, its preparation method, and its applications. The method of this invention is simple, universal, and inexpensive. Furthermore, the resulting Pt-loaded nitrogen-doped carbon nanofiber material exhibits excellent activity and stability as an oxygen reduction electrocatalyst and good power density as a proton exchange membrane fuel cell cathode material.

[0006] Technical solution:

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0009] S1. Preparation of COF precursor nanofiber materials: Dissolve 50-300 mg of squaric acid in a mixed solvent of 3-20 mL toluene and 5-40 mL n-butanol and stir at 300-800 rpm for 10-300 min. Then add 100-600 mg of 1,3,5-tris(4-aminophenyl)benzene and heat and stir in an oil bath at 100-300 °C for 72-120 h under nitrogen atmosphere. Then wash with 10-60 mL n-butanol, 10-60 mL methanol and 10-60 mL tetrahydrofuran by centrifugation and dry at 40-100 °C to obtain COF precursor nanofiber materials.

[0010] S2, Preparation of Pt 2+ / COF composite material: Add 40-240mg of COF precursor nanofiber material to 15-80mL of acetonitrile solvent and stir. Then add 3-30mg of K2PtCl4 and continue stirring for 8-12h. After washing with 10-60mL of acetonitrile by centrifugation, dry it into powder at 70-90℃.

[0011] S3, Pt 2+ The / COF composite material is subjected to carbothermal treatment under inert conditions and then cooled to room temperature to obtain Pt-NC, a low-platinum catalyst supported on porous nanofibers, consisting of Pt nanoparticles and single-atom composite materials. The Pt single-atom material originates from the strong anchoring and dispersing effect between Pt and the amino and hydroxyl groups in COF, and is obtained in a single-atom form after calcination. The formation of Pt nanoparticles originates from the aggregation of Pt single-atom parts under high-temperature calcination conditions, ultimately forming a coexistence of Pt nanoparticles and single atoms.

[0012] Furthermore, the inert condition carbonization is carried out under a nitrogen atmosphere at a high temperature of 500–1000°C.

[0013] Furthermore, the high-temperature carbonization under a nitrogen atmosphere at 500–1000°C specifically involves heating to 500–1000°C at a rate of 1–20°C / min and holding at that temperature for 2–4 hours.

[0014] A low-platinum-based catalyst Pt-NC prepared by any of the above preparation methods, wherein platinum in the low-platinum-based catalyst Pt-NC is composed of two different forms: Pt nanoparticles and Pt single atoms.

[0015] This application also discloses the application of the low platinum-based catalyst Pt-NC in porous carbon nanofiber materials obtained after calcination.

[0016] This application also discloses the application of the low-platinum-based catalyst Pt-NC in the cathode material of proton exchange membrane fuel cells, wherein the low-platinum-based catalyst Pt-NC is supported on porous carbon nanofiber material as the cathode material in the proton exchange membrane fuel cell.

[0017] Furthermore, the centrifugation speed in S1 is 6000-12000 r / min.

[0018] Furthermore, the centrifugation speed in S2 is 6000-12000 r / min.

[0019] Furthermore, the loading method is an impregnation method.

[0020] This application also discloses the application of the low platinum-based catalyst Pt-NC in acidic oxygen reduction reaction catalysts.

[0021] The technical principle of this application is as follows: using potassium chloroplatinate as the metal source and squaric acid and 1,3,5-tris(4-aminophenyl)benzene as the carbon and nitrogen sources, a self-nitrogen-doped COF nanofiber material is pre-prepared through an in-situ condensation process. Platinum is adsorbed onto the COF by the adsorption of Pt ions onto the COF. Finally, under an inert environment, a high-temperature carbonization reduction treatment is performed to obtain nitrogen-oxygen-doped porous carbon nanofibers loaded with Pt nanoparticles and Pt single-atom materials. This material has a regular morphology, is multidimensional, and exhibits a 3D network interwoven structure. The Pt nanoparticles have a small size and are fixed within the interwoven carbon nanofibers by highly graphitized carbon.

[0022] Furthermore, the carbon nanofibers contain abundant N and O elements. Due to the synergistic effect and structural advantages between Pt nanoparticles, Pt single-atom active substances, and carbon nanofiber carriers, the resulting material exhibits high oxygen reduction activity and excellent stability under acidic conditions.

[0023] Beneficial effects:

[0024] This application provides a low-platinum-based catalyst Pt-NC, its preparation method, and its application. Compared with the prior art, it has the following advantages:

[0025] 1. Smaller Pt nanoparticles and uniformly dispersed Pt single-atom active materials exhibit excellent electrochemical activity and a greater number of catalytic active sites.

[0026] 2. The porous carbon nanofiber structure gives the catalyst material a large specific surface area, while the microporous structure of the carbon-based material can effectively promote the contact between the electrolyte and the catalyst, which is conducive to the reaction.

[0027] 3. Porous and highly graphitized carbon nanofiber matrix materials can effectively anchor active metal Pt nanoparticles, making them less prone to aggregation and detachment during the reaction process, which is beneficial to maintaining the integrity of the carbon composite structure.

[0028] 4. Squamous acid and 1,3,5-tris(4-aminophenyl)benzene with high nitrogen and oxygen content were selected as carbon and nitrogen sources. COF precursor materials were obtained in advance through condensation reaction. COF-derived carbon fiber supports with higher graphitization degree and better thermal stability were generated by high-temperature carbonization reduction. The incorporation of nitrogen and oxygen can effectively change the conductivity of carbon supports, thereby improving the electrocatalytic performance of materials.

[0029] 5. Nitrogen-oxygen-doped porous carbon nanofibers loaded with Pt nanoparticles and Pt single atoms are prepared by combining a simple and scalable in-situ condensation technique with high-temperature carbonization thermal reduction.

[0030] 6. The selected squaric acid and 1,3,5-tris(4-aminophenyl)benzene are inexpensive and readily available. Compared with traditional methods for preparing oxygen reduction electrocatalysts, this method is simple, cost-effective, easy to operate, and can achieve large-scale production.

[0031] 7. The obtained product has a regular morphology, and the Pt nanoparticles are stably supported in porous carbon nanomaterials. As a result, the prepared material has the characteristics of large specific surface area, many active sites, high half-wave potential, good stability, and multidimensional composite structure. Compared with conventional Pt-based catalyst materials, the prepared Pt-NC with porous carbon nanofiber material as support has superior structural characteristics and low cost. It is a very promising oxygen reduction electrocatalyst material, which shows good power density in proton exchange membrane fuel cells and is expected to have broad application prospects in the future energy industry. Attached Figure Description

[0032] Figure 1 This is a SEM image of the low-platinum-based catalyst Pt-NC prepared in Example 1 of this application as a cathode material for proton exchange membrane fuel cells;

[0033] Figure 2 This is a TEM image of the low-platinum-based catalyst Pt-NC prepared in Example 1 of this application as a cathode material for proton exchange membrane fuel cells;

[0034] Figure 3 This is the HR-TEM image of the low-platinum-based catalyst Pt-NC prepared in Example 1 of this application as a cathode material for proton exchange membrane fuel cells;

[0035] Figure 4This is the XRD pattern of the low-platinum-based catalyst Pt-NC prepared in Example 1 of this application as a cathode material for proton exchange membrane fuel cells;

[0036] Figure 5 LSV curve of the low platinum-based catalyst Pt-NC prepared in Example 1 of this application as a cathode material for proton exchange membrane fuel cells;

[0037] Figure 6 Tafel curves of the low-platinum-based catalyst Pt-NC prepared in Example 1 of this application as a cathode material for proton exchange membrane fuel cells;

[0038] Figure 7 The low-platinum-based catalyst Pt-NC prepared in Example 1 of this application is used for the polarization of the cathode material of a proton exchange membrane fuel cell and the corresponding power density curve;

[0039] Figure 8 The LSV curves of the materials obtained in Example 1 of this application are compared with those of Comparative Examples 1 and 2. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0041] Example 1:

[0042] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0043] S1. Preparation of COF precursor nanofiber material: 150 mg of squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then, 307 mg of 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then, the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0044] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0045] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0046] The Pt-NC catalyst materials prepared in Example 1 were physically characterized using SEM, TEM, HR-TEM, and XRD. Figure 1 As can be seen, this material is composed of a disordered, interwoven nanofiber structure. TEM image ( Figure 2 The images show that Pt nanoparticles are embedded in the surface and interior of porous carbon nanofibers, and this is evident in the HR-TEM images. Figure 3 The results show a high degree of graphitization on the surface of the carbon nanofibers, which are coated with Pt nanoparticles. This structure is consistent with the SEM results. Figure 4 The XRD pattern shows that the diffraction peaks of the material are completely consistent with the standard card of Pt (JCPDS card, 04-0802), proving the successful preparation of Pt nanoparticles and Pt single atoms. At the same time, the (002) crystal plane corresponds to the diffraction peak of graphitized carbon. Figure 5 This is the LSV curve obtained from oxygen reduction performance testing of the material. The curve shows that the initial reduction potential and half-wave potential are 1.01 V and 0.84 V, respectively. (Tafel curve) Figure 6 This indicates that the Tafel slope of this material is only 68.5 mV dec. -1 This is superior to most acidic oxygen reduction electrocatalyst materials. Figure 7 The polarization curves and corresponding power density curves of this material as a cathode material in a proton exchange membrane fuel cell show that the material has a high power density, with a maximum power density of 655.1 mW / cm². -2 The above results all indicate that this material has excellent application prospects as an alkaline oxygen reduction electrocatalyst.

[0047] Example 2:

[0048] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0049] S1. Preparation of COF precursor nanofiber material: 150 mg of squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then, 307 mg of 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then, the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0050] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then, 30mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0051] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0052] Example 3:

[0053] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0054] S1. Preparation of COF precursor nanofiber material: 200 mg squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then 307 mg 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0055] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0056] S3. Under nitrogen atmosphere, Pt 2+The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0057] Example 4:

[0058] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0059] S1. Preparation of COF precursor nanofiber material: 150 mg of squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then, 307 mg of 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then, the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0060] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 8h. The mixture was then washed with 20mL of acetonitrile by centrifugation and dried into powder at 70℃.

[0061] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0062] Example 5:

[0063] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0064] S1. Preparation of COF precursor nanofiber material: 150 mg squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then 307 mg 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 160 °C for 72 h under nitrogen atmosphere. Then the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0065] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 80℃.

[0066] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0067] Example 6:

[0068] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0069] S1. Preparation of COF precursor nanofiber material: 150 mg of squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then, 307 mg of 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then, the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0070] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 90℃.

[0071] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0072] Example 7:

[0073] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0074] S1. Preparation of COF precursor nanofiber material: 150 mg of squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then, 307 mg of 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then, the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0075] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0076] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 750℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0077] Example 8:

[0078] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0079] S1. Preparation of COF precursor nanofiber material: 150 mg squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 500 rpm for 10 min. Then 307 mg 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0080] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0081] S3. Under nitrogen atmosphere, Pt 2+The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0082] Example 9:

[0083] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0084] S1. Preparation of COF precursor nanofiber material: 150 mg squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then 307 mg 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then the mixture was washed by centrifugation with 20 mL n-butanol, 40 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0085] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0086] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 2h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0087] Example 10:

[0088] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0089] S1. Preparation of COF precursor nanofiber material: 150 mg squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then 307 mg 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 100 h under nitrogen atmosphere. Then the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0090] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 10mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0091] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 1h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0092] Comparative Example 1

[0093] A method for preparing a low-platinum-based catalyst Pt-NC specifically includes the following steps:

[0094] S1. Preparation of COF precursor nanofiber material: 150 mg of squaric acid was dissolved in a mixed solvent of 10 mL toluene and 20 mL n-butanol and stirred at 300 rpm for 10 min. Then, 307 mg of 1,3,5-tris(4-aminophenyl)benzene was added and heated and stirred in an oil bath at 120 °C for 72 h under nitrogen atmosphere. Then, the mixture was washed by centrifugation with 20 mL n-butanol, 20 mL methanol and 20 mL tetrahydrofuran respectively, and dried at 70 °C to obtain COF precursor nanofiber material.

[0095] S2, Preparation of Pt 2+ / COF composite material: 120mg of COF precursor nanofiber material was added to 40mL of acetonitrile solvent and stirred. Then 20mg of K2PtCl4 was added and stirred for 12h. The mixture was then washed by centrifugation with 20mL of acetonitrile and dried into powder at 70℃.

[0096] S3. Under nitrogen atmosphere, Pt 2+ The / COF composite material was heated to 850℃ at a heating rate of 5℃ / min and held at this temperature for 3h, and then cooled to room temperature to obtain the low platinum-based catalyst Pt-NC, in which Pt nanoparticles are supported on porous Pt single-atom nanofibers.

[0097] Comparative Example 2

[0098] The only difference between this comparative example and Example 1 is that platinum is not used; all other implementation conditions remain the same.

[0099] The LSV test results for the oxygen reduction reaction in the corresponding tests are as follows: Figure 8As shown, the metal-free electrocatalytic material exhibits the lowest onset reduction potential and the lowest half-wave potential, demonstrating the worst oxygen reduction performance. Both the metal-free COFs derivative NC electrocatalytic material and the commercial Pt / C material show inferior oxygen reduction performance compared to the Pt-NC material. The overall performance comparison shows the order Pt-NC > 20%Pt / C > Pt-NC-20 > NC, with Comparative Example 1 showing better performance than Comparative Example 2.

[0100] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a low-platinum-based catalyst Pt-NC, characterized in that, Specifically, the following steps are included: S1. Preparation of COF precursor nanofiber materials: Dissolve 50-300 mg of squaric acid in a mixed solvent of 3-20 mL toluene and 5-40 mL n-butanol and stir at 300-800 rpm for 10-300 min. Then add 100-600 mg of 1,3,5-tris(4-aminophenyl)benzene and heat and stir in an oil bath at 100-300℃ for 72-120 h under nitrogen atmosphere. Then wash with 10-60 mL n-butanol, 10-60 mL methanol and 10-60 mL tetrahydrofuran by centrifugation and dry at 40-100℃ to obtain COF precursor nanofiber materials. S2, Preparation of Pt 2+ / COF composite material: 40~240 mg of COF precursor nanofiber material was added to 15~80 mL of acetonitrile solvent and stirred. Then, 3~30 mg of K2PtCl4 was added and stirred for 8-12 h. After washing with 10~60 mL of acetonitrile by centrifugation, it was dried into powder at 70-90 °C. S3, Pt 2+ The / COF composite material is subjected to carbothermal treatment under inert conditions and then cooled to room temperature to obtain Pt-NC, a low-platinum catalyst supported on porous nanofibers, consisting of Pt nanoparticles and single-atom composite materials. The Pt single-atom material originates from the strong anchoring and dispersing effect between Pt and the amino and hydroxyl groups in COF, and is obtained in a single-atom form after calcination. The formation of Pt nanoparticles originates from the aggregation of Pt single-atom parts under high-temperature calcination conditions, ultimately forming a coexistence of Pt nanoparticles and single atoms.

2. The method for preparing a low-platinum-based catalyst Pt-NC according to claim 1, characterized in that, The inert conditions followed by carbothermic treatment involve high-temperature carbonization at 500-1000°C under a nitrogen atmosphere.

3. The method for preparing a low-platinum-based catalyst Pt-NC according to claim 2, characterized in that, The high-temperature carbonization under a nitrogen atmosphere at 500~1000℃ specifically involves heating to 500~1000℃ at a rate of 1~20℃ / min and holding at that temperature for 2~4 hours.

4. A low-platinum-based catalyst Pt-NC prepared by any one of the preparation methods of claims 1 to 3, characterized in that: In the low-platinum-based catalyst Pt-NC, platinum exists in two different forms: Pt nanoparticles and Pt single atoms.

5. The application of the low platinum-based catalyst Pt-NC as described in claim 4 in porous carbon nanofiber materials obtained after calcination.

6. The application of the low-platinum-based catalyst Pt-NC as described in claim 4 in the cathode material of a proton exchange membrane fuel cell, characterized in that: The low-platinum-based catalyst Pt-NC is supported on porous carbon nanofiber material as the cathode material in proton exchange membrane fuel cells.

7. The method for preparing a low-platinum-based catalyst Pt-NC according to claim 1, characterized in that: The centrifugation speed in S1 is 6000-12000 r / min.

8. The method for preparing a low-platinum-based catalyst Pt-NC according to claim 1, characterized in that: The centrifugation speed in S2 is 6000-12000 r / min.

9. The application according to claim 6, characterized in that: The loading method is the impregnation method.

10. The application of the low platinum-based catalyst Pt-NC as described in claim 4 in an acidic oxygen reduction reaction catalyst.

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