Carbon carrier encapsulated catalyst, its preparation method and application

Abstract

The application relates to a carbon carrier encapsulated catalyst and a preparation method and application thereof, relates to the technical field of fuel cells, and solves the problems that the key catalytic material of a proton exchange membrane fuel cell in the prior art seriously depends on noble metals, leading to high system cost, insufficient durability, easy deactivation of the existing Pt-based catalyst, a complicated preparation process and difficulty in stable bonding with a carbon carrier. The 1,3,5-tri (4-aminophenyl) benzene and an organic ligand monomer X are dissolved in acetonitrile, acetic acid is added, and the mixture is dispersed in N,N-dimethylformamide; iron nitrate solution, hydrogen peroxide and HAc are added to react; the mixture is dispersed in an ethanol aqueous solution, and a chloroplatinic acid hexahydrate aqueous solution and a cobalt chloride hexahydrate aqueous solution are added to obtain a precursor which is subjected to a reduction reaction, and then is subjected to acid washing to obtain the carbon carrier encapsulated catalyst; X includes triformylphloroglucinol, 1,4-dialdehyde-2,5-divinylbenzene and 1,3,5-tri (p-formylphenyl) benzene; and the catalyst is applied to the preparation of a proton exchange membrane fuel cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular to a carbon carrier encapsulated catalyst and a preparation method and application thereof. BACKGROUND

[0002] Proton exchange membrane fuel cell (PEMFC) is expected to become one of the core clean energy technologies for realizing the "carbon neutral" goal of future transportation and distributed energy systems due to its high energy conversion efficiency, environmental friendliness and fast start-up. However, the commercial application of current PEMFC is restricted by the fact that the key catalytic material is heavily dependent on noble metals, resulting in high system cost and insufficient durability. Although the current widely used platinum (Pt) based catalyst shows extremely high intrinsic activity in oxygen reduction reaction, due to the scarcity and high price of Pt resources, and the deactivation phenomena such as dissolution, migration and agglomeration of Pt during operation, the stability and economy of the catalyst are difficult to balance, thereby limiting the large-scale promotion of PEMFC.

[0003] To reduce the amount of Pt and improve the stability of the catalyst, researchers have proposed the method of alloying Pt catalyst, which forms Pt-M alloy with transition metals (such as Co, Ni, Fe, Cu, etc.), which can adjust the electronic structure and improve the oxygen reduction reaction activity. However, transition metals have poor chemical stability in acidic electrolyte, are easily dissolved or oxidized, leading to the destruction of the alloy structure and the degradation of the catalyst. Therefore, researchers gradually turned to the "encapsulation" strategy to stabilize alloy nanoparticles, that is, by taking advantage of the high electrical conductivity, structure adjustability and mechanical stability of carbon carriers, a composite structure with spatial confinement effect and strong metal-carrier interaction is constructed, thereby inhibiting nanoparticle migration, agglomeration and dissolution, and achieving a balance between high activity and high durability. For example, Professor Huang Yu's research group at the University of California, Los Angeles, reported a graphene nanopocket-encased PtCo@Gnp nanocatalyst (Graphene-nanopocket-encaged PtCo nanocatalysts for highly durable fuel cell operation under demanding ultralow-Pt-loading conditions, Nature Nanotechnology, 2022, 17, 968-975), which encapsulates ultrafine catalysts in non-contact graphene nanopockets, meets the electrochemical accessibility of the catalyst, limits catalyst coalescence and delays oxidation dissolution, diffusion and Ostwald ripening process, and improves the durability of the catalyst. But Co is easily dissolved in acidic environment, leading to unstable PtCo alloy phase structure, and thus affecting the catalyst life; at the same time, the preparation process is complex and the cost is high, which is not conducive to large-scale industrialization and application. In addition, the interface between the traditional carbon carrier and the alloy mainly depends on van der Waals force or weak electronic interaction, and it is difficult to form stable chemical coupling bond, so that the particles are easy to fall off or reconfigure in high potential cycle.

[0004] Therefore, in order to improve the above-mentioned defects, it is urgent to develop a catalyst with high durability, high stability and high noble metal utilization rate to improve the long-term durability and economic feasibility of proton PEMFC, maximize the utilization rate of noble metals and optimize the performance, provide a feasible path for reducing the cost of fuel cell system and prolonging the service life, and promote the large-scale application of PEMFC. SUMMARY

[0005] In order to solve the problems of the prior art proton exchange membrane fuel cell key catalyst material, such as serious dependence on noble metals, high system cost, insufficient durability, easy deactivation of existing Pt-based catalysts, complex preparation process, and difficulty in stable bonding with carbon carriers, the present application provides a carbon carrier encapsulated catalyst and its preparation method and application. The technical solution of the present application is as follows:

[0006] A preparation method of a carbon carrier encapsulated catalyst, comprising the following preparation steps:

[0007] S1: dissolving 1,3,5-tris(4-aminophenyl)benzene (TAPB) and an organic ligand monomer X in acetonitrile (ACN), adding acetic acid (HAc), evaporating the solvent, centrifuging, and drying to obtain TAPB-X-COF;

[0008] S2: dispersing TAPB-X-COF in N,N-dimethylformamide (DMF), adding an iron nitrate solution (Fe(NO3)3), hydrogen peroxide (H2O2), and HAc for reaction, and centrifuging to obtain TAPB-X-HCOF;

[0009] S3: dispersing TAPB-X-HCOF in an ethanol aqueous solution, adding an aqueous solution of hexahydrated chloroplatinic acid (H2PtCl6·6H2O) and an aqueous solution of hexahydrated cobalt chloride (CoCl2·6H2O), ultrasonic dispersion, stirring, and rotary evaporation to obtain a precursor; and performing a reduction reaction on the precursor under mixed gas protection, and acid washing and drying the reduction product to obtain a carbon carrier encapsulated PtCo@NC X catalyst;

[0010] The organic ligand monomer X is selected from one or a combination of at least two of benzene-1,3,5-tricarboxaldehyde (BTCA), 1,4-dialdehyde-2,5-divinylbenzene (DVA), and 1,3,5-tris(p-formylphenyl)benzene (TFPB).

[0011] Further, the molar ratio of TAPB to the organic ligand monomer X in S1 is 1:1; the concentration of HAc is 1-3 M, and the volume ratio of HAc to ACN is 1:20.

[0012] Further, the temperature for evaporating the solvent in S1 is 60°C, and the time for evaporating the solvent is 30 min; the centrifugation speed is 10,000 rpm, and the centrifugation time is 3 min; and the drying temperature is 60-80°C, and the drying time is 6-12 h.

[0013] Further, the volume ratio of N,N-dimethylformamide, the iron nitrate solution, hydrogen peroxide, and HAc in S2 is 10:1:1:1; the concentration of HAc is 1 M; the concentration of the iron nitrate solution is 50 mg / mL; and the mass fraction of hydrogen peroxide is 30%.

[0014] Further, the reaction temperature in S2 is 60°C, and the reaction time is 20 min; the centrifugation speed is 11,000 rpm, and the centrifugation time is 3 min.

[0015] Further, the mass ratio of platinum in the aqueous solution of chloroplatinic acid hexahydrate to cobalt in the aqueous solution of cobalt chloride hexahydrate in S3 is 100:8:0.81; the ultrasonic dispersion time is 30-40 min; the stirring time is 12 h; and the rotary evaporation temperature is 60 DEG C.

[0016] Further, the mixed gas in S3 is a mixture of argon and hydrogen, and the flow ratio of argon to hydrogen is 95:5; the reduction reaction conditions are as follows: heating to 250 DEG C at a heating rate of 5 DEG C / min, keeping for 2 h; continuously heating to 700 DEG C, keeping for 2 h, and cooling to room temperature.

[0017] Further, the pickling in S3 is carried out by using perchloric acid, and the pickling time is 12 h; and the drying temperature is 55 DEG C.

[0018] A carbon carrier encapsulated catalyst prepared by the above preparation method.

[0019] Application of the above carbon carrier encapsulated catalyst, applied to the preparation of a proton exchange membrane fuel cell.

[0020] Compared with the prior art, the present application solves the problems of the prior art proton exchange membrane fuel cell key catalytic material which is seriously dependent on noble metal, resulting in high system cost, insufficient durability, and the existing Pt-based catalyst which is easy to lose activity, has a complex preparation process, and is difficult to stably bond with the carbon carrier, and has the following specific beneficial effects:

[0021] 1. Significantly enhance the catalytic activity and mass activity: the present application uses TAPB and organic ligand monomer X (BTCA, DVA and TFPB) as the organic skeleton, synthesizes a hollow COF derived carbon carrier structure, and encapsulates Pt / Co alloy nanoparticles to construct a hollow COF derived carbon carrier-alloy nanoparticle synergistic structure system. The hollow COF derived carbon carrier has adjustable pore structure and high specific surface area, which effectively inhibits the migration and agglomeration of metal particles during high temperature treatment, improves the exposure degree and utilization rate of Pt atoms; at the same time, the hollow COF derived carbon carrier forms an effective physical protection for Ni / Co nanoparticles, ensures the long-term maintenance of active sites, significantly reduces the adsorption energy of oxygen intermediates in the catalytic reaction, and realizes the high-efficiency electrocatalytic performance of the catalyst under the condition of ultra-low Pt loading (0.1 mg Pt·cm -2 ), which provides an innovative path for the light weight and high efficiency of fuel cell catalysts.

[0022] 2. Significantly improve durability and anti-inactivation ability: The present application introduces nitrogen-doped carbon structure into the COF framework, forming two types of electronic regulation centers of pyridine nitrogen and graphite nitrogen. This structure design makes Pt transfer electrons to the nitrogen-doped carbon carrier with higher electronegativity, thereby forming stable Pt-N coordination bonds in the catalyst, significantly enhancing the electronic coupling effect between the carrier and the alloy particles, and effectively improving the charge transport efficiency of the catalyst. Thus, the technical defects of easy agglomeration, easy dissolution and rapid deactivation of the existing Pt-based catalyst are solved, ensuring the long-term reliability of the catalyst under actual operating conditions of fuel cells. The catalyst provided by the present application still retains a mass activity as high as 87.7% after 30000 stress cycle tests, and the voltage attenuation is only 8 mV, showing excellent electrochemical stability and structural integrity, providing strong technical support for the practical application and industrial development of fuel cell technology.

[0023] 3. Simple preparation process, reduce cost: The hollow COF derived carbon carrier is prepared by solvent evaporation method and high temperature pyrolysis method, and the preparation process is simple, the raw materials are easy to obtain and the cost is controllable; Pt / Co is introduced into the hollow carrier and encapsulated alloy nanoparticles are obtained after pyrolysis and acid washing treatment, the preparation path has good process repeatability and takes into account the high power density, low resistance and excellent durability of the catalyst, significantly reducing the consumption of noble metals and the preparation cost, providing a feasible catalyst material and process technology basis for balancing the system cost and performance improvement of fuel cells. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 PtCo@NC TAPBT Transmission electron micrograph of the catalyst, wherein, Figure 1 (a) is the TEM image of TAPB-BTCA-COF; Figure 1 (b) is the TEM image of TAPB-BTCA-HCOF; Figure 1 (c) is the TEM image of PtCo@NC TAPBT Catalyst at 200 nm magnification; Figure 1 (d) is the TEM image of PtCo@NC TAPBT Catalyst at 5 nm magnification;

[0025] Figure 2 X-ray diffraction spectrum of the catalyst;

[0026] Figure 3 X-ray photoelectron spectrum of the catalyst; wherein, Figure 3 (a) is the high-resolution XPS spectrum of the Pt 4f energy level in the catalyst; Figure 3 (b) is the high-resolution XPS spectrum of the N 1s energy level in the catalyst;

[0027] Figure 4 CV curve of the catalyst;

[0028] Figure 5 Accelerated aging curve of the catalyst;

[0029] Figure 6 Single cell polarization curve and power density curve of the catalyst under H2 / O2 conditions;

[0030] Figure 7 Single cell polarization curve and power density curve of the catalyst under H2 / Air conditions;

[0031] Figure 8 Single cell polarization curve and power density curve of the catalyst before and after aging test;

[0032] Figure 9 Pt and Co dissolution rate of the catalyst under different cycle numbers;

[0033] Figure 10 Oxygen proton transport resistance curve of the catalyst under single cell conditions;

[0034] Figure 11 Electrochemical impedance spectrum of the catalyst under single cell conditions. DETAILED DESCRIPTION

[0035] In order to make the technical solutions of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the specification of the present application. It should be noted that the following embodiments are only used to better understand the technical solutions of the present application, and should not be understood as a limitation of the present application.

[0036] Example 1.

[0037] S1: 28 mg of TAPB (0.08 mmol) and 13 mg of BTCA (0.08 mmol) were dissolved in 10 mL of ACN, 1 mL of HAc with a concentration of 1 M was added to initiate the Schiff base reaction until complete dissolution; the solution was placed in a 60℃ oven for 30 min, and the solvent was evaporated to dryness, centrifuged at a speed of 10000 rpm for 3 min, the yellow product was collected and washed with ethanol three times, and vacuum dried at 60℃ for 6 h to obtain TAPB-BTCA-COF;

[0038] S2: TAPB-BTCA-COF was dispersed in 20 mL DMF, 2 mL HAc, 2 mL Fe(NO3)3 ethanol solution with a concentration of 50 mg / mL and 2 mL 30% hydrogen peroxide aqueous solution were added in sequence; the mixed solution was placed in a 60°C oven for 20 min, and the imine bond was oxidized by ·OH generated by Fenton reaction to convert the synthesized COFs into HCOFs; the product was collected by centrifugation and washed with ethanol three times to obtain TAPB-BTCA-HCOF;

[0039] S3: 100 mg TAPB-BTCA-HCOF support was dispersed in a mixed solution of 50 mL ultrapure water and 5 mL ethanol for 30 min, 8.0 mg H2PtCl6·6H2O (7.4 mg Pt mL -1 ) solution and 0.81 mg CoCl2·6H2O (7.4 mg Co mL -1 ) solution were added, and the mixture was stirred for 12 h to make the metal source uniformly dispersed, and then rotary evaporation was performed at 60°C to obtain a precursor; the precursor was subjected to reduction reaction in a mixed gas of argon and hydrogen (Ar and H2 gas flow ratio was 95:5), and the temperature was raised to 250°C at a rate of 5°C / min, and maintained for 2 h, then the temperature was continuously raised to 700°C and maintained for 2 h, and then cooled to room temperature; the reduced product was ground into powder, washed with 0.1 M perchloric acid for 12 h, washed with deionized water by suction filtration, and dried in a 55°C oven overnight to obtain a black powder of PtCo@NC TAPBT catalyst.

[0040] The PtCo@NC TAPBT catalyst prepared in Example 1 was subjected to transmission electron microscopy (TEM) test, and the results are shown in Figure 1 , as shown in Figure 1 (a) is the TEM image of TAPB-BTCA-COF, which can present a regular spherical accumulation structure, uniform particle size and close distribution, and the surface morphology is relatively flat; Figure 1 (b) is the TEM image of TAPB-BTCA-HCOF, compared with TAPB-BTCA-COF, the edge of TAPB-BTCA-HCOF particles shows an obvious blurring trend, indicating that the organic framework has a carbon-based skeleton structure rich in micropores, which provides a good carrier basis for the subsequent loading of metal nanoparticles. As shown in Figure 1 (c) and (d) are TEM images of PtCo@NC TAPBT catalyst at different magnifications, from Figure 1 (c), it can be seen that PtCo nanoparticles are uniformly distributed on the surface of the carbon-based skeleton, and no obvious agglomeration phenomenon is observed, indicating that the metal precursor is effectively confined and uniformly grown during the carbonization process. FromFigure 1 As can be seen in (d), the PtCo nanoparticles are highly dispersed and the particle size is concentrated, with an average particle size of about 3.05 nm, and the lattice fringes are clearly distinguishable, with a spacing corresponding to the (111) crystal plane of the PtCo alloy. At the same time, a continuous carbon layer coating structure can be clearly observed on the surface of the nanoparticles, indicating that a nitrogen-doped carbon shell derived from COF is formed during the synthesis process, achieving effective encapsulation and protection of the metal particles.

[0041] Example 2.

[0042] S1: 28 mg of TAPB (0.08 mmol) and 22 mg of DVA (0.08 mmol) were dissolved in 10 mL of ACN, 4 mL of 1 M HAc was added to initiate the Schiff base reaction until complete dissolution; the solution was placed in a 60°C oven for 30 min, and the solvent was evaporated at a speed of 10000 rpm for 3 min, the yellow product was collected and washed with ethanol three times, and dried at 60°C under vacuum for 6 h to obtain TAPB-DVA-COF;

[0043] S2: TAPB-DVA-COF was dispersed in 20 mL of DMF, 2 mL of HAc, 2 mL of 50 mg / mL FeCl3 acetonitrile solution and 1 mL of 30% hydrogen peroxide aqueous solution were added in turn; the mixed solution was placed in a 60°C oven for 20 min, and the ·OH generated by Fenton reaction oxidized the imine bond, and the synthesized COFs were converted into HCOFs; the product was collected by centrifugation and washed with ethanol three times to obtain TAPB-DVA-HCOF;

[0044] S3: 100 mg of TAPB-DVA-HCOF carrier was dispersed in a mixture of 50 mL of ultrapure water and 5 mL of ethanol for 30 min, 8.0 mg of H2PtCl6·6H2O (7.4 mg Pt mL -1 ) solution and 0.81 mg of CoCl2·6H2O (7.4 mg Co mL -1 ) solution were added, and the mixture was stirred for 12 h to make the metal source uniformly dispersed, and then rotary evaporation was performed at 60°C to obtain a precursor; the precursor was subjected to reduction reaction in a mixed gas of argon and hydrogen (Ar and H2 gas flow ratio was 95:5), and the temperature was raised to 250°C at a rate of 5°C / min, and maintained for 2 h, then the temperature was further raised to 700°C and maintained for 2 h, and then cooled to room temperature; the reduced product was ground into powder, washed with 0.1 M perchloric acid for 12 h, washed with deionized water by filtration, and dried in a 55°C oven overnight to obtain a black powder of PtCo@NC TPDV catalyst.

[0045] Example 3.

[0046] S1: 28 mg TAPB (0.08 mmol) and 31.2 mg TFPB (0.08 mmol) were dissolved in 10 mL ACN and 10 mL chloroform. 4 mL of 1 M HAc was added to initiate the Schiff base reaction until completely dissolved. The solution was placed in a 60 °C oven for 30 min to evaporate the solvent. The solution was centrifuged at 10,000 rpm for 3 min, and the yellow product was collected and washed three times with ethanol. The product was then dried under vacuum at 60 °C for 6 h to obtain TAPB-TFPB-COF.

[0047] S2: Disperse TAPB-TFPB-COF in 20 mL DMF, then add 2 mL HAc, 2 mL of 50 mg / mL Fe(NO3)3 ethanol solution and 1 mL of 30% hydrogen peroxide aqueous solution sequentially; place the mixed solution in a 60℃ oven and react for 20 min. Through the ·OH oxide imine bond generated by the Fenton reaction, the synthesized COFs are converted into HCOFs; collect the product by centrifugation and wash it three times with ethanol to obtain TAPB-TFPB-HCOF;

[0048] S3: Disperse 100 mg TAPB-TFPB-HCOF carrier in a mixed solution of 50 mL ultrapure water and 5 mL ethanol, sonicate for 30 min, and add 8.0 mg H2PtCl6·6H2O (7.4 mg Pt mL). -1 ) solution and 0.81 mg CoCl2·6H2O (7.4 mg Co mL) -1 The solution was stirred for 12 h to ensure uniform dispersion of the metal source, and then rotary evaporated at 60 °C to obtain the precursor. The precursor was then subjected to a reduction reaction in a mixture of argon and hydrogen (Ar and H2 flow rates of 95:5), with the temperature increased to 250 °C at a rate of 5 °C / min and held for 2 h. The temperature was then further increased to 700 °C and held for 2 h before cooling to room temperature. The reduction product was ground into powder, acid-washed with 0.1 M perchloric acid for 12 h, filtered and washed with deionized water, and dried overnight in an oven at 55 °C to obtain a black powder, PtCo@NC. TPTF catalyst.

[0049] Comparative Example 1.

[0050] The difference between this comparative example and Example 1 is that step S2 is omitted, and the TAPB-BTCA-COF prepared in step S1 is directly applied to step S3 to prepare PtCo@NC. TAPBT -COF catalyst.

[0051] X-ray diffraction (XRD) tests were performed on the catalysts prepared in Examples 1-3, and the results are as follows: Figure 2 As shown, the catalyst exhibits distinct diffraction peaks at 2θ = 40.06°, 46.78°, 68.00°, 81.96°, and 86.24°, corresponding to the (111), (200), (220), (311), and (222) crystal planes of the face-centered cubic Pt structure, respectively. Compared with the standard Pt diffraction peak positions (39.76°, 46.24°, 67.45°, 81.29°, and 85.71°), each diffraction peak shows a slight positive shift, indicating a slight contraction in the lattice spacing. This positive shift is attributed to the formation of a solid solution alloy structure between Pt and Co, which has a smaller atomic radius, during pyrolysis. The introduction of Co atoms leads to a decrease in the lattice constant, thus verifying the successful formation of an alloy structure between Pt and Co. This result further demonstrates that the PtCo@NCTAPBT catalyst possesses typical Pt-Co alloy characteristics, providing a structural basis for its excellent electrochemical performance.

[0052] like Figure 3 The results shown are X-ray photoelectron spectroscopy (XPS) analysis of the catalysts prepared in Examples 1-3. Figure 3 (a) is the high-resolution XPS spectrum of the Pt 4f energy level in the catalyst. It can be seen from the figure that PtCo@NC TAPBT The catalyst exhibits typical Pt characteristics 0 With Pt 2+ Two valence state signals, located near 71 eV and 74 eV respectively, PtCo@NC TAPBT Pt 4f of the sample 7 / 2 With Pt 4f 5 / 2 The peak shifts by about 0.4 eV towards the direction of higher binding energy, indicating a decrease in Pt electron density and a significant electron transfer effect. Figure 3 (b) is the high-resolution XPS spectrum of the N 1s energy level in the catalyst. It can be seen from the figure that PtCo@NC TAPBT The significantly increased relative content of pyridine nitrogen and graphitic nitrogen in the catalyst indicates that nitrogen atoms are effectively incorporated into the carbon framework during pyrolysis, forming abundant coordination active sites that enable strong electronic coupling and chemical anchoring with metal atoms. The overall positive shift in Pt binding energy originates from electron transfer from Pt to the more electronegative N-doped carbon support. In particular, the Pt–N coordination bond formed with pyridine nitrogen induces electron redistribution at the interface, weakening the electron cloud density on the Pt surface and thus shifting the d-band center of Pt upwards. Moderate electron extraction helps optimize the adsorption strength of Pt for oxygen intermediates (·O, ·OH, ·OOH), ensuring that the binding with oxygen intermediates is within the ideal range, thereby effectively promoting the kinetics of the oxygen reduction reaction (ORR) and improving catalytic activity and overall battery performance.

[0053] To the solution containing 550 μL of isopropyl alcohol and 400 μL of water, 50 μL of a 5% mass fraction of Nafion solution was added, and then 5 mg of the PtCo@NC TAPBT , PtCo@NC TPDV and PtCo@NC TPTF catalysts prepared in Example 1-3 were added respectively, and ultrasonic dispersion was performed for 30 min to obtain a mixed solution; the above solution was drop-coated on a glassy carbon electrode to make the Pt loading on the glassy carbon electrode be 17 μg Pt cm -2 , and a thin film electrode was obtained after drying at room temperature; in a three-electrode system with a commercial hydrogen standard electrode as a reference electrode and a carbon rod as a counter electrode, cyclic voltammetry was performed in an oxygen-saturated 0.1 mol / L perchloric acid solution at a scanning speed of 10 mV / s; as shown in Figure 4 , it is the cyclic voltammogram of the catalyst in the perchloric acid solution, and it can be seen from the figure that the half-wave potential of the catalyst prepared in the application is significantly higher than that of the commercial Pt / C catalyst (0.88 V) with the same Pt loading, and the half-wave potential of the PtCo@NC TAPBT catalyst is 0.93 V. This is because the hollow COF-derived carbon carrier provided by the application provides a unique space confinement effect for the catalyst, which helps to prevent PtCo nanoparticles from aggregating during pyrolysis and effectively improves the utilization rate of Pt atoms, further enhances the catalytic activity of the oxygen reduction reaction, and thus exhibits excellent electrocatalytic activity.

[0054] The PtCo@NC TAPBT catalyst prepared in Example 1 was subjected to accelerated aging test, and the voltage was set to 0.6-1.0 V; as shown in Figure 5 , it is the accelerated aging curve of the catalyst in the perchloric acid solution, and it can be seen from the figure that after 50,000 cycles of cyclic scanning, the half-wave potential of the PtCo@NC TAPBT catalyst does not decrease significantly, while the half-wave potential of the Pt / C catalyst decreases by 99 mV; through the design of the hollow COF-derived carbon carrier, the PtCo alloy nanoparticles can be more uniformly dispersed on the carrier and the interaction between the metal and the carrier is enhanced, and the catalyst metal particles are effectively protected; such optimized electronic structure and metal-carrier interaction enable the PtCo@NC TAPBT catalyst to continuously maintain high activity in long-term operation, significantly improve the structural stability and corrosion resistance of the catalyst, and prevent the catalyst from degrading during operation, thereby enhancing its durability advantage in practical applications such as proton exchange membrane fuel cells.

[0055] The PtCo@NC TAPBTThe catalyst, used as the cathode catalytic layer in a single cell, has a Pt loading of 0.1 mg Pt cm⁻¹. -2 Using PtCo@NC TAPBT An ink mixture was prepared by mixing the catalyst with Nafion (5 wt%) in a 70:30 ratio. The ink mixture was ultrasonically treated for 1 h and then sprayed onto one side of a Nafion 211 ionomer membrane, with an effective area of ​​approximately 4 cm². 2 Until the cathode loading reaches 0.1 mgPt cm⁻¹ -2 Commercial Pt / C deposited carbon cloth (0.1 mg Pt cm⁻¹) was used at the anode. -2 This serves as the gas diffusion electrode (GDE). The membrane electrode assembly (MEA) operates at 80°C with a gas back pressure controlled at 0–2 atm, and hydrogen and oxygen flow rates of 300 sccm and 2000 sccm, respectively. Figure 6 The image shows PtCo@NC TAPBT The single-cell polarization and power density curves of the catalyst under H2 / O2 conditions are shown in the figures. As the current density increases, the cell voltage gradually decreases, while the power density first increases and then decreases, exhibiting typical fuel cell output characteristic curves. The peak power density of the PtCo@NCTAPBT single cell under H2 / O2 conditions reaches 2.30 W / cm². -2 This indicates that the present invention, through the design of a hollow COF support, optimizes the pore structure of the catalyst, significantly improves the diffusion rate of reactants, reduces mass transport resistance, and enables it to exhibit extremely high electrochemical activity and excellent oxygen reduction reaction kinetics. Figure 7 The figure shows the single-cell polarization and power density curves of the PtCo@NCTAPBT catalyst under H2 / Air conditions. The test conditions are the same as those shown. Figure 6 The results are largely the same, except that the cathode reaction gas is replaced with air at a flow rate of 2000 sccm. As shown in the figure, under air conditions, the polarization curve remains smooth and the voltage decay is relatively slow, indicating lower concentration polarization loss. The peak power density of the PtCo@NCTAPBT single cell under H2 / Air conditions remains as high as 1.23 W cm⁻¹. -2 The performance of this catalyst far exceeds that of conventional Pt / C electrodes under the same loading, indicating that the catalyst can still provide sufficient oxygen reduction activity in air and has significant mass activity, demonstrating excellent potential for practical applications.

[0056] PtCo@NC under MEA operating conditions TAPBTThe catalysts were tested under 30000 accelerated stress tests (AST) with a potential window set from 0.6 to 0.95 V; corresponding to the typical corrosion potential range of Pt. During the test, H2 was fed to the anode, and O2 and air were fed to the cathode, respectively, to evaluate the durability of the catalysts under different atmospheres. As shown in Fig. 1, the polarization curves and power density curves of the single cell before and after the catalyst aging test, it can be seen from the figure that, under H2 / O2 or H2 / Air conditions, the PtCo@NC catalysts showed a slight change in the polarization curve of the single cell, and the peak power density remained stable, indicating that the catalyst maintained a mass activity as high as 87.7% after 30000 cycles of AST, and the voltage decay was only 8 mV, maintaining excellent electrochemical stability and structural integrity, showing excellent long-term stability, durability and potential for practical application, far exceeding the initial mass activity target of the U.S. Department of Energy (DOE) in 2025 (0.44 A mgPt-1) and the DOE 2025 voltage decay target (voltage decay < 30 mV after 30000 cycles at 0.8 V). Figure 8 PtCo@NC TAPBT The polarization curves and power density curves of the single cell before and after the catalyst aging test, it can be seen from the figure that, under H2 / O2 or H2 / Air conditions, the PtCo@NC catalysts showed a slight change in the polarization curve of the single cell, and the peak power density remained stable, indicating that the catalyst maintained a mass activity as high as 87.7% after 30000 cycles of AST, and the voltage decay was only 8 mV, maintaining excellent electrochemical stability and structural integrity, showing excellent long-term stability, durability and potential for practical application, far exceeding the initial mass activity target of the U.S. Department of Energy (DOE) in 2025 (0.44 A mgPt-1) and the DOE 2025 voltage decay target (voltage decay < 30 mV after 30000 cycles at 0.8 V). TAPBT The polarization curves of the single cell catalysts hardly changed, and the peak power density remained stable, indicating that the catalyst maintained a mass activity as high as 87.7% after 30000 cycles of AST, and the voltage decay was only 8 mV, maintaining excellent electrochemical stability and structural integrity, showing excellent long-term stability, durability and potential for practical application, far exceeding the initial mass activity target of the U.S. Department of Energy (DOE) in 2025 (0.44 A mgPt-1) and the DOE 2025 voltage decay target (voltage decay < 30 mV after 30000 cycles at 0.8 V). -1 The polarization curves of the single cell catalysts hardly changed, and the peak power density remained stable, indicating that the catalyst maintained a mass activity as high as 87.7% after 30000 cycles of AST, and the voltage decay was only 8 mV, maintaining excellent electrochemical stability and structural integrity, showing excellent long-term stability, durability and potential for practical application, far exceeding the initial mass activity target of the U.S. Department of Energy (DOE) in 2025 (0.44 A mgPt-1) and the DOE 2025 voltage decay target (voltage decay < 30 mV after 30000 cycles at 0.8 V).

[0057] The PtCo@NC catalyst prepared in Example 1 TAPBT After each 10000 cycles of potential cycle test, 10 mL of test electrolyte was collected for inductively coupled plasma emission spectroscopy (ICP) analysis test to evaluate the metal dissolution behavior. As shown in Fig. 3, the Pt and Co element dissolution rate change curves of the catalyst under different cycle numbers, it can be seen from the figure that, under H2 / O2 or H2 / Air conditions, the PtCo@NC catalysts showed a slight change in the polarization curve of the single cell, and the peak power density remained stable, indicating that the catalyst maintained a mass activity as high as 87.7% after 30000 cycles of AST, and the voltage decay was only 8 mV, maintaining excellent electrochemical stability and structural integrity, showing excellent long-term stability, durability and potential for practical application, far exceeding the initial mass activity target of the U.S. Department of Energy (DOE) in 2025 (0.44 A mgPt-1) and the DOE 2025 voltage decay target (voltage decay < 30 mV after 30000 cycles at 0.8 V). Figure 9 The Pt and Co element dissolution rate change curves of the catalyst under different cycle numbers, it can be seen from the figure that, under H2 / O2 or H2 / Air conditions, the PtCo@NC catalysts showed a slight change in the polarization curve of the single cell, and the peak power density remained stable, indicating that the catalyst maintained a mass activity as high as 87.7% after 30000 cycles of AST, and the voltage decay was only 8 mV, maintaining excellent electrochemical stability and structural integrity, showing excellent long-term stability, durability and potential for practical application, far exceeding the initial mass activity target of the U.S. Department of Energy (DOE) in 2025 (0.44 A mgPt-1) and the DOE 2025 voltage decay target (voltage decay < 30 mV after 30000 cycles at 0.8 V). TAPBT The dissolution rate of the PtCo@NC catalyst was only 9.8%, which was significantly lower than that of the commercial Pt / C (31.2%). At the same time, the dissolution of Co element was also effectively inhibited, and the dissolution rate was limited to about 20.2%, which further indicated that the encapsulation structure of the PtCo@NC catalyst could significantly improve the structural stability and anti-dissolution ability of the alloy under harsh electrochemical cycle conditions, playing a key role in maintaining the alloy phase integrity and improving the durability of the catalyst. TAPBT The dissolution rate of the PtCo@NC catalyst was only 9.8%, which was significantly lower than that of the commercial Pt / C (31.2%). At the same time, the dissolution of Co element was also effectively inhibited, and the dissolution rate was limited to about 20.2%, which further indicated that the encapsulation structure of the PtCo@NC catalyst could significantly improve the structural stability and anti-dissolution ability of the alloy under harsh electrochemical cycle conditions, playing a key role in maintaining the alloy phase integrity and improving the durability of the catalyst.

[0058] To evaluate the impact of the hollow structure of the catalyst on the oxygen mass transfer process, the oxygen transport resistance (Rtot) of the catalyst layer in the MEA was quantitatively analyzed. Polarization curves were obtained using linear sweep voltammetry (LSV) under different back pressure conditions (0 atm, 0.5 atm, 1.0 atm, 1.5 atm, 2.0 atm), and Rtot was calculated by linear fitting of the current density at 0.1 V. Rtot consists of two parts: molecular diffusion resistance (RMD) and non-molecular diffusion resistance (Rnon-MD), with the relationship: Rtot = RMD + Rnon-MD. Based on the polarization curve fitting, as shown... Figure 10 PtCo@NC prepared in Example 1 TAPBT The oxygen proton transport conductance curve of the catalyst in a single cell shows that the hollow PtCo@NC catalyst prepared in Example 1... TAPBT The Rtot of the catalyst cathode is 69.91 S·m. -1 The results were significantly lower than those of the non-hollow PtCo@NC prepared in Comparative Example 1. TAPBT -COF catalyst (252.85 S·m) -1 This is also lower than the 90.63 S·m of commercial Pt / C catalysts. -1 This indicates that the introduction of the hollow structure significantly optimizes the gas diffusion channels and reaction interface microenvironment of the catalyst layer, effectively reduces oxygen transport resistance, and promotes the rapid transfer and utilization of reactants inside the electrode.

[0059] Electrochemical impedance spectroscopy (EIS) was performed in the MEA with a background voltage set to 0.8 V to analyze the electrode interface characteristics and oxygen transport behavior. Figure 11 The image shows PtCo@NC prepared in Example 1. TAPBT The EIS impedance diagram of the catalyst under single-cell conditions shows that, compared with the non-hollow PtCo@NC catalyst prepared in Comparative Example 1, it exhibits [significance / impedance]. TAPBT Compared to COF catalysts, PtCo@NC TAPBT The hollow structure of the catalyst exhibits a significantly reduced arc-shaped feature in the low-frequency region, indicating a significant reduction in oxygen transport resistance in the cathode layer. This demonstrates that the hollow structure of the catalyst provided by this invention effectively shortens the oxygen diffusion path in the catalyst layer, improves gas permeability and reactant transport efficiency, and simultaneously reduces charge and proton migration barriers. In summary, this invention uses TAPB and organic ligand monomers X (BTCA, DVA, and TFPB) as the organic framework to synthesize a hollow COF-derived carbon support structure and encapsulates Pt / Co alloy nanoparticles, constructing a hollow COF-derived carbon support-alloy nanoparticle synergistic structural system. This effectively inhibits the migration and aggregation of metal particles during high-temperature processing, achieving catalyst performance at ultra-low Pt loading (0.1 mg Pt·cm⁻¹).-2 The high efficient electrocatalytic performance, durability and anti-inactivation ability under the condition provide an innovative path for light weight and high efficiency of the fuel cell catalyst. Meanwhile, the preparation process of the application is simple, raw materials are easy to obtain and cost is controllable, which provides a feasible catalytic material and process technology foundation for reducing the cost of fuel cell system and improving the performance.

[0060] The above description of the embodiments is only used to help understand the method of the application and its core idea. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the application without departing from the principles of the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

[0061] The above description of the disclosed embodiments enables those skilled in the art to implement or use the application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a carbon support encapsulated catalyst, characterized by, The preparation method comprises the following steps: S1: dissolving 1,3,5-tris (4-aminophenyl) benzene and organic ligand monomer X in acetonitrile, adding acetic acid, evaporating the solvent, centrifuging, drying to obtain TAPB-X-COF; S2: dispersing TAPB-X-COF in N,N-dimethylformamide, adding iron nitrate solution, hydrogen peroxide and acetic acid to react, centrifuging to obtain TAPB-X-HCOF; S3: disperse TAPB-X-HCOF in an ethanol aqueous solution, add an aqueous solution of chloroplatinic acid hexahydrate and an aqueous solution of cobalt chloride hexahydrate, ultrasonic dispersion, stirring, rotary evaporation to obtain a precursor; the precursor is subjected to a reduction reaction under the protection of mixed gas, and the reduction product is subjected to acid washing and drying to obtain a carbon carrier encapsulated PtCo@NC X catalyst; The organic ligand monomer X is selected from one or a combination of at least two of benzene-1,3,5-tricarboxaldehyde, 1,4-dialdehyde-2,5-divinylbenzene and 1,3,5-tris (p-formylphenyl) benzene.

2. The method of claim 1, wherein the carbon support encapsulated catalyst is prepared by, The molar ratio of 1,3,5-tris (4-aminophenyl) benzene to the organic ligand monomer X in S1 is 1:1; the concentration of the acetic acid is 1-3 M, and the volume ratio of the acetic acid to the acetonitrile is 1:

20.

3. The method of claim 1, wherein the carbon support encapsulated catalyst is prepared by the steps of: The temperature for evaporating the solvent in S1 is 60°C, the time for evaporating the solvent is 30 min; the centrifugation speed is 10000 rpm, and the centrifugation time is 3 min; the drying temperature is 60-80°C, and the drying time is 6-12 h.

4. The method of claim 1, wherein the carbon support encapsulated catalyst is prepared by, The volume ratio of N,N-dimethylformamide, iron nitrate solution, hydrogen peroxide and acetic acid in S2 is 10:1:1:1; the concentration of the acetic acid is 1 M; the concentration of the iron nitrate solution is 50 mg / mL; and the mass fraction of the hydrogen peroxide is 30%.

5. The method of claim 1, wherein the carbon support-encapsulated catalyst is prepared by the steps of: The reaction temperature in S2 is 60°C, and the reaction time is 20 min; the centrifugation speed is 11000 rpm, and the centrifugation time is 3 min.

6. The method of claim 1, wherein the carbon support-encapsulated catalyst is prepared by the steps of: The mass ratio of TAPB-X-HCOF to platinum in the aqueous solution of chloroplatinic acid hexahydrate to cobalt in the aqueous solution of cobalt chloride hexahydrate in S3 is 100:8:0.81; the ultrasonic dispersion time is 30-40 min; the stirring time is 12 h; and the rotary evaporation temperature is 60°C.

7. The method of claim 1, wherein the carbon support-encapsulated catalyst is prepared by the steps of: The mixed gas in S3 is a mixture of argon and hydrogen, and the flow ratio of the argon to the hydrogen is 95:5; the reduction reaction conditions are as follows: heating to 250°C at a heating rate of 5°C / min and keeping for 2 h; continuously heating to 700°C and keeping for 2 h, and cooling to room temperature.

8. The method of claim 1, wherein the carbon support encapsulated catalyst is prepared by, The acid pickling in S3 is carried out by using perchloric acid, and the acid pickling time is 12 h; and the drying temperature is 55°C.

9. A carbon support encapsulated catalyst characterized by, Prepared by the preparation method in any one of claims 1-8.

10. Use of a carbon support encapsulated catalyst as claimed in claim 9, wherein, Applied to the preparation of a proton exchange membrane fuel cell.

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