CN117638119A

CN117638119A - Catalyst for proton exchange membrane fuel cell and preparation method thereof

Info

Publication number: CN117638119A
Application number: CN202311663031.0A
Authority: CN
Inventors: 邢巍; 李宫; 刘长鹏; 肖梅玲; 金钊; 梁亮; 李晨阳; 王晨
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2023-12-06
Filing date: 2023-12-06
Publication date: 2024-03-01

Abstract

The invention relates to the technical field of fuel cells, in particular to a catalyst for a proton exchange membrane fuel cell and a preparation method thereof, and is characterized by comprising a packaging body formed by a nitrogen-containing carbon carrier and a Pt-based intermetallic compound; the nitrogen-containing carbon carrier is in a bowl-shaped structure and is used for packaging the Pt-based intermetallic compound; the Pt-based intermetallic compound includes Pt and at least one transition metal. According to the invention, by constructing the ultrathin bowl-shaped encapsulation body formed by the nitrogen-carbon-containing carrier and the Pt-based intermetallic compound, the pore network is constructed while the ionomer is prevented from poisoning the Pt-based alloy particles, so that a channel is provided for protons to reach the active sites of the Pt-based particles, and the stability and activity of the catalyst are effectively improved.

Description

Catalyst for proton exchange membrane fuel cell and preparation method thereof

Technical Field

The invention relates to the technical field of fuel cells, in particular to a catalyst for a proton exchange membrane fuel cell and a preparation method thereof.

Background

Proton Exchange Membrane Fuel Cells (PEMFC), also known as polymer electrolyte membrane fuel cells, are applied in the field of energy conversion devices as a promising candidate for clean energy solutions. The Membrane Electrode Assembly (MEA) at the core is generally composed of a catalyst, a proton exchange membrane, an ionomer and a gas diffusion layer, wherein a platinum (Pt) group metal (PGM) catalyst is a common catalyst choice in PEMFC construction due to its good electrocatalytic activity.

Pt is scarce in the earth and expensive, and in order to realize large-scale commercial application of PGM catalysts, the Pt loading must be reduced. However, when Pt loading is reduced, the active sites on the catalyst are correspondingly reduced, which results in a decrease in the efficiency of catalytic reactions on PGM catalysts. To alleviate the problems associated with Pt loading reduction, existing PGM catalyst options have improved from reducing catalyst size to form nanocatalysts, thereby achieving high ECSA (number of active sites per mass). However, nanoparticles with higher specific surface areas are thermodynamically less stable and are subject to significant size increases due to physical agglomeration and/or ostwald ripening processes.

Therefore, finding a catalyst for fuel cells that has high catalytic activity and high stability under extremely low Pt loading conditions is a key to the development of PEMFCs. Among these, carbon-based materials such as carbon nanotubes, graphene, etc., are widely used as carriers or auxiliary materials to improve the catalytic activity and stability of PGM catalysts due to their large specific surface area and good electrical conductivity.

The invention patent with publication number of CN114566661A provides a preparation method of platinum-cobalt nano particles loaded on the surface of a carbon material, and the invention utilizes N-N dimethylformamide to reduce platinum of a platinum precursor and cobalt of a cobalt precursor and uniformly disperse the cobalt on the inner holes and the surface of the carbon material, and then carries out heat treatment on the carbon material adsorbed with platinum and cobalt to remove carbon dangling bonds remained by oxygen groups on the surface or in the holes of the carbon material to capture metal single atoms, thus obtaining the catalyst of platinum-cobalt nano particles loaded on the surface of the carbon material.

In the case of using a carbon-based material as a catalyst carrier, the manner of interaction and structural composition of Pt-based alloy particles and the carbon-based carrier play a key role in the performance of the catalyst in a fuel cell. On the one hand, the direct contact of Pt-based alloy particles with the ionomer reduces the catalytic activity, and on the other hand, the overcoating of the carbon-based support results in proton and oxygen mass transfer losses during the Oxygen Reduction Reaction (ORR) due to the sulfonate groups of the ionomer poisoning the active sites on the catalyst surface. The catalyst with the platinum-cobalt nano particles loaded on the surface of the carbon material has a relatively simple preparation process, but the interaction mode of capturing metal single atoms through carbon suspension bonds between Pt-based alloy particles and a carbon carrier is not tight enough, the situation that the Pt alloy particles fall off or aggregate still occurs in the operation process of a fuel cell, and the catalytic performance and stability of the catalyst are still not ideal.

Disclosure of Invention

In order to solve the problems, the invention provides a catalyst for a proton exchange membrane fuel cell and a preparation method thereof, and the catalyst for the proton exchange membrane fuel cell obtained by the preparation method has the advantages of high catalytic activity and high stability.

In order to achieve the aim of the invention, the invention is realized by the following technical scheme:

in a first aspect, the present invention provides a catalyst for a proton exchange membrane fuel cell, characterized by comprising an encapsulation body formed by a nitrogen-containing carbon carrier and a Pt-based intermetallic compound; the nitrogen-containing carbon carrier is in a bowl-shaped structure and is used for packaging the Pt-based intermetallic compound; the Pt-based intermetallic compound includes Pt and at least one transition metal.

In the invention, the carrier structure of the nitrogen doped carbon can provide a strong metal-carrier effect, so that the bonding strength between Pt-based alloy particles and the carrier is improved, and migration agglomeration of Pt and carrier corrosion in the operation process of the fuel cell are effectively reduced. Meanwhile, constructing the multi-element Pt-based intermetallic compound is beneficial to regulating and controlling the electron orbit energy level distribution of Pt, and has positive significance for improving the structural stability of Pt-based alloy particles. Based on the above, the inventor finds that the thin bowl-shaped nitrogen-containing carbon carrier is constructed to encapsulate the Pt-based intermetallic compound, so that the active area attenuation of Pt can be reduced to the greatest extent, the poisoning of the ionomer on the nano particles is hindered, and the nitrogen-containing carbon carrier has pore channels which can directly reach the nano particles, so that the mass transfer process can be accelerated, and the catalytic activity is improved.

Preferably, the Pt-based intermetallic compound is a core-shell structure composed of a Pt-based skin layer and a Pt-based core.

Compared with a conventional Pt-based intermetallic compound structure, a core-shell structure with a synergistic effect of a Pt-based skin layer and a Pt-based core can be further formed in a package formed by the nitrogen-containing carbon carrier and the Pt-based intermetallic compound, and the core-shell structure has the stability of the Pt-based core with an ordered structure and the activity of the Pt-based skin layer. Inside the support pore channels of the bowl-like structure, the catalytic sites of the Pt-based alloy particles are not blocked by the ionomer but are immediately below the ionomer layer by the accessible porous carbon catalyst, further optimizing the mass transfer process and reducing mass transfer resistance. Catalysts having a core-shell structure exhibit high activity and stability over most current technologies during actual operation of fuel cells.

Preferably, the Pt-based skin layer is PtCo and the Pt-based core is Pt ₃ Co。

High stability Pt ₃ The ordered core-shell structure formed by Co and high-activity PtCo can regulate and control the d-band center of Pt, reduce the adsorption of Pt on oxygen-containing species, and further improve the activity and stability of the catalyst.

Preferably, the nitrogen-containing carbon carrier is a COF, and the COF is in a graphene-like structure.

The nitrogen-containing carbon support may be graphene, carbon nanotubes, conductive carbon black, COF, etc., preferably COF (covalent organic framework) in this application, COF being a class of emerging molecular frameworks linked by covalent bonds, in contrast to conventional carbon support selection. The catalyst has the characteristics of large surface area, high crystallinity, adjustable pore diameter and unique molecular structure, and is gradually explored and applied to the field of electrocatalysts. In the preparation process of the catalyst for the proton exchange membrane fuel cell, the COF can be carbonized into a graphene-like structure, and the heteroatom doping agent can be uniformly distributed in the graphene-like matrix, so that the COF is more suitable for catalyzing a cathode ORR of the fuel cell.

In a second aspect, the present invention also provides a method for preparing a catalyst for a proton exchange membrane fuel cell, which is characterized by comprising the steps of:

s1, uniformly dispersing aminated silicon dioxide spheres and a nitrogen-containing carbon carrier precursor in a solvent, and performing ultrasonic dispersion and degassing, so as to obtain a nitrogen-containing carbon carrier growing on the silicon spheres through solvothermal reaction;

s2, uniformly dispersing the nitrogen-containing carbon carrier, the platinum salt and the transition metal salt growing on the silicon spheres in a solvent, and evaporating the solvent to obtain a composite carrier;

s3, reducing the composite carrier in a reducing atmosphere to obtain a reduction product, and removing silicon spheres and pickling the reduction product to obtain the catalyst for the proton exchange membrane fuel cell.

Firstly, growing a nitrogen-containing carbon carrier on an aminated silicon ball, obtaining a bowl-shaped nitrogen-containing carbon carrier with an optimal configuration through a template removing method in a subsequent step, secondly, introducing Pt salt and transition metal salt, when the nitrogen-containing carbon carrier and the alloy are pyrolyzed together, enabling a reducing atmosphere to pass through pores of the nitrogen-containing carbon carrier and to be pyrolyzed and reduced with Pt-based ions adsorbed on the surface of the carrier, enabling the alloy below the inner part of the pores to be in contact with the reducing atmosphere under the limited-range synthesis effect of the nitrogen-containing carbon carrier with the pores to gradually form a more stable Pt-based core, and enabling the nitrogen-containing oxygen-containing groups on the surface of the nitrogen-containing carbon carrier and the alloy above the pores to react to generate a Pt-based cortex along with complete pyrolysis of the nitrogen-containing carbon carrier and forming a package body with Pt-based alloy particles.

Preferably, the aminated silica spheres are prepared by the steps of:

uniformly dispersing a hydrolysis catalyst and silicon salt in a solvent, and obtaining silicon dioxide balls after stirring, centrifuging and vacuum drying; and uniformly dispersing the silica spheres in a solvent, adding an ammoniation agent for ammoniation reaction, stirring, centrifuging and drying in vacuum to obtain the aminated silica spheres.

Preferably, the ammoniating agent comprises a mixed solution of APTES and ethanol.

Preferably, in the step S1, the nitrogen-containing carbon support precursors are Tp (2, 4, 6-tricarboxyl phloroglucinol) and Pa (p-phenylenediamine), and the nitrogen-containing carbon support grown on the silicon spheres is TpPa-COF.

Preferably, in the step S2, the transition metal salt is a cobalt salt.

Preferably, in the step S2, the mass ratio of the nitrogen-containing carbon carrier, the platinum salt and the transition metal salt grown on the silicon spheres is (140-160): (1.0-5.0): (0.5-1.5), and further preferably is 150:3.0:0.9, so as to achieve the best catalyst performance.

The invention has the beneficial effects that:

1. in the application, the ultra-thin bowl-shaped encapsulation body formed by the nitrogen-containing carbon carrier and the Pt-based intermetallic compound is constructed, so that the ionomer is prevented from poisoning the Pt-based alloy particles, a pore network is constructed, a channel is provided for protons to reach the active sites of the Pt-based particles, and the stability and activity of the catalyst are effectively improved.

2. In the application, the encapsulation body is formed, and simultaneously, a core-shell structure composed of a Pt-based skin layer with high activity and a Pt-based core with high stability is formed, so that the electrochemical activity and stability of the catalyst are further improved.

3. According to the preparation method of the catalyst for the proton exchange membrane fuel cell, provided by the invention, a template removing method is adopted, a nitrogen-containing carbon carrier grows on the surface of the aminated silicon dioxide ball, the silicon ball is etched in the subsequent process, a thin-layer bowl-shaped structure is formed, a carrier model is further optimized, and the mass transfer process of the catalyst in the actual working environment is improved.

Drawings

FIG. 1 is an X-ray diffraction (XRD) curve of the catalyst prepared in each example;

FIG. 2 is a low power transmission electron micrograph of the catalyst prepared in example 1;

FIG. 3 is a high power transmission electron micrograph of the catalyst prepared in example 1;

FIG. 4 is a scanning electron micrograph of the catalyst prepared in example 1;

FIG. 5 is a statistical plot of the particle size distribution of the catalyst prepared in example 1;

FIG. 6 is an X-ray photoelectron spectroscopy (XPS) curve of the catalyst prepared in example 1;

FIG. 7 is a transmission electron micrograph of the catalyst prepared in example 2;

FIG. 8 is a transmission electron micrograph of the catalyst prepared in example 3;

FIG. 9 is a scanning electron micrograph of the catalyst prepared in example 3;

FIG. 10 is a half-wave potential curve of a catalyst prepared in various examples and a commercial Pt/C catalyst in oxygen reduction;

FIG. 11 is a durability curve for the catalyst prepared in example 1 and a commercial Pt/C catalyst;

FIG. 12 is a polarization curve of the catalyst prepared in example 1 under a single cell;

fig. 13 is a polarization curve before and after a durability test under a single cell of the catalyst prepared in example 1.

Detailed Description

The invention is further described below with reference to the drawings and specific examples. Those of ordinary skill in the art will be able to implement the invention based on these descriptions. In addition, the embodiments of the present invention referred to in the following description are typically only some, but not all, embodiments of the present invention. Therefore, all other embodiments, which can be made by one of ordinary skill in the art without undue burden, are intended to be within the scope of the present invention, based on the embodiments of the present invention.

The invention provides a catalyst for a proton exchange membrane fuel cell, which comprises a packaging body formed by a nitrogen-containing carbon carrier and a Pt-based intermetallic compound; the nitrogen-containing carbon carrier is in a bowl-shaped structure and is used for packaging the Pt-based intermetallic compound; the Pt-based intermetallic compound includes Pt and at least one transition metal.

In the above embodiments, the transition metal may be iron, cobalt, nickel, manganese, etc., and is preferably cobalt; the Pt-based intermetallic compound has a core-shell structure composed of a Pt-based skin layer and a Pt-based core, wherein the Pt-based skin layer is PtCo, and the Pt-based core is Pt ₃ Co; the nitrogen-containing carbon carrier can be graphene, carbon nano tube, conductive carbon black, COF and the like, preferably COF, and the COF is in a graphene-like structure; the encapsulation body is nano particles, and the particle size is about 2.85 nm.

In another aspect, the present invention provides a method for preparing a catalyst for a proton exchange membrane fuel cell, comprising the steps of:

In the step S1, the precursors of the nitrogen-containing carbon carriers are preferably Tp and Pa, the prepared nitrogen-containing carbon carriers growing on the silicon spheres are TpPa-COF, the mass ratio of Tp to Pa is (18.5-25.5): (12.5-20.5), preferably 21.66:16.38, the ultrasonic dispersion time is 1-3 min, the stirring time is 2-6 h, and the solvothermal reaction temperature is 110-130 ℃.

In step S2, the transition metal salt may be an iron salt, a cobalt salt, a nickel salt, a manganese salt, or the like, preferably a cobalt salt, more preferably the platinum salt is chloroplatinic acid hexahydrate, the cobalt salt is cobalt chloride hexahydrate, and the mass ratio of the nitrogen-containing carbon carrier grown on the silicon sphere, the platinum salt and the transition metal salt is (140-160): 1.0-5.0): 0.5-1.5, preferably 150:3.0:0.9, the ultrasonic dispersion time is 30-40 min, the stirring time is 3-5 h, the solvent evaporating mode is rotary evaporation, and the rotary evaporation temperature is 50-70 ℃.

In step S3, after the reduction product is obtained, the reduction product is preferably ground, etched into silicon spheres, pickled, and dried to obtain a catalyst for proton exchange membrane fuel cells. The reducing atmosphere is inert gas and hydrogen, preferably argon and hydrogen, the flow ratio of the argon to the hydrogen is (80-90)/(10-20), preferably 90/10, the reaction temperature is 700-900 ℃, and the reaction time is kept at the temperature for more than 2 hours; the condition for etching the silicon ball is that the silicon ball reacts for more than 24 hours at the temperature of 40-60 ℃ in an etchant, wherein the etchant can be hydrofluoric acid, potassium hydroxide, sodium hydroxide and the like, and is preferably potassium hydroxide; the temperature of the drying is 50-60 ℃.

The aminated silica spheres are prepared by the steps of:

Wherein the hydrolysis catalyst is an alkaline solution, preferably ammonia water and ultrapure water; the silicon salt is silicate, preferably tetraethyl silicate; the solvent is an organic solvent, preferably ethanol; the ammoniating agent is preferably an APTES (3-aminopropyl triethoxysilane) solution.

The starting materials used in the examples below were all commercially available conventional chemicals.

Example 1

(1) TpPa-COF growth on aminated silicon spheres:

firstly, 3.4ml of 25% ammonia water, 20ml of ultrapure water and 120ml of ethanol are stirred for 30 minutes, then 12ml of tetraethyl silicate is added, the mixture is fully stirred for 1 hour and centrifuged, ethanol is washed for 3 times, and the mixture is dried in vacuum for 12 hours at 60 ℃ to obtain silica spheres. 1g of silica spheres and 180ml of ethanol are subjected to ultrasonic dispersion and stirring uniformly, 0.3ml of mixed solution of APTES and 20ml of ethanol is added, the mixture is fully stirred for 6 hours and centrifuged, ethanol is washed for 3 times, and the aminated silica spheres are obtained by vacuum drying at 60 ℃.

(2) Preparing a catalyst for a proton exchange membrane fuel cell:

s1, 150mg of aminated silica spheres and 21.66mg of Tp are added into 1.5ml of 1,3, 5-trimethylbenzene and 1.5ml of 1, 4-dioxane solution, the mixture is stirred for 4 hours and uniformly dispersed, 16.38mg of Pa and 0.17 ml acetic acid aqueous solution with the concentration of 3M are added, the ultrasonic dispersion is carried out for 1 minute, after 3 times of liquid nitrogen freezing circulation and degassing, the TpPa-COF carrier growing on the silica spheres is obtained after the solvent thermal reaction at 120 ℃ for 3 days, and the carrier powder is red orange.

S2. 150mg of TpPa-COF carrier grown on silica spheres was dispersed in a mixed solution of 50mL of ultrapure water and 5mL of ethanol and sonicated for 30 minutes, then 3.0mg of Pt (7.4 mg of Pt mL) ^-1 ，H ₂ PtCl ₆ Solution, homemade) and 0.9 mg Co (7.4 mg Co mL) ^-1 ，CoCl ₂ Self-made solution), pouring the solution into the solution, stirring for 12 hours to uniformly disperse the metal source, and obtaining the composite carrier.

S3, rotationally evaporating the composite carrier at 60 ℃ to obtain a precursor in an argon/hydrogen mixed gas (Ar and H) ₂ The gas flow ratio is 90/10), heating to 250 ℃ for two hours at the heating rate of 5 ℃/min, heating to 800 ℃, heat-treating for 2 hours, cooling to room temperature, etching the obtained catalyst powder in 4M KOH for 24 hours, washing by using ultrapure water in a suction filtration mode, washing a filter cake after the suction filtration by using 0.1M perchloric acid for 12 hours, washing by using deionized water in a suction filtration mode, and drying overnight in a drying oven at 55 ℃ to obtain a black powdery catalyst for proton exchange membrane fuel cells, which is named PtCo@NC catalyst.

Referring to FIGS. 1-6, as shown in FIG. 1, the prepared catalyst was found to be crystalline with Pt ₃ Co and PtCo intermetallic compounds are consistent, and the existence of Pt in the form of intermetallic compounds in the catalyst is proved, and two nanoparticle configurations exist simultaneously. As shown in fig. 2 to 5, intermetallic compound rice particles are highly dispersed and concentrated in particle size distribution at 2.85 and nm, and the lattice fringes of catalyst particles can be clearly seen, the carbon layer encapsulation structure of COF carrier can be observed on the nanoparticle surface, andthe COF carrier has a clear bowl-shaped structure. As shown in FIG. 6, it was found that the binding energy of Pt in the prepared catalyst was negatively shifted due to Co alloying, co in the catalyst was in a high valence state, co was electron-transferred to Pt, this alloying effect was beneficial to adjusting the binding energy of Pt with the oxygen intermediate product during the oxygen reduction process, improving the oxygen reduction activity, while the peak intensity fitting of Co profile was poor, mainly due to PtCo and Pt ₃ Under the core-shell structure formed by Co, the signal capture of Co element in the core in the XPS test process is poor, and the prepared catalyst is further proved to have the core-shell structure.

The PtCo@NC catalyst prepared by the steps is subjected to performance test, and the test method comprises the following steps:

cyclic voltammetry test: 50 mu L of Nafion solution which is produced by Aldrich and has the mass fraction of 5% is added into a solution containing 550 mu L of isopropanol and 400 mu L of water, and then 5mg of the catalyst for the proton exchange membrane fuel cell prepared by the steps is added into the solution, and the mixture solution is obtained by ultrasonic dispersion for 30 min; dripping the solution on a glassy carbon electrode to enable the Pt loading capacity on the electrode to be 17 mug Pt cm ^-2 Airing at room temperature to obtain a thin film electrode; a cyclic voltammetry test was performed with a commercial hydrogen standard electrode as reference electrode and a carbon rod as counter electrode in 0.1mol/L perchloric acid saturated with oxygen, at a scan rate of 10 mV/s, see FIG. 10. FIG. 10 is a half-wave potential curve of a catalyst in a perchloric acid solution, wherein the curve Pt/C is the cyclic voltammetry curve of a commercial Pt/C catalyst in a perchloric acid solution (Pt loading on electrode of 20 μg Pt cm) ^-2 ) As can be seen from fig. 10, the half-wave potential of the catalyst prepared in example 1 was 0.92V, which is higher than that of the commercial Pt/C catalyst (0.88V).

Accelerated aging test: the set voltage is 0.6-1.0V, and the result is shown in FIG. 11. FIG. 11 is a graph showing accelerated aging of the catalyst in a perchloric acid solution, and it can be seen from FIG. 11 that the half-wave potential of the catalyst prepared in example 1 does not significantly decrease after 70000 cycles, which is higher than the durability of the commercial Pt/C catalyst (99 mV decrease after 50000 cycles).

Assembled cathode 0.02mg Pt cm ^-2 PtCo@NC single cell with ultra-low load capacityThe performance of the MEA in the actual working process is explored in one step, and the cell polarization test under the working condition of the MEA is carried out: an ink blend was prepared using a catalyst/Nafion (5 wt%) ratio of 70%/30%. The mixtures were sonicated for 1 hour and then sprayed onto one side of a Nafion 211 ionomer membrane with an effective area of about 4cm ² Until the loading reaches 0.02mg Pt cm ^-2 (cathode). Carbon cloth (0.1 mg Pt cm) was deposited at the anode using a commercial Pt/C ^-2 Fuel Cell Etc) as a Gas Diffusion Electrode (GDE). They are then tested in a single cell and condition controlled fuel cell test station (Scribner 850 e). The temperature of both the cell and the gas humidifier was maintained at 80 ℃ throughout the MEA test. Hydrogen H ₂ The back pressure of the Air is kept at 0-2 atm, and the gas flow rates are H respectively ₂ 300 sccm and air 1200-4800 sccm (standard cubic centimeters per minute). The results are shown in FIG. 12, which shows our assembled 0.02mg Pt cm ^-2 PtCo@NC single cell with ultralow cathode loading, and peak power density under hydrogen-air condition of 0.63W cm ^-2 Peak power density under oxyhydrogen conditions was 1.81W cm ^-2 。

Accelerated aging test under MEA operating conditions: the polarization curves before and after the 100k AST cycle, which completely follow the test protocol recommended by DOE guidelines, the potential window is set to the corrosion potential interval of Pt, i.e. 0.6-0.95 v. During the test, H is respectively ₂ Introducing into anode, O ₂ Or air is passed into the cathode. Fig. 13 shows a comparison of polarization curves before and after the aging test, and it can be demonstrated that the power density curves and polarization curves of the oxyhydrogen fuel cell and the hydrogen air fuel cell in the figure show that the ptco@nc catalyst cell shows excellent stability, and the performance of the ptco@nc catalyst cell is almost unchanged in a 100k AST cycle under the hydrogen air condition, almost unchanged in a 30k AST cycle under the oxyhydrogen condition, and slightly attenuated in the 100k AST cycle.

Comparative example 1

The preparation process was essentially the same as in example 1, except that: unlike the TpPa-COF grown on silicon spheres of example 1, which was pyrolyzed together with the alloy, the TpPa-COF grown on silicon spheres of example 2 was subjected to a pyrolysis pretreatment, and the steps after the pretreatment were consistent with the subsequent steps of example 1, and the resulting catalyst for proton exchange membrane fuel cells was designated as ptco@nc-2 catalyst.

Referring to fig. 1 and 7, as shown in fig. 1, the prepared catalyst crystal form and Pt were found ₃ Co and PtCo intermetallic compounds agree, and it is demonstrated that Pt exists as an intermetallic compound in the catalyst. As shown in fig. 7, intermetallic compound nanoparticles were unevenly dispersed, and the carbon layer encapsulation structure of the COF carrier was not observed on the surface thereof, confirming that the COF carrier and the alloy acted to form an encapsulation only when they were pyrolyzed together.

The PtCo@NC-2 catalyst prepared by the above steps was subjected to cyclic voltammetry test, and the test method was the same as in example 1: the half-wave potential of the catalyst was found to be 0.76V, which was a drop relative to example 1, since the pre-pyrolyzed TpPa-COF carrier did not react with the alloy to form an encapsulant, indicating that in example 1, H was found when the COF and PtCo alloys were pyrolyzed ₂ The reducing atmosphere of/Ar passes through the inside of the pores of the COF and is pyrolyzed and reduced with PtCo ions adsorbed on the surface of the carrier, and under the limited-domain synthesis effect of the pores of the COF, the alloy below the inside of the pores is contacted with the reducing atmosphere to gradually form Pt ₃ Co structure. When the COF is gradually pyrolyzed to form a packaging structure, the alloy above the inner part of the pores of the COF is pyrolyzed together with the COF layer, compared with Pt below the inner part of the pores ₃ The Co alloy reacts with the reducing atmosphere, and the nitrogen-containing oxygen-containing groups on the surface of the COF carbon carrier react with the alloy above the pores to generate PtCo alloy.

Comparative example 2

The preparation process was essentially the same as in example 1, except that: unlike example 1, which was followed by subsequent steps of growing TpPa-COF on silicon spheres, example 3, which was directly followed by TpPa-COF growth without addition of aminated silicon spheres, the resulting catalyst for proton exchange membrane fuel cells was designated PtCo@NC-3 catalyst.

Referring to fig. 1, 8 and 9, as can be seen from fig. 1, the prepared catalyst crystal forms were found to be consistent with the Pt3Co and PtCo intermetallic compounds, demonstrating that Pt exists as an intermetallic compound in the catalyst. As shown in fig. 8 and 9, a carbon layer encapsulation structure of the COF carrier in a bowl shape was not observed, and it was confirmed that only the COF grown on the silicon spheres could form an encapsulation with the alloy particles.

The PtCo@NC-3 catalyst prepared by the above steps was subjected to cyclic voltammetry test, and the test method was the same as in example 1: the half-wave potential of the catalyst was found to be 0.73 and V, which is a decrease in half-wave potential relative to example 1, indicating that the structure of the nitrogen-containing carbon carrier and the carrier-encapsulated alloy of the bowl-shaped structure can effectively improve electrochemical activity.

Claims

1. A catalyst for proton exchange membrane fuel cell is characterized in that,

comprises a package body formed by a nitrogen-containing carbon carrier and a Pt-based intermetallic compound; the nitrogen-containing carbon carrier is in a bowl-shaped structure and is used for packaging the Pt-based intermetallic compound; the Pt-based intermetallic compound includes Pt and at least one transition metal.

2. A catalyst for a proton exchange membrane fuel cell as claimed in claim 1, wherein,

the Pt-based intermetallic compound is a core-shell structure consisting of a Pt-based skin layer and a Pt-based core.

3. A catalyst for a proton exchange membrane fuel cell as claimed in claim 2, wherein,

the Pt-based skin layer is PtCo, and the Pt-based core is Pt ₃ Co。

4. A catalyst for a proton exchange membrane fuel cell as claimed in claim 1, wherein,

the nitrogen-containing carbon carrier is a COF, and the COF is of a graphene-like structure.

5. A method for preparing the catalyst for proton exchange membrane fuel cell as claimed in any one of claims 1 to 4, comprising the steps of:

6. The method for preparing a catalyst for proton exchange membrane fuel cell as claimed in claim 5, wherein the aminated silica spheres are prepared by:

7. The method for preparing a catalyst for a proton exchange membrane fuel cell as claimed in claim 6, wherein,

the ammoniating agent comprises a mixed solution of APTES and ethanol.

8. The method for preparing a catalyst for a proton exchange membrane fuel cell as claimed in claim 5, wherein,

in the step S1, the nitrogen-containing carbon carrier precursors are Tp and Pa, and the nitrogen-containing carbon carriers grown on the silicon spheres are TpPa-COF.

9. The method for preparing a catalyst for a proton exchange membrane fuel cell as claimed in claim 5, wherein,

in the step S2, the transition metal salt is a cobalt salt.

10. The method for preparing a catalyst for a proton exchange membrane fuel cell as claimed in claim 5, wherein,

in the step S2, the mass ratio of the nitrogen-containing carbon carrier, the platinum salt and the transition metal salt growing on the silicon spheres is (140-160): 1-5): 0.5-1.5.