CN112993271B

CN112993271B - Catalyst and preparation method thereof

Info

Publication number: CN112993271B
Application number: CN202110190748.2A
Authority: CN
Inventors: 黄玉平; 范书琼; 周有明; 王秀; 米诗阳; 周佳; 张晓华; 吴丹; 朱威
Original assignee: Jiangsu Qingdong New Energy Technology Co ltd
Current assignee: Jiangsu Qingdong New Energy Technology Co ltd
Priority date: 2021-02-19
Filing date: 2021-02-19
Publication date: 2022-05-06
Anticipated expiration: 2041-02-19
Also published as: CN112993271A

Abstract

The application provides a catalyst and a preparation method thereof, belonging to the technical field of fuel cell catalyst preparation. The preparation method of the catalyst comprises the following steps: carrying out high-temperature heat treatment on the catalyst precursor covered with the organic polymer layer to crack and carbonize the organic polymer to form a carbonized layer; wherein the catalyst precursor comprises a carrier and nano metal particles loaded on the carrier. The catalyst precursor having the carbonized layer formed on the surface thereof is subjected to acid treatment in an oxidizing acid solution to remove the carbonized layer. The catalyst has higher activity and longer service life.

Description

Catalyst and preparation method thereof

Technical Field

The application relates to the technical field of fuel cell catalyst preparation, in particular to a catalyst and a preparation method thereof.

Background

Hydrogen energy is used as a secondary energy source, has the advantages of wide source, high mass energy density, environmental friendliness and the like, and is considered as an ideal novel energy source. The hydrogen fuel cell can directly convert chemical energy into electric energy by utilizing hydrogen, has the characteristics of high power density, quick start and the like, and has very outstanding advantages when being applied to the fields of automobiles, fixed power stations, portable power supplies and the like.

At present, the cathode catalyst in the membrane electrode of the fuel cell is mainly platinum-carbon catalyst. The platinum-carbon catalyst is prepared by wet methods such as a liquid phase method, a microwave method and the like.

Disclosure of Invention

The inventor researches and discovers that general platinum-carbon catalysts have the following publication numbers in the patents and literature reports which are published at present: the CN111092235A catalyst prepared by the microwave method has good initial performance, but when the aging performance of the catalyst is tested, the problem that the electrochemical performance of the catalyst is reduced easily in the long-term use process is solved.

The present application aims to provide a catalyst and a preparation method thereof, which can alleviate the above problems and prolong the service life of the catalyst.

In a first aspect, the present application provides a method for preparing a catalyst, comprising the steps of: carrying out high-temperature heat treatment on the catalyst precursor covered with the organic polymer layer to crack and carbonize the organic polymer to form a carbonized layer; wherein the catalyst precursor comprises a carrier and nano metal particles loaded on the carrier. The catalyst precursor having the carbonized layer formed on the surface thereof is subjected to acid treatment in an oxidizing acid solution to remove the carbonized layer.

The catalyst precursor covered with the organic polymer layer is subjected to heat treatment, so that on one hand, the crystallinity of the nano metal particles on the carrier can be improved, the activity of the nano metal particles is improved, and the catalytic effect is better. Alternatively, the organic polymer may be cracked to form a char layer. The carbonization layer is formed through cracking, and the carbonization layer is removed through the oxidizing acid solution (the carbonization layer is removed in the oxidizing acid solution, the oxidizing property of the oxidizing acid solution is reasonable, and when the carbonization layer is removed, the carrier in the catalyst precursor can be prevented from being corroded by the acid solution to a certain extent), the steric hindrance between the metal nano particles can be increased, the aggregation of the metal nano particles in the application process of the catalyst is inhibited, and the service life of the catalyst can be prolonged.

In one possible embodiment, the high temperature heat treatment is carried out at 400-. Optionally, the treatment is carried out for 1-3h at the temperature of 400-650 ℃.

In one possible embodiment, the oxygen-exclusion condition is a reducing atmosphere or an inert atmosphere; optionally, the reducing atmosphere is a hydrogen-argon mixed atmosphere or a hydrogen-nitrogen mixed atmosphere, the volume ratio of the hydrogen to the nitrogen or the argon is 1:100-1:4, and the introduction rate of the mixed gas is 2000-15000 sccm.

In one possible embodiment, the high-temperature heat treatment is carried out in a fixed bed reactor, the material of the fixed bed reactor is quartz glass material, and the fixed bed tube diameter of the fixed bed reactor is 30-50 mm. Can be produced on a large scale by using a fixed bed reactor.

In one possible embodiment, the mass ratio of the nano-metal particles to the support is 2:8 to 7: 3; optionally, the nano-metal particles are platinum nano-particles; the carrier is a solid carbon carrier or a porous carbon carrier with the pore diameter larger than 2 nm.

The carrier is a solid carbon carrier or a porous carbon carrier with the aperture larger than 2nm, and the carbonization layer formed by pyrolysis can be prevented from blocking the pore channel of the carbon carrier to a certain extent, so that the subsequent removal of the carbonization layer can be carried out.

In one possible embodiment, a method for preparing a catalyst precursor covered with a polymer layer comprises: mixing the catalyst precursor with a polymer monomer solution to obtain a mixture, adding an initiator into the mixture to enable the polymer monomer to perform polymerization reaction, taking the solid, and drying to obtain the catalyst precursor covered with the organic polymer layer.

By forming and covering the organic polymer layer on the catalyst precursor during the polymerization reaction, the organic polymer layer can be covered more uniformly and the combination effect of the organic polymer layer and the catalyst precursor is better, so that the service life of the subsequently prepared catalyst is prolonged.

In one possible embodiment, the polymer monomers in the polymer monomer solution include one or more of pyrrole, aniline, and dopamine; the mass of the polymer monomer is 0.3-2.0% of that of the catalyst precursor; the initiator is hydrogen peroxide or/and ammonium persulfate.

In one possible embodiment, the oxidizing acid solution is a nitric acid solution, the molar concentration of the nitric acid solution being less than 2M; optionally, the molar concentration of the nitric acid solution is 0.1-2M.

In one possible embodiment, the time of the acid treatment is 10min to 24 h; the temperature of the acid treatment is 50-80 ℃. The carbonization layer can be effectively removed, and simultaneously, the carrier carbon in the catalyst can be prevented from being reacted.

In a second aspect, the present application provides a catalyst prepared by the above preparation method. The catalyst has higher activity and longer service life.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments are briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive efforts and also belong to the protection scope of the present application.

FIG. 1 is a flow diagram of the preparation of a catalyst provided herein;

FIG. 2 is a transmission electron micrograph of a platinum-carbon catalyst provided in example 1 of the present application;

FIG. 3 is a transmission electron micrograph of a platinum-carbon catalyst provided in example 2 of the present application;

FIG. 4 is a transmission electron micrograph of a platinum carbon catalyst provided in comparative example 1;

FIG. 5 is a transmission electron micrograph of a platinum carbon catalyst provided in comparative example 3;

FIG. 6 is a graph showing the VI performance variation of a monolithic cell during the aging performance test of the catalyst, wherein the membrane electrode prepared by the catalysts provided in examples 1 and 2 of the present application;

FIG. 7 shows the VI performance variation of the monolithic cells of the membrane electrode prepared by the catalysts provided in example 1 and comparative example 1 of the present application during the catalyst aging performance test;

fig. 8 shows the VI performance variation of the membrane electrode prepared by the catalysts provided in example 1 and comparative example 4 of the present application during the catalyst aging performance test of the monolithic cell.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

Fig. 1 is a flow diagram of the preparation of a catalyst provided herein. Referring to fig. 1, the present application provides a method for preparing a catalyst, comprising the following steps:

s10 preparation of catalyst precursor

The catalyst precursor includes a support and nano-metal particles supported on the support. It can be prepared by microwave method with publication number CN 111092235A. It can, of course, also be prepared by other methods, for example: hydrogen high temperature reduction, and the like, and the present application is not limited.

Optionally, the mass ratio of the nano-metal particles to the support is 2:8 to 7:3, illustratively 2:8, 2:7, 2:6, 2:5, 2:4, 2:3, 3:3, 4:3, 5:3, 6:3, or 7: 3.

In the present application, the nano-metal particles are platinum nanoparticles. In other embodiments, the nano-metal particles may also be platinum alloy nanoparticles, iridium and its alloy nanoparticles, ruthenium and its alloy nanoparticles, and the like.

The carrier is a solid carbon carrier or a porous carbon carrier with the pore diameter larger than 2 nm. Illustratively, the carrier is a solid carbon carrier, the carrier is a porous carbon carrier having a pore size of 3 to 10nm, the carrier is a porous carbon carrier having a pore size of 10 to 20nm, the carrier is a porous carbon carrier having a pore size of 20 to 50nm, and the carrier is a porous carbon carrier having a pore size of 50 to 100 nm.

S20, preparing a catalyst precursor covered with an organic polymer layer

Mixing the catalyst precursor and the polymer monomer solution to obtain a mixture, adding an initiator into the mixture, and carrying out polymerization reaction on the polymer monomer to generate an organic polymer layer covered on the catalyst precursor.

In the embodiment of the present application, the polymer monomer in the polymer monomer solution includes one or more of pyrrole, aniline, and dopamine; the solvent in the polymer monomer solution is selected from one of ethanol, Tetrahydrofuran (THF) and deionized water.

Alternatively, the mass of polymer monomer is 0.3% to 2.0% of the mass of catalyst precursor; illustratively, the polymer monomer mass is 0.3%, 0.5%, 1%, 1.5%, or 2.0% of the catalyst precursor mass.

In the embodiment of the application, the initiator is hydrogen peroxide or/and ammonium persulfate. After the initiator is added to the mixture, the initiator promotes polymerization of the polymer monomers to give an organic polymer which is coated on the catalyst precursor by means of a layer structure.

In the present application, the polymer monomer may be dissolved in a solvent to obtain a polymer monomer solution. The catalyst precursor was dispersed in ethanol under nitrogen protection to obtain a catalyst precursor dispersion. And continuously under the protection of nitrogen, uniformly mixing the polymer monomer solution and the catalyst precursor dispersion liquid, and stirring for 0.5-3h at the temperature of 2-5 ℃ to obtain a first suspension (mixture). Dissolving an initiator in deionized water to obtain an initiator solution, adding the initiator solution into the first suspension, continuously stirring for 10-24h at the temperature of 2-5 ℃, polymerizing a polymer monomer, filtering by using a vacuum filtering device, washing by using ethanol and deionized water until the conductivity is less than or equal to 10 mu S/cm, and drying for 10-24h at the temperature of 35-45 ℃ in a vacuum drying device to obtain the catalyst precursor covered with the organic polymer layer.

In other embodiments, the organic polymer solution and the catalyst precursor solution may also be mixed such that the surface of the catalyst precursor is covered with the organic polymer layer.

And S30, carrying out high-temperature heat treatment on the catalyst precursor covered with the organic polymer layer to crack and carbonize the organic polymer to form a carbonized layer. The catalyst precursor covered with the organic polymer layer is subjected to heat treatment, so that on one hand, the crystallinity of the nano metal particles on the carrier can be improved, the activity of the nano metal particles is improved, and the catalytic effect is better. Alternatively, the organic polymer may be cracked to form a char layer.

Alternatively, the high temperature heat treatment is carried out for 0.5-3h under the anaerobic condition with the temperature of 400-800 ℃. The organic polymer can be more easily cracked to form a carbonized layer by processing under anaerobic condition, and the organic polymer can not generate aerobic reaction. Further, the treatment is carried out for 1-3h at the temperature of 400-650 ℃.

Illustratively, the temperature of the high temperature heat treatment is 400 ℃, 500 ℃, 600 ℃, 700 ℃ or 800 ℃; the time of the high-temperature heat treatment is 0.5h, 1h, 1.5h, 2h, 2.5h or 3 h.

In the present application, the oxygen-exclusion condition is a reducing atmosphere or an inert atmosphere; optionally, the reducing atmosphere is a hydrogen-argon mixed atmosphere or a hydrogen-nitrogen mixed atmosphere, the volume ratio of the hydrogen to the nitrogen or the argon is 1:100-1:4, and the introduction rate of the mixed gas is 2000-15000 sccm.

For example: the reducing atmosphere is a mixed atmosphere of hydrogen and argon, the volume ratio of the hydrogen to the argon is 1:100-1:4, and the introduction rate of the mixed gas of the hydrogen and the argon is 2000-15000 sccm. Illustratively, the volume ratio of hydrogen to argon is 1:100, 1:80, 1:50, 1:20, 1:10, or 1: 4; the mixed gas is introduced at a rate of 2000sccm, 5000sccm, 8000sccm, 10000sccm, 12000sccm, or 15000 sccm.

For example: the reducing atmosphere is a mixed atmosphere of hydrogen and nitrogen, the volume ratio of the hydrogen to the nitrogen is 1:100-1:4, and the introduction rate of the mixed gas of the hydrogen and the nitrogen is 2000-15000 sccm. Illustratively, the volume ratio of hydrogen to nitrogen is 1:100, 1:80, 1:50, 1:20, 1:10, or 1: 4; the mixed gas is introduced at a rate of 2000sccm, 5000sccm, 8000sccm, 10000sccm, 12000sccm, or 15000 sccm.

In other embodiments, the inert atmosphere may be a nitrogen atmosphere, an argon atmosphere, or the like.

In the application, high-temperature heat treatment is carried out in a fixed bed reactor, the fixed bed reactor is provided with an air inlet and an air outlet, a catalyst precursor covered with an organic polymer layer is placed in the fixed bed reactor, then the inert gas or the mixed gas is introduced into the fixed bed reactor, oxygen in the reactor is replaced, then the fixed bed reactor is heated, the temperature of the fixed bed reactor is reached to heat treatment, and the heat is preserved for a period of time, so that the organic polymer layer is cracked to form a carbonization layer.

Optionally, the fixed bed reactor is made of quartz glass, and the fixed bed pipe diameter of the fixed bed reactor is 30-50 mm. The fixed bed tube diameter of the fixed bed reactor is, by way of example, 30mm, 35mm, 40mm, 45mm or 50 mm.

And S40, placing the catalyst precursor with the carbonization layer formed on the surface in an oxidizing acid solution for acid treatment to remove the carbonization layer. In the process of cracking to form a carbonized layer and removing the carbonized layer, the steric hindrance among the metal nano particles can be increased, the aggregation of the metal nano particles in the application process of the catalyst is inhibited, and the service life of the catalyst can be prolonged. And the carbonized layer is removed in the oxidizing acid solution, the oxidizing property of the oxidizing acid solution is reasonable, and the carrier in the catalyst precursor can be prevented from being corroded by the acid solution to a certain extent while the carbonized layer is removed.

Optionally, the oxidizing acid solution is a nitric acid solution, and the molar concentration of the nitric acid solution is less than 2M; alternatively, the molar concentration of the nitric acid solution is 0.1-2M. The acid treatment time is 10min-24 h; the temperature of the acid treatment is 50-80 ℃. Illustratively, the molar concentration of the nitric acid solution is 0.1M, 0.5M, 1M, 1.5M, or 1.95M; the acid treatment time is 10min, 30min, 1h, 3h, 5h, 10h, 15h or 24 h; the temperature of the acid treatment is 50 ℃, 60 ℃, 70 ℃ or 80 ℃.

The catalyst prepared by the method has higher activity and longer service life.

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

A preparation method of the catalyst comprises the following steps:

(1) and dispersing the carbon carrier in ethylene glycol, adding chloroplatinic acid, ultrasonically dispersing for 120min, and mechanically rotating and stirring to obtain a first suspension. And mechanically stirring the first suspension at room temperature, and adjusting the pH value to 11 by using sodium hydroxide to obtain a second suspension. And (3) radiating the second suspension for 500s under 2000w of microwave, washing with deionized water, and drying in vacuum at 80 ℃ to obtain the platinum-carbon catalyst. The platinum-carbon catalyst had a platinum to carbon mass ratio of 1: 1.

(2) And dissolving 0.02g of pyrrole monomer in 100mL of ethanol, and uniformly stirring to obtain a pyrrole monomer solution. 2g of platinum-carbon catalyst was dispersed in 200mL of ethanol under nitrogen protection to obtain a platinum-carbon catalyst dispersion. Under the protection of nitrogen, pyrrole monomer solution and platinum-carbon catalyst dispersion liquid are uniformly mixed, and stirred for 1h at 4 ℃ to obtain first suspension.

(3) 100mg of ammonium persulfate as an initiator was dissolved in 50g of deionized water to obtain an initiator solution. Adding 3mL of initiator solution into the first suspension, and stirring at 4 ℃ for 12h, wherein pyrrole monomers are polymerized into polypyrrole in the process. After polymerization, filtering by using a vacuum filtering device, washing by using ethanol and deionized water until the conductivity is less than or equal to 10 mu S/cm, and drying at 40 ℃ for 12h under-0.08 MPa to obtain the platinum-carbon catalyst covered with the organic polymer.

(4) Transferring the platinum-carbon catalyst covered with the polymer to a tubular furnace, introducing high-purity nitrogen for 20min, and introducing H at the rate of 20sccm₂While introducing N at a rate of 500sccm₂Raising the temperature to 500 ℃ at the rate of 5 ℃/min, preserving the temperature for 1h, introducing nitrogen to protect and cool the temperature to room temperature, and taking out a sample to obtain the platinum-carbon catalyst with the carbonized layer.

(5) Stirring and acid-treating the platinum-carbon catalyst powder with the carbonized layer in 1M nitric acid solution at 60 ℃ for 4h to oxidize and etch the carbon layer on the surface, then carrying out vacuum filtration, washing the carbon layer to be neutral by deionized water, and then drying the carbon layer at 40 ℃ for 12h in vacuum to obtain the platinum-carbon catalyst.

Example 2

A preparation method of the catalyst comprises the following steps:

(2) And dissolving 1g of pyrrole monomer in 4.8L of ethanol, and uniformly stirring to obtain a pyrrole monomer solution. 100g of the platinum-carbon catalyst was dispersed in 9L of ethanol under a nitrogen atmosphere to obtain a platinum-carbon catalyst dispersion liquid. Under the protection of nitrogen, pyrrole monomer solution and platinum-carbon catalyst dispersion liquid are uniformly mixed, and stirred for 12 hours at 4 ℃ to obtain first suspension.

(3) 400mg of ammonium persulfate as an initiator was dissolved in 200g of deionized water to obtain an initiator solution. 150mL of initiator solution is added into the first suspension, and the mixture is stirred for 24h at 4 ℃, and pyrrole monomers are polymerized into polypyrrole in the process. After polymerization, filtering by using a vacuum filtering device, washing by using ethanol and deionized water until the conductivity is less than or equal to 10 mu S/cm, and drying for 24h at 40 ℃ under-0.08 MPa to obtain the platinum-carbon catalyst covered with the organic polymer.

(4) Transferring the platinum-carbon catalyst covered with the polymer into a fixed bed reactor, introducing high-purity nitrogen for 20min, and introducing H at the rate of 300sccm₂While introducing N at a rate of 12000sccm₂Raising the temperature to 500 ℃ at the rate of 5 ℃/min, preserving the temperature for 1h, introducing nitrogen to protect and cool the temperature to room temperature, and taking out a sample to obtain the platinum-carbon catalyst with the carbonized layer.

(5) Stirring the platinum-carbon catalyst powder with the carbonized layer in 1.5M nitric acid solution at 60 ℃ for acid treatment for 6h to oxidize and etch the carbon layer on the surface, then carrying out vacuum filtration, washing the carbon layer to be neutral by deionized water, and then drying the carbon layer at 40 ℃ in vacuum for 24h to obtain the platinum-carbon catalyst.

Comparative example 1

Comparative example 1 is an improvement made on the basis of example 1, and the catalyst of comparative example 1 is a platinum-carbon catalyst obtained in step (1) in example 1.

Comparative example 2

Comparative example 2 is an improvement over example 1, and the catalyst of comparative example 2 is a platinum-carbon catalyst with a carbonized layer obtained in example 1 without performing step (5).

Comparative example 3

Comparative example 3 is an improvement over example 1, and the preparation method of the catalyst of comparative example 3 comprises the following steps:

(2) Transferring the platinum-carbon catalyst to a tubular furnace, introducing high-purity nitrogen for 20min, and introducing H at the rate of 20sccm₂While introducing N at a rate of 500sccm₂Raising the temperature to 500 ℃ at the rate of 5 ℃/min, preserving the temperature for 1h, introducing nitrogen to protect and cool the temperature to room temperature, and taking out a sample to obtain the platinum-carbon catalyst after heat treatment.

Comparative example 4

Comparative example 4 is an improvement over example 1, and comparative example 4 is different from example 1 in that in step (5) of comparative example 4, the platinum-carbon catalyst powder having a carbonized layer is subjected to stirring acid treatment in a 2M nitric acid solution at 60 ℃ for 8 hours.

Examples of the experiments

The catalysts obtained in example 1, example 2 and comparative example 1 to comparative example 4 are applied to a membrane electrode, and the preparation method of the membrane electrode is as follows:

0.5g of the catalyst powder was added to nafion membrane solution containing 0.25g of ionomer and a mixed solution of 40g of ethanol and water (V ethanol: V water: 4:1), dispersed in an ice-water bath at 8000rpm for 1 hour using a high-speed shear emulsifier, and then sprayed on the cathode side of the proton membrane at 0.40mg/cm using an ultrasonic atomizing sprayer²Pt, 0.025mg/cm sprayed on the anode side²And Pt, and packaging to obtain a membrane electrode sample.

Hydrogen (0.5L/min) was distributed to the anodes and air (1L/min) was distributed to the cathodes, with anode relative humidity set to 25%, cathode humidity set to 50%, anode stack pressure 80kpa, cathode stack pressure 70kpa, stack temperature 75 ℃. And (3) loading to the maximum current, activating for about 30min under the condition of hydrogen and oxygen with constant current, then switching the cathode into air, and finally testing the initial performance of the membrane electrode VI after the voltage is stable for about 15 min.

Hydrogen (0.2L/min) was dispensed into the anode and nitrogen (0.075L/min) into the cathode, setting the cathode-anode relative humidity to 100%, the cathode-anode stack pressure to atmospheric, and the stack temperature to 80 ℃. A 0.6V 3s, 0.95V 3s square wave cycle was performed. And (5) carrying out a catalyst aging test.

In the examples and comparative examples, the raw material and electrochemical performance parameters are shown in table 1, and the distribution of platinum particles on the finally obtained catalyst is shown in the transmission electron microscope images of the platinum-carbon catalyst provided in fig. 2 to 5. Electrochemical performance evaluation VI results of the membrane electrode monolithic cells are shown in fig. 6-8.

TABLE 1 preparation conditions of the catalyst and electrochemical Properties of the Membrane electrode

Referring to fig. 2 to 8 together with table 1, it can be seen from fig. 2 (transmission electron microscope images of the platinum-carbon catalyst provided in example 1) and fig. 3 (transmission electron microscope images of the platinum-carbon catalyst provided in example 2) that the platinum particle size distribution of the obtained catalyst is not greatly different regardless of whether the high-temperature heat treatment is carried out in the tubular furnace (example 1) or the fixed bed reactor (example 2). As can be seen from fig. 6 (VI performance variation graph of monolithic cell in catalyst aging performance test process of membrane electrode prepared by catalysts provided in examples 1 and 2), the electrochemical performance effect of the catalyst applied on membrane electrode is equivalent, and large-scale production can be performed by using fixed bed reactor.

As can be seen from fig. 2 (tem image of the platinum-carbon catalyst provided in example 1), fig. 4 (tem image of the platinum-carbon catalyst provided in comparative example 1) and fig. 7 (VI performance change of the membrane electrode prepared from the catalysts provided in example 1 and comparative example 1 during the catalyst aging performance test process of the monolithic cell), after the high-temperature heat treatment, the platinum particles on the catalyst still maintain a good state, which not only improves the electrochemical initial performance of the catalyst on the membrane electrode, but also has better performance after the catalyst aging performance test is finished.

As can be seen from comparison of example 1 with comparative example 3 in table 1, and from comparison of fig. 2 (transmission electron micrograph of platinum carbon catalyst provided in example 1) with fig. 5 (transmission electron micrograph of platinum carbon catalyst provided in comparative example 3), if organic polymer is not coated, agglomeration of platinum particles on the catalyst during heat treatment becomes large easily, and the half-cell electrochemical active area (ECSA) decreases.

As can be seen from comparison of example 1 and comparative example 2 in table 1, if the carbonized layer is not removed by using the oxidizing acid after the heat treatment, the electrochemical active area (ECSA) of the half cell is reduced, and the electrochemical active area of the catalyst is small, which indirectly indicates that the organic coating effect is good, and the platinum particles on the catalyst are effectively coated.

As can be seen from comparison of example 1 with comparative example 4 in table 1, and as can be seen from fig. 8 (VI performance change of the membrane electrode prepared from the catalysts provided in example 1 and comparative example 4 during the catalyst aging performance test of a single cell), the organic-coated carrier is removed by the high-concentration nitric acid oxidation treatment, so that the half-cell electrochemical active area (ECSA) thereof is increased, but the performance after the catalyst aging is significantly reduced in the membrane electrode test.

The embodiments described above are some, but not all embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Claims

1. A preparation method of a catalyst is characterized by comprising the following steps:

mixing a catalyst precursor with a polymer monomer solution to obtain a mixture, adding an initiator into the mixture to enable the polymer monomer to perform polymerization reaction, taking a solid, and drying to obtain the catalyst precursor covered with an organic polymer layer;

carrying out high-temperature heat treatment on the catalyst precursor covered with the organic polymer layer to crack and carbonize the organic polymer to form a carbonized layer; wherein the catalyst precursor comprises a support and nano-metal particles supported on the support;

and placing the catalyst precursor with the carbonization layer formed on the surface in an oxidizing acid solution for acid treatment so as to remove the carbonization layer.

2. The method as claimed in claim 1, wherein the high temperature heat treatment is carried out at 400-800 ℃ under anaerobic conditions for 0.5-3 h.

3. The method as claimed in claim 2, wherein the treatment is carried out at a temperature of 400-650 ℃ for 1-3 h.

4. The method of claim 2, wherein the anaerobic condition is a reducing atmosphere or an inert atmosphere.

5. The method according to claim 4, wherein the reducing atmosphere is a mixed hydrogen-argon atmosphere or a mixed hydrogen-nitrogen atmosphere, the volume ratio of hydrogen to nitrogen or argon is 1:100-1:4, and the introduction rate of the mixed gas is 2000-15000 sccm.

6. The preparation method according to any one of claims 1 to 5, wherein the high-temperature heat treatment is carried out in a fixed bed reactor, the material of the fixed bed reactor is quartz glass, and the fixed bed diameter of the fixed bed reactor is 30-50 mm.

7. The production method according to claim 1, wherein the mass ratio of the nano-metal particles to the support is 2:8 to 7: 3.

8. The production method according to claim 7, wherein the nano-metal particles are platinum nanoparticles; the carrier is a solid carbon carrier or a porous carbon carrier with the pore diameter larger than 2 nm.

9. The method according to claim 1, wherein the polymer monomer in the polymer monomer solution comprises one or more of pyrrole, aniline, and dopamine; the mass of the polymer monomer is 0.3-2.0% of that of the catalyst precursor;

the initiator is hydrogen peroxide or/and ammonium persulfate.

10. The production method according to any one of claims 7 to 9, wherein the oxidizing acid solution is a nitric acid solution having a molar concentration of less than 2M.

11. The method of claim 10, wherein the nitric acid solution has a molar concentration of 0.1 to 2M.

12. The production method according to any one of claims 7 to 9, wherein the acid treatment time is 10min to 24 hours; the temperature of the acid treatment is 50-80 ℃.

13. A catalyst prepared by the method of any one of claims 1 to 12.