Fuel cell cathode catalyst and preparation method thereof, and method for improving sulfur poisoning resistance of proton exchange membrane fuel cell cathode

Abstract

The invention relates to the technical field of fuel cell cathode catalyst preparation, and discloses a fuel cell cathode catalyst and a preparation method thereof, and a method for improving the sulfur poisoning resistance of a proton exchange membrane fuel cell cathode, and the preparation method comprises the following steps: (1) under a stirring condition, mixing tetraammineplatinum acetate, transition metal acetate, citric acid and a solvent, and stirring to obtain a mixed solution; carrying out coordination reaction, and carrying out solid-liquid separation to obtain a product solution; (2) removing a solvent in the product solution, and then drying to obtain a precursor material; (3) performing high-temperature pyrolysis on the precursor material in an inert atmosphere; (4) contacting the high-temperature pyrolysis product with acid, and then optionally washing and drying; and (5) mixing the product obtained in the step (4) with conductive carbon black. The material shows good sulfur poisoning resistance when being applied to a cathode catalytic oxygen reduction reaction of a proton exchange membrane fuel cell.

Description

Fuel cell cathode catalysts and their preparation methods; methods to improve the sulfur poisoning resistance of proton exchange membrane fuel cell cathodes. Technical Field

[0001] This invention relates to the field of fuel cell cathode catalyst preparation technology, specifically to a fuel cell cathode catalyst and its preparation method, and a method for improving the sulfur poisoning resistance of proton exchange membrane fuel cell cathodes. Background Technology

[0002] Hydrogen energy is a clean and efficient energy source that can be quickly converted into electricity and heat, making it an ideal alternative to fossil fuels. Proton exchange membrane fuel cells (PEMFCs) convert the chemical energy of hydrogen into electrical energy through an electrochemical reaction, offering advantages such as rapid start-up and high energy conversion efficiency. In a PEMFC, a hydroxide reaction occurs at the anode, and an oxygen reduction reaction occurs at the cathode. Compared to the hydroxide reaction, the oxygen reduction reaction involves the gain and loss of many electrons and has a slower rate. Currently, noble metal Pt / C catalysts are commonly used to accelerate the oxygen reduction reaction. However, the Pt-catalyzed oxygen reduction reaction requires high oxygen purity; even trace amounts of sulfur-containing substances such as SO2 in the air can poison the catalyst, thus affecting fuel cell performance. Furthermore, the ionomer Nafion contains sulfonic acid groups, which, upon direct contact with the catalyst, can also cause deactivation of active sites. The cathode catalyst is a crucial factor affecting fuel cell performance; therefore, improving the cathode catalyst's resistance to sulfur poisoning is of great significance for improving fuel cell performance and lifespan. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of poor sulfur poisoning resistance of existing fuel cell cathode catalysts, and to provide a fuel cell cathode catalyst and its preparation method, as well as a method for improving the sulfur poisoning resistance of proton exchange membrane fuel cell cathodes. This fuel cell cathode catalyst has good sulfur poisoning resistance.

[0004] To achieve the above objectives, the present invention provides a method for preparing a fuel cell cathode catalyst, the method comprising:

[0005] (1) Under stirring conditions, tetraammineplatinum acetate, transition metal acetate, citric acid and solvent are mixed to carry out a coordination reaction. After solid-liquid separation, the product solution is obtained.

[0006] The transition metal is selected from at least one of Ni, Co, and Zn;

[0007] (2) Remove the solvent from the product solution and then dry it to obtain the precursor material;

[0008] (3) The precursor material is subjected to high-temperature pyrolysis under an inert atmosphere;

[0009] (4) The products of high-temperature pyrolysis are brought into contact with acid, and then optionally washed and dried;

[0010] (5) Mix the product from step (4) with conductive carbon black.

[0011] Preferably, the total concentration of platinum and transition metals in the product solution is 0.01-0.15 mol / L, more preferably 0.07-0.12 mol / L; and the concentration of citric acid is 0.01-0.2 mol / L, more preferably 0.02-0.15 mol / L.

[0012] A second aspect of the present invention provides a fuel cell cathode catalyst prepared by the above-described preparation method.

[0013] A third aspect of the present invention provides a method for improving the sulfur poisoning resistance of a proton exchange membrane fuel cell cathode, the method comprising: using the fuel cell cathode catalyst described in the second aspect.

[0014] This invention creatively utilizes the residual mother liquor from the coordination reaction of tetraammineplatinum acetate, transition metals, and citric acid as a raw material for preparing carbon-coated platinum alloy nanomaterials. Carbon-coated platinum-transition metal alloy nanomaterials can be prepared through a one-step pyrolysis of the precursor. This material exhibits excellent resistance to sulfur poisoning when applied to the catalytic oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell.

[0015] In addition, the preparation method provided by the present invention can make full use of the remaining products of the coordination reaction, improve the utilization rate of raw materials, and reduce the discharge of waste liquid. Attached Figure Description

[0016] Figure 1 is the XRD pattern of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0017] Figure 2 is a TEM image of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0018] Figure 3 is the XPS full spectrum of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0019] Figure 4 is the LSV curve of the carbon-coated platinum-nickel alloy nanomaterial prepared in Example 1 before and after poisoning by catalytic oxygen reduction reaction.

[0020] Figure 5 is the LSV curve of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 2 before and after poisoning by catalytic oxygen reduction reaction.

[0021] Figure 6 shows the LSV curves of Comparative Example 1 before and after poisoning in the catalytic oxygen reduction reaction. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] The first aspect of this invention provides a method for preparing a fuel cell cathode catalyst, the method comprising:

[0024] (1) Under stirring conditions, tetraammineplatinum acetate, transition metal acetate, citric acid and solvent are mixed to carry out a coordination reaction. After solid-liquid separation, the product solution is obtained.

[0025] The transition metal is selected from at least one of Ni, Co, and Zn;

[0026] (2) Remove the solvent from the product solution and then dry it to obtain the precursor material;

[0027] (3) The precursor material is subjected to high-temperature pyrolysis under an inert atmosphere;

[0028] (4) The products of high-temperature pyrolysis are brought into contact with acid, and then optionally washed and dried;

[0029] (5) Mix the product from step (4) with conductive carbon black.

[0030] The inventors of this invention discovered that tetraammineplatinum acetate, transition metal acetate, and citric acid can promote a coordination reaction between tetraammineplatinum, the transition metal, and citric acid. The remaining mother liquor from this coordination reaction is used as a raw material for preparing carbon-coated platinum alloy nanomaterials. Carbon-coated platinum-transition metal alloy nanomaterials can be prepared through a one-step pyrolysis of the precursor. This material exhibits excellent resistance to sulfur poisoning when applied to the catalytic oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell.

[0031] According to the present invention, the transition metal is selected from at least one of Ni, Co and Zn, more preferably Ni.

[0032] According to some preferred embodiments of the present invention, the use of Pt and Ni in combination can further improve the catalyst's resistance to sulfur poisoning.

[0033] According to some preferred embodiments of the present invention, the molar ratio of tetraammineplatinum acetate (calculated as platinum) to transition metal acetate (calculated as a transition metal element) is 1:(1-10), for example, it can be a specific molar ratio or any range between the two, such as 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, etc. Preferably, the molar ratio of tetraammineplatinum acetate (calculated as platinum) to transition metal acetate (calculated as a transition metal element) is 1:(3-7).

[0034] In this invention, tetraammineplatinum acetate, transition metal acetate, and citric acid are all commercially available. The transition metal acetate and / or citric acid may also contain water of crystallization, as is well known to those skilled in the art.

[0035] According to some preferred embodiments of the present invention, the total molar amount of tetraammineplatinum acetate and transition metal acetate, calculated as metal elements, to citric acid is in a molar ratio of 1:(0.1-5), preferably 1:(0.3-2).

[0036] According to the present invention, the coordination reaction is carried out in the presence of a solvent. The present invention does not particularly limit the type of solvent, but the solvent should be capable of sufficiently dissolving and dispersing tetraammineplatinum acetate, transition metal acetate, and citric acid. Preferably, the solvent is water. The present invention also does not particularly limit the amount of solvent used, but the amount should also be capable of sufficiently dissolving and dispersing the reactants. Those skilled in the art can select the appropriate amount based on actual needs.

[0037] According to some preferred embodiments of the present invention, the total concentration of platinum and transition metals in the product solution is 0.01-0.15 mol / L, and the concentration of citric acid is 0.01-0.2 mol / L. Preferably, the total concentration of platinum and transition metals is 0.07-0.12 mol / L, and the concentration of citric acid is 0.02-0.15 mol / L. Controlling the concentrations of metals and citric acid in the product solution within the above ranges is beneficial for preparing carbon-coated platinum-nickel alloy nanomaterials with a suitable number of carbon shell layers, and is beneficial for further improving the catalytic activity and anti-poisoning ability of the prepared catalyst.

[0038] This invention does not impose particular limitations on the stirring rate or the specific conditions of the coordination reaction, as long as the three components can react sufficiently. Preferably, the conditions for the coordination reaction include: a temperature of 40-100℃, more preferably 60-80℃, and a time of 3-16 hours, more preferably 6-12 hours. Adopting the above-mentioned preferred embodiments is beneficial for further improving the activity and stability of the oxygen reduction reaction of the obtained material.

[0039] In this invention, the products of the coordination reaction include a coordination compound precipitate and a product solution. The precipitate can be separated from the products of the coordination reaction by any solid-liquid separation method to obtain the product solution. For example, filtration, vacuum filtration, centrifugation, etc. can be used. Those skilled in the art can choose according to their needs.

[0040] In this invention, the solvent in the product solution can be removed using any conventional method in the art to obtain the solute. Preferably, evaporation can be used.

[0041] The present invention does not particularly limit the drying method and conditions, and can adopt conventional methods in the art. Preferably, the drying is vacuum drying, the drying temperature is 50-100℃, and the drying time is 6-14h.

[0042] According to the present invention, the pyrolysis process described in step (3) can promote the alloying of platinum with transition metals to form carbon-coated platinum-transition metal alloy nanomaterials. The above preparation method can improve the utilization rate of platinum. The catalytic activity of carbon-coated platinum-based alloy nanomaterials in electrocatalytic oxygen reduction reaction can be improved through induction effect and strain effect. In addition, the presence of carbon shell can inhibit the dissolution of metal elements and the agglomeration of alloy nanoparticles, thereby improving stability.

[0043] In this invention, in step (3), the inert gas refers to any non-reactive gas that does not participate in the reaction. Preferably, the inert gas is nitrogen and / or argon.

[0044] Preferably, the flow rate of the inert gas is 20-120 mL / min, and more preferably 60-100 mL / min.

[0045] According to some preferred embodiments of the present invention, the pyrolysis temperature is 400-1000℃, for example, it can be a specific but not limiting pyrolysis temperature such as 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, or any range between the two. Preferably, the pyrolysis temperature is 500-700℃.

[0046] In this invention, the high-temperature pyrolysis is performed by heating to the above-mentioned pyrolysis temperature through a program, and then maintaining the temperature. Preferably, the heating rate of the high-temperature pyrolysis is 2-10℃ / min, and more preferably 2-8℃ / min.

[0047] Preferably, the isothermal time for the high-temperature pyrolysis is 1-6 hours, and more preferably 2-5 hours.

[0048] After the above-mentioned high-temperature pyrolysis, it is preferable to allow the pyrolysis products to cool naturally in an inert atmosphere, then grind them appropriately before proceeding with subsequent acid contact.

[0049] According to the present invention, in step (4), the purpose of contacting the product of high-temperature pyrolysis with acid is to remove the uncoated metal in the pyrolysis product. The acid can be an acid commonly used in the art, as long as it can properly remove the uncoated metal in the pyrolysis product. Preferably, the acid can be an inorganic acid and / or an organic acid, and more preferably at least one of sulfuric acid, nitric acid and hydrochloric acid.

[0050] Preferably, the amount of acid used is 40-100 mL, more preferably 40-80 mL, relative to 1 g of high-temperature pyrolysis product.

[0051] According to some preferred embodiments of the present invention, in step (4), the acid is provided by an aqueous solution of an acid. Preferably, the acid is provided by a sulfuric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C; or, the acid is provided by a nitric acid solution with a concentration of 0.5-15 mol / L and a contact temperature of 25-60°C; or, the acid is provided by a hydrochloric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C.

[0052] Preferably, in step (4), the contact time is 3-50 hours, more preferably 3-24 hours.

[0053] According to the present invention, in step (4), the purpose of washing is to remove the acid remaining on the pyrolysis products during the pickling process. Therefore, various water washing methods that can wash the pyrolysis products to neutral pH are applicable to the present invention. Preferably, washing is performed until the pH of the washing solution is neutral.

[0054] According to the present invention, the purpose of drying in step (4) is to remove water from the pickling product. Therefore, drying can be carried out under normal pressure or reduced pressure, preferably under vacuum, at a temperature of 60-80°C for 4-12 hours.

[0055] According to the present invention, the product obtained in step (4) is a carbon-coated platinum-based alloy nanomaterial, which contains a platinum-transition metal alloy particle core and a graphitized carbon layer coated on the surface of the platinum-transition metal alloy particle core.

[0056] Preferably, when the transition metal is Ni, the XRD pattern of the carbon-coated platinum-based alloy nanomaterial exhibits two characteristic diffraction peaks at 2θ between 39.7° and 44.7°, and no characteristic diffraction peaks for Pt and / or Ni are present. The diffraction peak at the lower angle corresponds to a platinum-rich alloy phase, while the diffraction peak at the higher angle corresponds to a nickel-rich alloy phase.

[0057] In this invention, there are no particular limitations on the conductive carbon black, which can be obtained commercially, such as Ketjen black (e.g., ECT-600JD) or Cabot carbon black (e.g., Vulcan XC 72).

[0058] According to some preferred embodiments of the present invention, the weight ratio of the product obtained in step (4) to the conductive carbon black is 1:0.1-5, preferably 1:0.1-1.

[0059] A second aspect of the present invention provides a fuel cell cathode catalyst prepared by the above-described preparation method.

[0060] A third aspect of the present invention provides a method for improving the sulfur poisoning resistance of a proton exchange membrane fuel cell cathode, the method comprising: using the membrane fuel cell cathode catalyst described in the second aspect.

[0061] The present invention will be described in detail below through embodiments.

[0062] The surface morphology of the material was characterized by high-resolution transmission electron microscopy (HRTEM, JEM-2100, NEC Corporation) and scanning electron microscopy (SEM, model: S-4800, Hitachi). The accelerating voltage of HRTEM was 200 kV and the accelerating voltage of SEM was 5 kV.

[0063] The crystal structure of the material was characterized by X-ray diffraction (XRD, Malvern Panaco GmbH, Netherlands, Empyrean). The test conditions were: Cu target, Kα rays, tube voltage 40 kV, tube current 40 mA, and scan rate 2° / min.

[0064] The carbon, hydrogen, and oxygen content was measured using an Elementar Vario EL Cube elemental analyzer. The specific procedure was as follows: Approximately 5 mg of sample was weighed into a tin cup, placed in the autosampler tray, and introduced into the combustion tube via a ball valve. Combustion was performed at 1000℃ (helium purging was used to eliminate atmospheric interference during injection). The carbon and hydrogen in the sample were converted into carbon dioxide and water, respectively. The mixed gas was separated by a chromatographic column and finally detected by a thermal conductivity cell. For oxygen determination, the sample was pyrolyzed in a high-temperature pyrolysis tube containing carbon powder. The oxygen in the sample was converted into carbon monoxide. The carrier gas carried the pyrolysis products into a series of scrubbers to remove acid gases and water vapor, and finally detected by an infrared detector.

[0065] The content of platinum and transition metal elements was determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The specific method is as follows: (1) Nitration: 10 mg of catalyst sample was placed in a flask, 16 mL of freshly prepared aqua regia was added, a magnetic stir bar was added, the flask was placed in an oil bath, refluxed at 120 °C for 12 h, and after cooling to room temperature, the solution was drawn up with a glass syringe and filtered with a disposable filter with a pore size of 0.22 μm. The filtrate was added to a 500 mL volumetric flask and diluted with ultrapure water. (2) Content test: 10 mL of the solution after nitration and dilution was taken and the metal content was tested using an Agilent 5110 instrument.

[0066] Example 1

[0067] (1) 2.0 g of tetraammineplatinum acetate, 7.6 g of nickel acetate tetrahydrate, and 8.7 g of citric acid monohydrate were added to 200 mL of deionized water and heated and stirred in an oil bath at 80 °C for 10 h to allow the three to react fully. The resulting coordination compound precipitated out as a precipitate, which was then separated by filtration to obtain a solution. The total concentration of platinum and nickel in the solution was 0.12 mol / L, and the concentration of citric acid was 0.14 mol / L. The solution was heated and stirred in an oil bath at 80 °C until the solvent evaporated to dryness, and then dried in a forced-air drying oven at 80 °C for 10 h to obtain the precursor material.

[0068] (2) After grinding the precursor material into powder in a mortar, it is transferred to a tube furnace and heated to 600°C at a rate of 4°C / min under a nitrogen atmosphere (flow rate of 80 mL / min). After holding for 3 hours, it is naturally cooled to room temperature and then taken out.

[0069] (3) After grinding the pyrolysis product, for 1g of pyrolysis product, acid wash with 80mL of dilute nitric acid (1mol / L) at 25℃ for 10h, filter, wash with deionized water until the solution pH is neutral, and dry in a 60℃ forced-air drying oven for 12h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0070] The obtained carbon-coated platinum-nickel alloy nanomaterials were subjected to X-ray diffraction analysis, transmission electron microscopy analysis, and X-ray electron energy dispersive spectroscopy analysis, as shown in Figures 1, 2, and 3, respectively.

[0071] As shown in Figure 1, the carbon-coated platinum-nickel alloy nanomaterial exhibits a set of platinum-nickel alloy diffraction peaks between the diffraction peaks of standard platinum (PDF#04-0802) and standard nickel (PDF#04-0850), confirming the formation of the platinum-nickel alloy. Specifically, two diffraction peaks are located in the range of 39.7°–44.7°; the lower-angle peak corresponds to the platinum-rich alloy phase, while the higher-angle peak corresponds to the nickel-rich alloy phase.

[0072] As shown in Figure 2, the material exhibits a clear core-shell structure, with carbon shells coating alloy nanoparticles. The average particle size of the alloy nanoparticles is 3.8 nm. The metal content of the carbon-coated material was determined using ICP-OES, and the contents of carbon, hydrogen, and oxygen were measured using an elemental analyzer. The results are shown in Table 1.

[0073] (4) After mixing carbon-coated platinum-nickel alloy nanomaterials with Ketjen black at a mass ratio of 5:4, the mixture was thoroughly ground in a mortar to obtain fuel cell cathode catalyst CAT-1.

[0074] Example 2

[0075] (1) 1.0 g tetraammineplatinum acetate, 3.6 g nickel acetate tetrahydrate and 1.2 g citric acid monohydrate were added to 120 mL of deionized water and heated and stirred in an oil bath at 80 °C for 10 h to allow the three to react fully and form a light green precipitate. The solution was separated by vacuum filtration. The total concentration of platinum and nickel in the solution was 0.1 mol / L and the concentration of citric acid was 0.02 mol / L. The solvent in the separated solution was then removed by rotary evaporation and dried in a vacuum drying oven at 60 °C for 10 h to obtain the precursor material.

[0076] (2) After grinding the precursor material into powder in a mortar, it is transferred to a tube furnace and heated to 700°C at a nitrogen atmosphere with a nitrogen flow rate of 80 mL / min and a heating rate of 3°C / min for 2 hours. After cooling naturally to room temperature, it is taken out.

[0077] (3) After grinding the pyrolysis product, for 1g of pyrolysis product, acid washing was performed with 80mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 23h. After filtration and washing with deionized water until the solution pH was neutral, the product was placed in a vacuum drying oven and dried at 60℃ for 10h to obtain carbon-coated platinum-nickel alloy nanomaterials. The metal content of the carbon-coated material was determined by ICP-OES, and the content of carbon, hydrogen, and oxygen elements was determined by an elemental analyzer. The results are shown in Table 1.

[0078] (4) After mixing carbon-coated platinum-nickel alloy nanomaterials with Ketjen black at a mass ratio of 5:2, the mixture was thoroughly ground in a mortar to obtain fuel cell cathode catalyst CAT-2.

[0079] Table 1

[0080]

[0081] Example 3

[0082] (1) Mix 1.0 g tetraammineplatinum acetate, 2.6 g cobalt acetate, and 4.0 g citric acid monohydrate, add 150 mL of deionized water, and reflux in an oil bath at 70 °C for 8 h to allow the three to react fully and form a red precipitate. Centrifuge to separate the solution. The total concentration of platinum and cobalt in the solution is 0.08 mol / L, and the concentration of citric acid is 0.1 mol / L. After the solvent in the solution is evaporated to dryness by rotary evaporation, dry it in a forced-air drying oven at 80 °C for 8 h to obtain the precursor material.

[0083] (2) After grinding the precursor material into powder in a mortar, it is heated to 500℃ at a rate of 8℃ / min under an argon atmosphere (flow rate of 70mL / min) and held for 4h. After naturally cooling to room temperature, it is taken out.

[0084] (3) For 1g of pyrolysis product, acid wash with 80mL of dilute hydrochloric acid (1mol / L) at 25℃ for 15h, filter, wash with deionized water until the solution pH is neutral, and dry in an 80℃ forced-air drying oven for 8h to obtain carbon-coated platinum-cobalt alloy nanomaterials.

[0085] (4) After mixing carbon-coated platinum-nickel alloy nanomaterials with Ketjen black at a mass ratio of 5:4, the mixture was thoroughly ground in a mortar to obtain fuel cell cathode catalyst CAT-3.

[0086] Example 4

[0087] The method was followed in Example 1, except that the amount of tetraammineplatinum acetate was 1.0 g, the amount of nickel acetate tetrahydrate was 2.8 g, and the amount of citric acid monohydrate was 6.0 g. The solution was separated by centrifugation, and the total concentration of platinum and nickel in the solution was 0.06 mol / L, and the concentration of citric acid was 0.17 mol / L.

[0088] CAT-4, a cathode catalyst for fuel cells.

[0089] Example 5

[0090] The method is the same as in Example 1, except that in step (3), the pyrolysis conditions are: under a nitrogen atmosphere (flow rate of 110 mL / min), the temperature is raised to 800°C at a rate of 10°C / min and held for 2 hours.

[0091] CAT-5, a cathode catalyst for fuel cells.

[0092] Comparative Example 1

[0093] A commercially available 40% Pt / C catalyst, HISPEC4000, was used as DCAT-1 from JM Company.

[0094] Comparative Example 2

[0095] Following the method in CN116207279A, 1.0 g of tetraammineplatinum acetate, 1.8 g of basic nickel carbonate (with a Ni content of 40.33% by weight), and 4.2 g of citric acid monohydrate were mixed and 200 mL of deionized water was added. The mixture was magnetically stirred for 1 h to ensure complete dissolution. The solution was then heated and stirred in an oil bath at 80 °C. No precipitate formed during the heating and stirring process, indicating that basic nickel carbonate, as a nickel source, cannot form a precipitated complex. Stirring continued until the solvent evaporated completely, and then the solution was dried in a vacuum oven at 60 °C for 12 h to obtain the precursor material.

[0096] The precursor material was ground into powder in a mortar, placed in a porcelain boat, transferred to a tube furnace, and heated to 700°C at a nitrogen atmosphere with a nitrogen flow rate of 80 mL / min and a heating rate of 8°C / min for 2 hours. After naturally cooling to room temperature, it was removed.

[0097] After grinding the pyrolysis product, for 1g of pyrolysis product, acid washing was performed at 90℃ for 23h with 80mL of dilute sulfuric acid (0.5mol / L), filtered, washed with deionized water until the solution pH was neutral, and then dried in a vacuum drying oven at 60℃ for 10h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0098] Carbon-coated platinum-nickel alloy nanomaterials were mixed with Ketjen black at a mass ratio of 5:3 and then thoroughly ground in a mortar to obtain carbon-coated platinum-nickel alloy catalyst DCAT-2.

[0099] Test case

[0100] (1) Electrode preparation: Weigh a certain amount of catalyst sample and disperse it in a mixed solution of water, ethanol / isopropanol and perfluorosulfonic acid (nafion). Sonicate in ice water for 1 hour to form a uniform ink. Use a pipette to take 10 μL of ink and drop it onto the glassy carbon electrode. After natural drying, it can be used for electrochemical testing.

[0101] (2) ORR activity test: 0.1M HClO4 was used as the electrolyte. The electrolyte was aerated for half an hour before the test to obtain an oxygen-saturated or nitrogen-saturated electrolyte. The oxygen-saturated electrolyte was used for LSV testing, and the nitrogen-saturated electrolyte was used for CV testing to determine the electrochemical active area. A standard hydrogen electrode was used as the reference electrode, and a carbon rod as the counter electrode. For LSV testing, the potential range was selected as 0-1.1V vs RHE, the working electrode rotation speed was 1600 rpm, and the scan rate was 10 mV / s. For CV testing, the potential range was selected as 0-1.1V vs RHE, the working electrode rotation speed was 0, and the scan rate was 50 mV / s.

[0102] (3) ORR sulfur poisoning test: 0.1M HClO4 containing 0.1 mmol / L Na2SO3 was used as the electrolyte. After poisoning for 120 s under N2 saturation at a constant voltage of 0.65 V (vs RHE), the electrode was removed and placed in 0.1M HClO4 without Na2SO3. The ORR activity of the poisoned catalyst was tested according to the activity test method. All electrochemical activity calculations used the current density corresponding to 0.9 V.

[0103] The electrocatalytic oxygen reduction resistance to sulfur poisoning of the above-mentioned examples and comparative examples was determined using a rotating disk electrode, and the results are shown in Table 2.

[0104] Table 2

[0105]

[0106]

[0107] As shown in Table 2 and Figure 4, after poisoning, the half-wave potential of Example 1 decreased by only 7 mV; the mass-specific activity decreased from the initial 0.323 A / mg. Pt Decreased by 0.276A / mg Pt The retention rate was 85.45%. As shown in Table 2 and Figure 5, after poisoning, the half-wave potential of Example 2 decreased by only 2 mV; the mass-specific activity decreased from the initial 0.303 A / mg. Pt Decreased by 0.296A / mg Pt The retention rate was 97.69%. Table 2 and Figure 6 show that after poisoning, Comparative Example 1 experienced a half-wave potential loss of 17 mV; the mass-specific activity decreased from the initial 0.178 A / mg. Pt Decreased to 0.136A / mg Pt The retention rate was 76.40%. The antitoxicity test results of the above examples and comparative examples demonstrate that the carbon-coated platinum-nickel alloy nanomaterials provided by the present invention have good anti-sulfur poisoning performance during the catalytic oxygen reduction reaction.

[0108] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a fuel cell cathode catalyst, characterized in that, The preparation method includes: (1) mixing tetraammineplatinum acetate, transition metal acetate, citric acid and solvent under stirring conditions to carry out a coordination reaction, and then separating the solid and liquid to obtain a product solution; wherein the transition metal is selected from at least one of Ni, Co and Zn; (2) removing the solvent from the product solution and then drying it to obtain a precursor material; (3) pyrolyzing the precursor material at high temperature under an inert atmosphere; (4) contacting the product obtained from the high-temperature pyrolysis with acid, and then optionally washing and drying it; (5) mixing the product of step (4) with conductive carbon black.

2. The preparation method according to claim 1, wherein, The transition metal is Ni.

3. The preparation method according to claim 1 or 2, wherein, In step (1), the total molar amount of tetraammineplatinum acetate and transition metal acetate, calculated as metal elements, is in a molar ratio of citric acid to 1:(0.1-5), preferably 1:(0.3-2); preferably, in step (1), the molar ratio of tetraammineplatinum acetate, calculated as platinum, to transition metal acetate, calculated as transition metal elements, is 1:(1-10), preferably 1:(3-7).

4. The preparation method according to any one of claims 1-3, wherein, The total concentration of platinum and transition metals in the product solution is 0.01-0.15 mol / L, and the concentration of citric acid is 0.01-0.2 mol / L.

5. The preparation method according to any one of claims 1-4, wherein, The conditions for the coordination reaction include: a temperature of 40-100℃, preferably 60-80℃, and a time of 3-16h, preferably 6-12h.

6. The preparation method according to any one of claims 1-5, wherein, In step (3), the inert gas is nitrogen and / or argon; preferably, the flow rate of the inert gas is 20-120 mL / min; preferably, the pyrolysis temperature is 400-1000℃, more preferably 500-700℃; preferably, the heating rate of the high-temperature pyrolysis is 2-10℃ / min, more preferably 2-8℃ / min; preferably, the isothermal time of the high-temperature pyrolysis is 1-6 h.

7. The preparation method according to any one of claims 1-6, wherein, In step (4), the acid is provided by an aqueous solution of an acid, preferably, the acid is at least one of sulfuric acid, nitric acid and hydrochloric acid; preferably, the amount of acid used is 40-100 mL relative to 1 g of the pyrolysis product obtained in step (1); preferably, the acid is provided by a sulfuric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C; or, the acid is provided by a nitric acid solution with a concentration of 0.5-15 mol / L and a contact temperature of 25-60°C; or, the acid is provided by a hydrochloric acid solution with a concentration of 0.5-2 mol / L and a contact temperature of 25-90°C; preferably, in step (2), the contact time is 3-50 h.

8. The preparation method according to any one of claims 1-7, wherein, The weight ratio of the product obtained in step (4) to the conductive carbon black is 1:0.1-5, preferably 1:0.1-1; preferably, the conductive carbon black is selected from Ketjen black and / or Cabot carbon black.

9. A fuel cell cathode catalyst prepared by the preparation method according to any one of claims 1-8.

10. A method for improving the sulfur poisoning resistance of a proton exchange membrane fuel cell cathode, the method comprising: The fuel cell cathode catalyst according to claim 9 is used.

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