Cathode catalyst of proton exchange membrane fuel cell as well as preparation method and application of cathode catalyst

Abstract

The invention relates to the technical field of fuel cell cathode catalysts, and discloses a proton exchange membrane fuel cell cathode catalyst and a preparation method and application thereof.The preparation method comprises the steps that 1, tetraammineplatinum acetate, M metal acetate, citric acid and a solvent are mixed under the stirring condition and subjected to a coordination reaction, and a coordination solution is obtained; a coordination reaction product containing the coordination compound is obtained; wherein M is selected from at least one of Ni, Co and Zn; (2) performing high-temperature pyrolysis on the coordination reaction product in an inert atmosphere; and (3) contacting the product obtained in the step (2) with acid, and then carrying out solid-liquid separation, washing and drying to obtain the carbon-coated platinum-based alloy nano material, and (4) mixing the carbon-coated platinum-based alloy nano material with conductive carbon black. The proton exchange membrane fuel cell cathode catalyst prepared by the invention has excellent sulfur poisoning resistance and good stability.

Description

Proton exchange membrane fuel cell cathode catalyst, its preparation method and application Technical Field

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

[0002] Proton exchange membrane fuel cells (PEMFCs) directly convert the chemical energy of hydrogen and oxidant into electrical energy through electrochemical reactions. They offer advantages such as rapid start-up, high energy conversion efficiency, and low pollution, making them a promising new energy technology. Currently, the oxygen reduction reaction catalyst at the cathode of PEMFCs relies on the precious metal platinum. However, even trace amounts of sulfides can poison the platinum catalyst during catalysis, reducing its catalytic activity and consequently affecting fuel cell performance. Since the air used at the cathode of PEMFCs inevitably contains trace amounts of sulfur compounds, developing sulfur-resistant catalysts is crucial for the development of PEMFCs.

[0003] Current research directions for fuel cell anti-poisoning catalysts mainly include platinum-based modified catalysts, non-precious metal catalysts, and metal-free carbon-based catalysts. Compared with the other two methods, platinum-based modified catalysts exhibit higher catalytic activity and are currently the optimal choice for sulfur poisoning resistance in fuel cells. However, platinum-based modified catalysts cannot completely prevent platinum from contacting sulfur-containing poisons, and the catalyst still faces the risk of poisoning as the reaction proceeds. Therefore, new anti-poisoning strategies need to be designed to further improve the catalyst's anti-poisoning performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of poor sulfur poisoning resistance and insufficient catalytic activity of oxygen reduction reaction catalysts in proton exchange membrane fuel cell cathodes in the prior art, and to provide a proton exchange membrane fuel cell cathode catalyst, its preparation method and application. The proton exchange membrane fuel cell cathode catalyst prepared by this method has excellent sulfur poisoning resistance.

[0005] To achieve the above objectives, the present invention provides a method for preparing a proton exchange membrane fuel cell cathode catalyst, comprising the following steps:

[0006] (1) Under stirring conditions, tetraammineplatinum acetate, M metal acetate, citric acid and solvent are mixed to carry out a coordination reaction to obtain a coordination reaction product containing a coordination compound.

[0007] Wherein, M is selected from at least one of Ni, Co and Zn;

[0008] (2) The coordination reaction product is subjected to high-temperature pyrolysis under an inert atmosphere;

[0009] (3) The product obtained in step (2) is contacted with acid, and then solid-liquid separation, washing and drying are performed to obtain carbon-coated platinum-based alloy nanomaterials.

[0010] (4) Mix carbon-coated platinum-based alloy nanomaterials with conductive carbon black.

[0011] The second aspect of the present invention provides a proton exchange membrane fuel cell cathode catalyst prepared by the above preparation method.

[0012] The third aspect of the present invention provides the application of the above-described proton exchange membrane fuel cell cathode catalyst in a proton exchange membrane fuel cell.

[0013] The method for preparing a proton exchange membrane fuel cell cathode catalyst provided by this invention utilizes a coordination compound obtained by the coordination reaction of tetraammineplatinum, M metal acetate, and citric acid as a pyrolysis precursor. During pyrolysis, this precursor can promote the alloying of platinum and metal M, and simultaneously form a carbon shell on the alloy surface. This can enhance catalytic activity through induction and strain effects, and prevent sulfur-containing poisons from contacting the core platinum-nickel alloy nanoparticles, thus exhibiting excellent anti-sulfur poisoning performance and good catalyst stability. Attached Figure Description

[0014] Figure 1 is the XRD pattern of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0015] Figure 2 is a TEM image of the carbon-coated platinum-nickel alloy nanomaterials prepared in Example 1;

[0016] Figure 3 is a comparison of the LSV curves of the catalyst prepared in Example 1 before and after poisoning in the catalytic oxygen reduction reaction;

[0017] Figure 4 is a comparison of the LSV curves of the catalyst prepared in Example 2 before and after poisoning of the oxygen reduction reaction.

[0018] Figure 5 is a comparison of the LSV of the catalyst prepared in Comparative Example 1 before and after poisoning in the catalytic oxygen reduction reaction. Detailed Implementation

[0019] 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.

[0020] The first aspect of this invention provides a method for preparing a proton exchange membrane fuel cell cathode catalyst, characterized by comprising the following steps:

[0021] (1) Under stirring conditions, tetraammineplatinum acetate, M metal acetate, citric acid and solvent are mixed to carry out a coordination reaction to obtain a coordination reaction product containing a coordination compound.

[0022] Wherein, M is selected from at least one of Ni, Co and Zn;

[0023] (2) The coordination reaction product is subjected to high-temperature pyrolysis under an inert atmosphere;

[0024] (3) The product obtained in step (2) is contacted with acid, and then solid-liquid separation, washing and drying are performed to obtain carbon-coated platinum-based alloy nanomaterials.

[0025] (4) Mix carbon-coated platinum-based alloy nanomaterials with conductive carbon black.

[0026] In this invention, tetraammineplatinum acetate, M metal acetate, and citric acid are all commercially available. The M metal acetate and / or citric acid may also contain water of crystallization, as is well known to those skilled in the art.

[0027] In this invention, tetraammineplatinum acetate, metal M acetate, and citric acid can promote a coordination reaction between tetraammineplatinum, metal M, and citric acid, resulting in a coordination compound that precipitates out in the form of a precipitate. The molecular structure of the coordination compound is analyzed by single-crystal X-ray diffraction. The coordination compound includes a cation as shown in formula (1) and an anion as shown in formula (2).

[0028]

[0029] M is selected from at least one of Ni, Co and Zn.

[0030] In this invention, the molecular structure of the coordination compound was determined by single-crystal X-ray diffraction. The testing equipment used was Rigaku Corporation, Japan, XtaLAB PRO 007HF, and the testing conditions were: radiation: Mo Kα (0.71037 × 10⁻⁶). - 1 nm), voltage: 50kV, current: 24mA, ambient temperature: 24℃, ambient humidity: 40%.

[0031] According to some preferred embodiments of the present invention, in step (1), the molar ratio of tetraammineplatinum acetate (calculated as platinum) to metal acetate (calculated as element M) is 1:(1-25), preferably 1:(4-12).

[0032] According to some preferred embodiments of the present invention, in step (1), the total molar amount of tetraammineplatinum acetate and M metal acetate, calculated as metal elements, is in a molar ratio of citric acid to 1:(0.1-5), preferably 1:(0.3-2).

[0033] 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, M 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.

[0034] 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 3-12 hours, more preferably 6-10 hours. Adopting the above preferred embodiments is beneficial for the formation of coordination compounds.

[0035] In this invention, the precipitate product can be separated from the product of the coordination reaction by any solid-liquid separation method, that is, the coordination compound can be obtained. For example, filtration, vacuum filtration, centrifugation, etc. can be used, and those skilled in the art can choose according to their needs.

[0036] According to the present invention, step (1) may optionally further include drying the precipitate obtained by the coordination reaction. The present invention does not particularly limit the drying method and conditions, and conventional methods in the art can be used. Preferably, the drying is vacuum drying, the drying temperature is 50-100°C, and the drying time is 6-14 hours.

[0037] According to the present invention, the precipitate obtained in step (1) can promote the alloying of platinum and metal M during the pyrolysis process, and form a carbon shell on the alloy surface to form carbon-coated platinum-based alloy nanomaterials. The graphene shell in the carbon-coated platinum-nickel alloy nanomaterials can effectively isolate the poisons from the core platinum-based alloy particles, thereby improving the catalyst's resistance to poisoning and exhibiting good anti-sulfur poisoning performance during the catalytic process.

[0038] In this invention, in step (2), 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.

[0039] Preferably, the flow rate of the inert gas is 20-120 mL / min, and more preferably 60-100 mL / min.

[0040] 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 500-800℃.

[0041] 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.

[0042] Preferably, the isothermal time for the high-temperature pyrolysis is 1-6 hours, and more preferably 2-5 hours.

[0043] After the above-mentioned high-temperature pyrolysis, it is preferable to let the pyrolysis product cool naturally in an inert atmosphere, then grind it appropriately, and then perform subsequent acid washing.

[0044] According to the present invention, in step (3), the purpose of contacting the product obtained in step (2) 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.

[0045] Preferably, the amount of acid used is 40-100 mL, more preferably 40-80 mL, relative to 1 g of the pyrolysis product obtained in step (2).

[0046] According to some preferred embodiments of the present invention, in step (3), 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.

[0047] Preferably, in step (3), the contact time is 3-50 hours, more preferably 3-24 hours.

[0048] According to the present invention, in step (3), 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.

[0049] According to the present invention, in step (3), the purpose of drying 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.

[0050] According to the present invention, Pt and metal M exist in the carbon-coated platinum-based alloy nanomaterial obtained in step (3) in alloy form. Preferably, the XRD pattern of the carbon-coated platinum-based alloy nanomaterial contains only characteristic diffraction peaks of the alloy and no characteristic diffraction peaks of Pt or metal M. This can be determined by X-ray diffraction. X-ray diffraction was performed on an Empyrean imaging device from Malvern Panaco GmbH in the Netherlands. The test conditions were: Cu target, Kα rays, tube voltage 40 kV, tube current 40 mA, and scan rate 2° / min.

[0051] Preferably, when M is Ni, the XRD spectrum of the carbon-coated platinum-based alloy nanomaterial has characteristic diffraction peaks at 2θ of 42.5±1°, 49.6±1°, and 72.6±1°, and there are no characteristic diffraction peaks of Pt and / or Ni elements.

[0052] Preferably, when M is Co, the XRD spectrum of the carbon-coated platinum-based alloy nanomaterial has characteristic diffraction peaks at 2θ of 40.0±0.5°, 46.6±0.5°, and 67.9±0.5°, and there are no characteristic diffraction peaks of Pt and / or Co elements.

[0053] Preferably, the average particle size of the platinum-metal M alloy particles is 3-6 nm.

[0054] In this invention, the average particle size of the alloy particles is measured by electron microscopy statistical method, with no less than 200 particles counted, and then the average particle size is calculated.

[0055] Preferably, in the carbon-coated platinum-based alloy nanomaterial, the carbon content is 5-20% by weight, preferably 10-20% by weight; the platinum content is 40-65% by weight, preferably 50-65% by weight; the content of metallic M is 10-30% by weight, preferably 15-25% by weight; the hydrogen content is 0.5-1.5% by weight, preferably 0.7-1.3% by weight; and the oxygen content is 1-15% by weight, preferably 5-12% by weight.

[0056] 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.

[0057] The content of 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.

[0058] In this invention, there is no particular limitation on the conductive carbon black, which can be obtained commercially. Any conductive carbon black that can be used for oxygen reduction reaction at the cathode of a fuel cell can be used in this invention, such as Ketjen black (e.g., ECT-600JD), Cabot carbon black (e.g., Vulcan XC 72), etc.

[0059] According to some preferred embodiments of the present invention, the weight ratio of the carbon-coated platinum-based alloy nanomaterial to the conductive carbon black is 1:0.1-5, preferably 1:0.1-1.

[0060] The second aspect of the present invention provides a proton exchange membrane fuel cell cathode catalyst prepared by the above preparation method.

[0061] According to the present invention, the proton exchange membrane fuel cell cathode catalyst comprises carbon-coated platinum-based alloy nanomaterials and conductive carbon black. The definitions of the carbon-coated platinum-based alloy nanomaterials and conductive carbon black are the same as in the first aspect and will not be repeated here.

[0062] The third aspect of the present invention provides the application of the above-described proton exchange membrane fuel cell cathode catalyst in a proton exchange membrane fuel cell.

[0063] The air used for the cathode of a proton exchange membrane fuel cell inevitably contains trace amounts of sulfur compounds. The cathode catalyst of the proton exchange membrane fuel cell has excellent resistance to sulfur poisoning and good activity stability.

[0064] The present invention will be described in detail below through embodiments.

[0065] In the following examples, unless otherwise specified, all reagents used in this invention are of analytical grade and are commercially available.

[0066] The molecular structure of the coordination compound was determined by single-crystal X-ray diffraction. The testing equipment used was Rigaku Corporation XtaLAB PRO 007HF, and the testing conditions were: radiation: Mo Kα (0.71037×10-1nm), voltage: 50kV, current: 24mA, ambient temperature: 24℃, and ambient humidity: 40%.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Example 1

[0072] (1) 1.0 g of tetraammineplatinum acetate, 7.6 g of nickel acetate tetrahydrate, and 7.2 g of citric acid monohydrate were added to 200 mL of deionized water and stirred at an oil bath at 80 °C for 10 h to allow the three to react fully and form a light green precipitate. The precipitate was separated by filtration and dried in a forced-air drying oven at 60 °C for 10 h to obtain the precursor material. Single-crystal X-ray diffraction analysis of the precursor material determined it to be a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0073] (2) Grind the precursor material into powder in a mortar, put it into a porcelain boat, transfer it to a tube furnace, and heat it to 700°C at a rate of 6°C / min under a nitrogen atmosphere (flow rate of 100 mL / min) and hold for 2 hours. After naturally cooling to room temperature, take it out.

[0074] (3) After grinding the pyrolysis product, for 1g of pyrolysis product, acid wash with 80mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 23h, filter, wash with deionized water until the solution pH is neutral, and put it in a vacuum drying oven at 60℃ for 10h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0075] The metal content of the carbon-coated material was determined by ICP-OES, and the contents of carbon, hydrogen, and oxygen were determined by an elemental analyzer. Based on the total amount of carbon-coated platinum-nickel alloy nanomaterials, after normalization, the platinum content was 61.33 wt%, the nickel content was 15.33 wt%, the carbon content was 12.86 wt%, the hydrogen content was 1.15 wt%, and the oxygen content was 9.33 wt%.

[0076] X-ray diffraction analysis of carbon-coated platinum-nickel alloy nanomaterials is shown in Figure 1. It can be seen that the diffraction peaks of the carbon-coated platinum-nickel alloy nanomaterials are located between the diffraction peaks of standard platinum (PDF#04-0802) and standard nickel (PDF#04-0850), corresponding to the (111) and (200) planes of the face-centered cubic structure, proving the formation of the platinum-nickel alloy.

[0077] Transmission electron microscopy analysis of carbon-coated platinum-nickel alloy nanomaterials, as shown in Figure 2, reveals a clear core-shell structure. The outer carbon shell encapsulates the inner alloy nanoparticles, with an average particle size of 5.4 nm.

[0078] (4) After mixing carbon-coated platinum-nickel alloy nanomaterials with Ketjen black at a mass ratio of 5:3, the mixture was thoroughly ground in a mortar to obtain carbon-coated platinum-nickel alloy catalyst CAT-1.

[0079] Example 2

[0080] (1) 1.5 g of tetraammineplatinum acetate, 8.2 g of nickel acetate tetrahydrate, and 10.6 g of citric acid monohydrate were added to 150 mL of deionized water and stirred at a constant temperature of 60 °C in an oil bath for 12 h to allow the three to react fully and form a light green precipitate. The precipitate was separated by centrifugation and dried at 70 °C for 8 h in a forced-air drying oven to obtain the precursor material. Single-crystal X-ray diffraction analysis of the precursor material was performed to determine that the crystal structure of the precursor material was a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0081] (2) After grinding the precursor material into powder in a mortar, the temperature was raised to 650°C at a rate of 3°C / min under an argon atmosphere with an argon flow rate of 100 mL / min. After holding for 4 hours, the temperature was naturally cooled to room temperature and then removed.

[0082] (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 a 70℃ forced-air drying oven for 8h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0083] The metal content of the carbon-coated material was determined by ICP-OES, and the contents of carbon, hydrogen, and oxygen were determined by an elemental analyzer. Based on the total amount of carbon-coated platinum-nickel alloy nanomaterials, after normalization, the platinum content was 60.86 wt%, the nickel content was 17.65 wt%, the carbon content was 13.23 wt%, the hydrogen content was 0.73 wt%, and the oxygen content was 7.53 wt%.

[0084] (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 carbon-coated platinum-nickel alloy catalyst CAT-2.

[0085] Example 3

[0086] (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. Filter to separate the precipitate, and dry the precipitate in a vacuum oven at 60 °C for 12 h to obtain the precursor material. Single-crystal X-ray diffraction analysis of the precursor material determined that the crystal structure of the precursor material is a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), where M is Co.

[0087] (2) Grind the precursor material into powder in a mortar, put it into a porcelain boat, transfer it to a tube furnace, and raise it to 600℃ at a nitrogen atmosphere with a nitrogen flow rate of 80 mL / min and hold it for 4 hours. After naturally cooling to room temperature, take it out.

[0088] (3) After grinding the pyrolysis product, for 1g of pyrolysis product, acid wash with 80mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 23h, filter, wash with deionized water until the solution pH is neutral, and dry in a forced-air drying oven at 70℃ for 10h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0089] (4) After mixing carbon-coated platinum-nickel alloy nanomaterials with Ketjen black at a mass ratio of 5:3, the mixture was thoroughly ground in a mortar to obtain carbon-coated platinum-nickel alloy catalyst CAT-3.

[0090] Example 4

[0091] (1) 1.5 g of tetraammineplatinum acetate, 2.9 g of nickel acetate tetrahydrate, and 1.0 g of citric acid monohydrate were added to 150 mL of deionized water and stirred at a constant temperature of 70 °C in an oil bath for 10 h to allow the three to react fully and form a light green precipitate. The precipitate was separated by centrifugation and dried at 70 °C for 8 h in a forced-air drying oven to obtain the precursor material. Single-crystal X-ray diffraction analysis of the precursor material was performed to determine that the crystal structure of the precursor material was a coordination compound containing a cation as shown in formula (1) and an anion as shown in formula (2), wherein M is Ni.

[0092] (2) After grinding the precursor material into powder in a mortar, the temperature was raised to 650°C at a rate of 8°C / min under an argon atmosphere with an argon flow rate of 120 mL / min. After holding for 4 hours, the temperature was naturally cooled to room temperature and then removed.

[0093] (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 a 70℃ forced-air drying oven for 8h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0094] (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 carbon-coated platinum-nickel alloy catalyst CAT-4.

[0095] Comparative Example 1

[0096] Purchased commercially from JM Company 40% Pt / C catalyst (brand name: HISPEC4000).

[0097] Comparative Example 2

[0098] (1) 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 completely dissolve the solvent. The mixture was then heated and stirred in an oil bath at 80 °C. No precipitate was formed during the heating and stirring process, indicating that basic nickel carbonate as a nickel source could not form a precipitated complex. Stirring was continued until the solvent evaporated to dryness, and then the mixture was dried in a vacuum oven at 60 °C for 12 h to obtain the precursor material.

[0099] (2) Grind the precursor material into powder in a mortar, put it into a porcelain boat, transfer it to a tube furnace, and raise it to 700°C at a nitrogen atmosphere with a nitrogen flow rate of 80 mL / min and hold it for 2 hours. After naturally cooling to room temperature, take it out.

[0100] (3) After grinding the pyrolysis product, for 1g of pyrolysis product, acid wash with 80mL of dilute sulfuric acid (0.5mol / L) at 90℃ for 23h, filter, wash with deionized water until the solution pH is neutral, and put it in a vacuum drying oven at 60℃ for 10h to obtain carbon-coated platinum-nickel alloy nanomaterials.

[0101] (4) After mixing carbon-coated platinum-nickel alloy nanomaterials with Ketjen black at a mass ratio of 5:3, the mixture was thoroughly ground in a mortar to obtain carbon-coated platinum-nickel alloy catalyst DCAT-1.

[0102] Comparative Example 3

[0103] 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 added to 200 mL of deionized water. The mixture was magnetically stirred for 2 hours to completely dissolve the precipitate. Then, 1 g of acetic acid was added, and the mixture was refluxed in an oil bath at 80 °C for 8 hours. No precipitate was formed during the heating and stirring process, so the catalyst could not be synthesized.

[0104] Test case

[0105] (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.

[0106] (2) ORR activity test: 0.1M HClO4 was used as the electrolyte. Aeration was performed 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 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 0-1.1V vs RHE, the working electrode rotation speed was 0, and the scan rate was 50 mV / s.

[0107] (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.

[0108] 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 1.

[0109] The LSV curves of the catalytic oxygen reduction reaction before and after sulfur poisoning in Examples 1, 2 and Comparative Example 1 are shown in Figures 3, 4 and 5, respectively.

[0110] Table 1

[0111]

[0112]

[0113] As can be seen from the results in Table 1, the catalyst provided by the present invention has good resistance to sulfur poisoning when catalyzing oxygen reduction reaction.

[0114] 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 proton exchange membrane fuel cell cathode catalyst, characterized in that, Includes the following steps: (1) Under stirring conditions, tetraammineplatinum acetate, M metal acetate, citric acid and solvent are mixed to carry out a coordination reaction to obtain a coordination reaction product containing a coordination compound; wherein, M is selected from at least one of Ni, Co and Zn; (2) The coordination reaction product is subjected to high-temperature pyrolysis under an inert atmosphere. (3) Contact the product obtained in step (2) with acid, and then perform solid-liquid separation, washing and drying to obtain carbon-coated platinum-based alloy nanomaterials; (4) Mix the carbon-coated platinum-based alloy nanomaterials with conductive carbon black.

2. The preparation method according to claim 1, wherein, In step (1), the coordination compound includes a cation as shown in formula (1) and an anion as shown in formula (2). M is selected from at least one of Ni, Co and Zn.

3. The preparation method according to claim 1 or 2, wherein, In step (1), the molar ratio of tetraammineplatinum acetate (calculated as platinum) to metal acetate (calculated as element M) is 1:(1-25), preferably 1:(4-12); preferably, in step (1), the molar ratio of the total molar amount of tetraammineplatinum acetate and metal acetate (calculated as element M) to citric acid is 1:(0.1-5), preferably 1:(0.3-2).

4. The preparation method according to any one of claims 1-3, wherein, In step (1), the conditions for the coordination reaction include: a temperature of 40-100℃, preferably 60-80℃, and a time of 3-12h, preferably 4-8h.

5. The preparation method according to any one of claims 1-4, wherein, In step (2), the inert gas is nitrogen and / or argon; preferably, the flow rate of the inert gas is 20-120 mL / min.

6. The preparation method according to any one of claims 1-5, wherein, In step (2), the temperature of the high-temperature pyrolysis is 400-1000℃; preferably, the heating rate of the high-temperature pyrolysis is 2-10℃ / min; preferably, the isothermal time of the high-temperature pyrolysis is 1-6h.

7. The preparation method according to any one of claims 1-6, wherein, In step (3), 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 product obtained in step (2); 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 (3), 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 carbon-coated platinum-based alloy nanomaterial 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 proton exchange membrane fuel cell cathode catalyst prepared by the preparation method according to any one of claims 1-8.

10. The application of the proton exchange membrane fuel cell cathode catalyst according to claim 9 in a proton exchange membrane fuel cell.

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