A platinum-based multi-metal catalyst and its preparation method and use

Abstract

The present invention provides a platinum-based multi-metal catalyst and a preparation method and use thereof. The preparation method comprises: dissolving a platinum precursor, a transition metal precursor, a free radical quencher precursor and a carbon material in a solvent to form a reaction slurry, subjecting the reaction slurry to a reduction reaction under microwave irradiation to obtain a catalyst precursor, and then subjecting the catalyst precursor to an alloying treatment to obtain the platinum-based multi-metal catalyst. The platinum-based multi-metal catalyst obtained by the preparation method provided by the present invention can achieve the technical effect of improving the oxygen reduction activity of the catalyst, reducing the production cost of the catalyst, and improving the durability of the fuel cell through the interaction between the platinum transition metal alloy particles and the free radical quencher particles.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy nanomaterials, and in particular relates to a platinum-based multi-metal catalyst and a preparation method and use thereof. Background Art

[0002] Proton exchange membrane fuel cells can directly convert chemical energy into electrical energy. A hydrogen oxidation reaction (HOR) occurs at the anode to produce hydrogen ions and electrons; an oxygen reduction reaction (ORR) occurs at the cathode to generate water. However, the ORR kinetic process is extremely slow, and a catalyst is needed to reduce the reaction energy barrier and accelerate the reaction process. The most commonly used catalyst is a platinum-carbon catalyst with high electrochemical activity and stability. However, due to the scarcity of platinum reserves, the catalyst is expensive, which affects the commercialization of fuel cells.

[0003] At present, the Pt-M bond in the alloy formed by 3d transition metals and platinum can enhance the adsorption of reactant oxygen, which is beneficial to improve the reaction activity of the catalyst, reduce the amount of platinum, and thus reduce the cost of the catalyst. However, transition metal elements will produce more hydrogen peroxide intermediates in the ORR process, forming free radicals that attack the organic functional groups in the proton exchange membrane, reduce its mechanical properties and proton conductivity, and lead to poor durability of the proton exchange membrane.

[0004] CN111129508A discloses a transition metal-doped platinum-carbon catalyst and its preparation method and use. The method comprises: mixing a carbon material, a platinum precursor solution and a transition metal salt to obtain a mixed solution; mixing the obtained mixed solution with a reducing agent, separating, and drying to obtain a precursor material; heat-treating the obtained precursor material to obtain transition metal-doped platinum-based nanoparticles; mixing the obtained transition metal-doped platinum-based nanoparticles with a perfluorosulfonic acid solution, separating, and drying to obtain the catalyst. The transition metal-doped platinum-carbon catalyst is coated with a perfluorosulfonic acid membrane to form a continuous proton conduction network, thereby increasing the current density.

[0005] CN110265680A discloses a high-performance transition metal-containing catalyst, a preparation method and its application, wherein a transition metal or its oxide is doped into a carbon material as an electronic conductor, and then platinum nanowires are loaded on its surface to form a high-performance platinum catalyst. The transition metal and platinum in the transition metal-containing catalyst form a synergistic effect, which reduces the amount of platinum used and improves the performance of the fuel cell.

[0006] CN112825357A discloses a Pt-based multi-component transition metal alloy nano electrocatalyst and its preparation and application. The preparation method comprises: dispersing a conductive carbon carrier in a polyol solution and adjusting the pH value of the solution; dissolving a platinum precursor and a transition metal precursor in the same polyol solution and adjusting the pH value of the solution; uniformly mixing the polyol solution of the platinum precursor and the transition metal precursor with the conductive carbon polyol solution to obtain a powdered catalyst precursor; heating and activating the powdered catalyst precursor in a reducing atmosphere to obtain a PtM / C alloy catalyst. The nano catalyst has a high degree of alloying and good catalytic activity.

[0007] The above documents have improved platinum-carbon catalysts by doping transition metals, but they have not effectively solved the problem that transition metals produce hydrogen peroxide intermediates during the oxygen reduction process, forming free radicals that attack the proton exchange membrane, resulting in a reduction in the life of the fuel cell. Therefore, it is urgent to develop a transition metal platinum-based catalyst that can simultaneously improve the activity of fuel cell catalysts and the durability of fuel cells. Summary of the invention

[0008] In view of the deficiencies in the prior art, the object of the present invention is to provide a platinum-based multi-metal catalyst and a preparation method and use thereof. The platinum-based multi-metal catalyst obtained by the preparation method provided by the present invention can achieve the technical effect of simultaneously improving the oxygen reduction activity of the catalyst and the durability of the fuel cell through the interaction between the platinum transition metal alloy particles and the free radical quencher particles.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0011] A platinum precursor, a transition metal precursor, a free radical quencher precursor and a carbon material are dissolved in a solvent to form a reaction slurry, the reaction slurry is subjected to a reduction reaction under microwave irradiation to obtain a catalyst precursor, and then the catalyst precursor is subjected to an alloying treatment to obtain the platinum-based multi-metal catalyst.

[0012] The platinum-based multi-metal catalyst prepared by the present invention contains a carbon carrier, and platinum transition metal alloy particles and free radical quencher particles (cerium oxide or manganese dioxide) supported on the carbon carrier, wherein the platinum transition metal alloy particles can enhance the adsorption of reactant oxygen, which is beneficial to improving the reaction activity of the catalyst, and the free radical quencher particles can effectively alleviate the damage of the free radicals generated by the transition metal during the reaction to the proton exchange membrane, thereby improving the reaction activity of the catalyst, reducing the production cost of the catalyst, and increasing the life of the proton exchange membrane, thereby improving the durability of the fuel cell.

[0013] At the same time, the present invention uses a reducing solvent to reduce the reaction slurry under microwave irradiation, wherein microwaves are electromagnetic waves, and their propagation speed is the same as the speed of light. When used as heating energy, the material can generate a thermal effect through molecular polarization, friction, collision, etc. in an extremely short time to reach the temperature required for the reaction, making the temperature distribution of the material more uniform, not only making the reduction reaction more efficient, but also making the distribution of nanoparticles on the catalyst carrier more uniform, thereby effectively solving the problem that the traditional heating method has a slow heat transfer rate and is prone to uneven temperature distribution of the reaction slurry, which has an adverse effect on the performance of the catalyst.

[0014] In addition, under microwave irradiation, the platinum precursor and the transition metal precursor undergo reduction reactions to form platinum particles and transition metal particles, respectively, while the free radical quencher precursor does not undergo reduction but exists in the form of an oxide. Therefore, the catalyst precursor obtained by the present invention includes a carbon material carrier, and platinum particles, transition metal particles and free radical quencher particles (cerium oxide or manganese dioxide) located on the carbon carrier.

[0015] The platinum-based multi-metal catalyst obtained by the preparation method provided by the present invention can achieve the technical effect of improving the oxygen reduction activity of the catalyst, reducing the production cost of the catalyst, and improving the durability of the fuel cell through the interaction between the platinum transition metal alloy particles and the free radical quencher particles.

[0016] As a preferred technical solution of the present invention, the preparation process of the reaction slurry includes:

[0017] The platinum precursor, the transition metal precursor and the free radical quencher precursor are dissolved in a solvent to form a mixed solution, and then the carbon material is added to the mixed solution for shear emulsification to obtain the reaction slurry.

[0018] The present invention first dissolves the platinum precursor, the transition metal precursor and the free radical quencher precursor in a solvent to form a uniform mixed solution, and then adds the carbon material for shear emulsification, which is beneficial to improving the dispersion uniformity of the platinum precursor, the transition metal precursor and the free radical quencher precursor on the carbon material, and is subsequently beneficial to exerting the interaction between the platinum transition metal alloy particles and the free radical quencher particles.

[0019] Preferably, a base is also added to the mixed solution.

[0020] The present invention adds a proper amount of alkali to the mixed solution because the alkali can first form hydroxides with the platinum precursor and the transition metal precursor, and the hydroxides have lower redox potentials and weaker oxidizing properties, and are more easily reduced in solvent systems with weaker reducing properties (e.g., ethylene glycol systems).

[0021] Preferably, the base comprises sodium hydroxide and / or potassium hydroxide.

[0022] As a preferred technical solution of the present invention, the molar ratio of the platinum precursor, the transition metal precursor and the free radical quencher precursor is 1:(0.1-1):(0.01-0.1), for example, it can be 1:0.1:0.01, 1:0.2:0.02, 1:0.3:0.03, 1:0.4:0.04, 1:0.5:0.05, 1:0.6:0.06, 1:0.7:0.07, 1:0.8:0.08, 1:0.9:0.09, 1:1:0.1 or 1:0.4:0.06, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] The present invention limits the molar ratio of the platinum precursor, the transition metal precursor and the free radical quencher precursor to 1: (0.1-1): (0.01-0.1). This is because the working environment of the fuel cell is acidic, and the transition metal is easily dissolved and lost in the acidic environment. Therefore, if the transition metal content is too high, the catalyst will have poor chemical stability and short life; while if the transition metal content is too low, the effect of reducing the amount of platinum used in the catalyst is not obvious. At the same time, the addition of the free radical quencher will sacrifice a certain degree of catalyst performance to improve the life of the proton exchange membrane, so its addition amount needs to take into account the performance of the catalyst and the performance of the proton exchange membrane.

[0024] Preferably, the platinum precursor includes any one of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, ammonium chloroplatinate, potassium chloroplatinite, sodium chloroplatinite or platinum acetylacetonate, or a combination of at least two thereof.

[0025] Preferably, the transition metal precursor includes any one of nitrates, sulfates, acetylacetonates or chlorides of transition metals, or a combination of at least two thereof.

[0026] Preferably, the transition metal in the transition metal precursor includes any one of cobalt, nickel, iron or copper.

[0027] Preferably, the free radical quencher precursor includes any one of cerium nitrate, manganese nitrate, cerium chloride or manganese chloride.

[0028] Preferably, the solvent includes any one of ethanol, ethylene glycol or isopropanol, or a combination of at least two of them.

[0029] The solvents in the present invention are all reducing solvents, so that the platinum precursor and the transition metal precursor can be reduced under microwave irradiation.

[0030] Preferably, the carbon material comprises activated carbon material.

[0031] Preferably, the activated carbon material includes any one of XC-72R, Ketjen Black EC-300J, Ketjen Black EC-600J, carbon nanotubes, nanographite powder, and graphene, or a combination of at least two thereof.

[0032] Preferably, the concentration of the carbon material in the solvent is 0.5 to 10 mg / mL, for example, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL, 6 mg / mL, 7 mg / mL, 8 mg / mL, 9 mg / mL or 10 mg / mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] As a preferred technical solution of the present invention, the rotation speed of the shear emulsification is 8000-13000 rpm / min, for example, it can be 8000 rpm / min, 9000 rpm / min, 10000 rpm / min, 11000 rpm / min, 12000 rpm / min or 13000 rpm / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, the shear emulsification time is 0.5 to 6 h, for example, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h or 6 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the pH of the reaction slurry is 10-13, for example, 10, 10.5, 11, 11.5, 12, 12.5 or 13, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] The present invention adjusts the pH of the reaction slurry to 10-13 by adjusting the amount of alkali added in the mixed solution.

[0037] As a preferred technical solution of the present invention, the temperature of the microwave irradiation is 130-190°C, for example, it can be 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C or 190°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] The reaction slurry is placed in a microwave reactor for microwave irradiation. The present invention limits the temperature of microwave irradiation to 130-190°C. When the temperature is lower than 130°C, the platinum precursor and the transition metal precursor cannot be reduced. This is because the temperature is too low and cannot reach the temperature required for the reduction reaction of the two. When the temperature is higher than 190°C, the platinum particles and transition metal particles generated by the reduction reaction will agglomerate. This is because the metal nanoparticles will agglomerate in a short time at an excessively high temperature, thereby reducing the catalytic activity.

[0039] Preferably, the microwave irradiation time is 2 to 60 min, for example, it can be 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, after the microwave irradiation, filtering, washing and vacuum drying are performed in sequence to obtain the catalyst precursor.

[0041] Preferably, the endpoint of the filtration and washing is that the conductivity of the filtrate is ≤5μS / cm, for example, it can be 5μS / cm, 4.5μS / cm, 4μS / cm, 3.5μS / cm, 3μS / cm, 2.5μS / cm or 2μS / cm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] The present invention defines the endpoint of filtration and washing as the conductivity of the filtrate ≤ 5 μS / cm. This is because ions in the metal precursor, such as chloride ions, nitrate ions, sulfate ions, etc., if not cleaned thoroughly, will be adsorbed on the active sites of the catalyst and shield the catalytic activity. Therefore, it is necessary to strictly control the conductivity of the filtrate during the cleaning stage to determine whether the ion content in the catalyst meets the standard.

[0043] As a preferred technical solution of the present invention, the temperature of the alloying treatment is 500-1200°C, for example, it can be 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] The present invention places the catalyst precursor in a tube furnace for alloying treatment. In addition, during the alloying treatment, the platinum particles and transition metal particles in the catalyst precursor form an alloy, and the alloying treatment does not affect the free radical quencher particles, which still exist in an oxidized form (cerium oxide or manganese dioxide). This is because the condition for forming an alloy is that the melting points of the two materials are similar, wherein the melting points of platinum and transition metals (cobalt, nickel, iron or copper) are around 1500°C, and the melting points are close, while the melting points of cerium oxide are 2397°C and manganese dioxide are 535°C, which are greatly different from the melting points of platinum and transition metals, and cannot form an alloy.

[0045] Preferably, the alloying treatment time is 0.5 to 12 h, for example, it can be 0.5 h, 1 h, 2 h, 0.5 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the alloying treatment is performed under a protective atmosphere.

[0047] Preferably, the protective atmosphere comprises nitrogen or argon.

[0048] As a preferred technical solution of the present invention, the preparation method comprises:

[0049] (1) dissolving a platinum precursor, a transition metal precursor and a free radical quencher precursor in a solvent at a molar ratio of 1:(0.1-1):(0.01-0.1), adding a base to form a mixed solution, then adding a carbon material to the mixed solution, and performing shear emulsification at a speed of 8000-13000 rpm / min for 0.5-6 h to obtain a reaction slurry, wherein the concentration of the carbon material in the solvent is 0.5-10 mg / mL;

[0050] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 130 to 190° C. for 2 to 60 minutes, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0051] (3) Under a protective atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 500 to 1200° C. for 0.5 to 12 h to obtain the platinum-based multi-metal catalyst.

[0052] In a second aspect, the present invention provides a platinum-based multi-metal catalyst, which is prepared by the preparation method described in the first aspect.

[0053] As a preferred technical solution of the present invention, the platinum-based multi-metal catalyst includes a carbon carrier, platinum transition metal alloy particles and free radical quencher particles, and the platinum transition metal alloy particles and free radical quencher particles are both loaded on the carbon carrier.

[0054] The free radical quencher particles in the present invention include cerium oxide particles or manganese dioxide particles.

[0055] Preferably, based on the mass fraction of the platinum-based multi-metal catalyst of 100wt%, the mass fraction of the platinum transition metal alloy particles is 10 to 80wt%, for example, it can be 10wt%, 10wt%, 10wt%, 10wt%, 10wt%, 10wt%, 10wt%, 10wt%, or 10wt%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are equally applicable.

[0056] In a third aspect, the present invention provides a use of the platinum-based multi-metal catalyst described in the second aspect, wherein the platinum-based multi-metal catalyst is used in a proton exchange membrane fuel cell.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] The platinum-based multi-metal catalyst obtained by the preparation method provided by the present invention can achieve the technical effect of improving the oxygen reduction activity of the catalyst, reducing the production cost of the catalyst, and improving the durability of the fuel cell through the interaction between the platinum transition metal alloy particles and the free radical quencher particles. DETAILED DESCRIPTION

[0059] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0060] Example 1

[0061] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0062] (1) 1 mmol of chloroplatinic acid, 0.5 mmol of cobalt chloride, 0.05 mmol of cerium nitrate and 0.5 mmol of potassium hydroxide were dissolved in 50 mL of ethylene glycol to form a mixed solution, and then 223 mg of Ketjen Black EC-600J activated carbon powder was added to the mixed solution, and shear emulsification was performed at a speed of 10000 rpm / min for 2 h to obtain a reaction slurry, wherein the concentration of Ketjen Black EC-600J activated carbon powder in ethylene glycol was 4.46 mg / mL;

[0063] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 150° C. for 10 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0064] (3) Under an argon atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 800° C. for 5 hours to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-cobalt alloy particles in the platinum-based multi-metal catalyst is about 50wt%.

[0065] Example 2

[0066] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0067] (1) 1 mmol of sodium chloroplatinate, 0.1 mmol of ferric nitrate, 0.01 mmol of cerium nitrate and 1.8 mmol of sodium hydroxide were dissolved in 180 mL of isopropanol to form a mixed solution, and then 1800 mg of XC-72R activated carbon powder was added to the mixed solution, and shear emulsification was performed at a speed of 8000 rpm / min for 6 h to obtain a reaction slurry, wherein the concentration of XC-72R activated carbon powder in isopropanol was 10 mg / mL;

[0068] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 130° C. for 60 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0069] (3) Under a nitrogen atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 500° C. for 12 hours to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-iron alloy particles in the platinum-based multi-metal catalyst is about 10wt%.

[0070] Example 3

[0071] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0072] (1) 1 mmol potassium chloroplatinate, 1 mmol nickel acetylacetonate, 0.1 mmol manganese chloride and 1.27 mmol potassium hydroxide were dissolved in 127 mL ethanol to form a mixed solution, and then 63.5 mg Ketjen Black EC-300J activated carbon powder was added to the mixed solution, and shear emulsification was performed at a speed of 13000 rpm / min for 0.5 h to obtain a reaction slurry, wherein the concentration of Ketjen Black EC-300J activated carbon powder in ethanol was 0.5 mg / mL;

[0073] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 190° C. for 2 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0074] (3) Under an argon atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 1200° C. for 0.5 h to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-nickel alloy particles in the platinum-based multi-metal catalyst is about 80 wt %.

[0075] Example 4

[0076] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0077] (1) 1 mmol of ammonium chloroplatinate, 0.5 mmol of copper sulfate, 0.05 mmol of cerium nitrate and 0.5 mmol of potassium hydroxide were dissolved in 50 mL of ethanol to form a mixed solution, and then 223 mg of carbon nanotube powder was added to the mixed solution, and shear emulsification was performed at a speed of 10000 rpm / min for 2 h to obtain a reaction slurry, wherein the concentration of the carbon nanotube powder in ethanol was 4.46 mg / mL;

[0078] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 150° C. for 10 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0079] (3) Under an argon atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 800° C. for 5 hours to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-copper alloy particles in the platinum-based multi-metal catalyst is approximately 48wt%.

[0080] Example 5

[0081] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0082] (1) dissolving 1 mmol of sodium chloroplatinite, 0.5 mmol of cobalt chloride, 0.05 mmol of cerium nitrate and 0.5 mmol of potassium hydroxide in 50 mL of ethylene glycol to form a mixed solution, then adding 223 mg of carbon nanotube powder to the mixed solution, and performing shear emulsification at a speed of 10000 rpm / min for 2 h to obtain a reaction slurry, wherein the concentration of the carbon nanotube powder in the ethylene glycol is 4.46 mg / mL;

[0083] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 150° C. for 10 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0084] (3) Under an argon atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 800° C. for 5 hours to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-cobalt alloy particles in the platinum-based multi-metal catalyst is about 50wt%.

[0085] Example 6

[0086] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0087] (1) 1 mmol potassium chloroplatinite, 0.5 mmol cobalt chloride, 0.05 mmol cerium nitrate and 0.5 mmol potassium hydroxide were dissolved in 50 mL ethylene glycol to form a mixed solution, and then 223 mg of nano-graphite powder was added to the mixed solution, and shear emulsification was performed at a speed of 10000 rpm / min for 2 h to obtain a reaction slurry, wherein the concentration of the nano-graphite powder in the ethylene glycol was 4.46 mg / mL;

[0088] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 150° C. for 10 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0089] (3) Under an argon atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 800° C. for 5 hours to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-cobalt alloy particles in the platinum-based multi-metal catalyst is about 50wt%.

[0090] Example 7

[0091] This embodiment provides a method for preparing a platinum-based multi-metal catalyst, the preparation method comprising:

[0092] (1) dissolving 1 mmol of platinum acetylacetonate, 0.5 mmol of cobalt chloride, 0.05 mmol of cerium nitrate and 0.5 mmol of potassium hydroxide in 50 mL of ethylene glycol to form a mixed solution, then adding 223 mg of graphene powder to the mixed solution, and performing shear emulsification at a speed of 10000 rpm / min for 2 h to obtain a reaction slurry, wherein the concentration of graphene powder in ethylene glycol is 4.46 mg / mL;

[0093] (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 150° C. for 10 min, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor;

[0094] (3) Under an argon atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 800° C. for 5 hours to obtain the platinum-based multi-metal catalyst, wherein the mass fraction of the platinum-cobalt alloy particles in the platinum-based multi-metal catalyst is about 50wt%.

[0095] Example 8

[0096] The difference between this embodiment and embodiment 1 is that the amount of cobalt chloride added in step (1) is 0.05 mmol, and the other process parameters and operating steps are the same as those in embodiment 1.

[0097] Example 9

[0098] The difference between this embodiment and embodiment 1 is that the amount of cobalt chloride added in step (1) is 1.5 mmol, and the other process parameters and operating steps are the same as those in embodiment 1.

[0099] Example 10

[0100] The difference between this embodiment and embodiment 1 is that the amount of cerium nitrate added in step (1) is 0.005 mmol, and the other process parameters and operation steps are the same as those in embodiment 1.

[0101] Embodiment 11

[0102] The difference between this embodiment and embodiment 1 is that the amount of cerium nitrate added in step (1) is 0.15 mmol, and the other process parameters and operation steps are the same as those in embodiment 1.

[0103] Example 12

[0104] The difference between this embodiment and embodiment 1 is that the conductivity of the filtrate in step (2) is 20 μS / cm, and the other process parameters and operation steps are the same as those in embodiment 1.

[0105] Comparative Example 1

[0106] This comparative example provides a commercial catalyst, which is a commercial 50% Pt / C catalyst produced by Tanaka Company of Japan.

[0107] Comparative Example 2

[0108] The difference between this comparative example and Example 1 is that the cobalt chloride and cerium nitrate in step (1) are omitted, and the remaining process parameters and operating steps are the same as those in Example 1.

[0109] Comparative Example 3

[0110] The difference between this comparative example and Example 1 is that cerium nitrate in step (1) is omitted, and the remaining process parameters and operating steps are the same as those in Example 1.

[0111] Comparative Example 4

[0112] The difference between this comparative example and Example 1 is that in step (2), conventional hydrothermal heating is used instead of microwave irradiation heating, and the remaining process parameters and operating steps are the same as those in Example 1.

[0113] The catalysts provided in Examples 1-12 and Comparative Examples 1-4 were mixed with ionomers and a water-alcohol solution to prepare a catalyst slurry, which was then sprayed on both sides of a proton exchange membrane to obtain a fuel cell membrane electrode. The initial output voltage and voltage decay after 200 hours were tested. The results are shown in Table 1.

[0114] Table 1

[0115]

[0116]

[0117] From the data in Table 1, we can get:

[0118] (1) The platinum-based multi-metal catalysts provided in Examples 1-7 were prepared into fuel cell membrane electrodes, and their open circuit potentials were all maintained above 942 mV, and the attenuation after 200 h was all below 45 mV, showing high performance and durability. This indicates that the platinum-based multi-metal catalyst obtained by the preparation method provided by the present invention can improve the oxygen reduction activity of the catalyst, reduce the production cost of the catalyst, and improve the durability of the fuel cell through the interaction between the platinum transition metal alloy particles and the free radical quencher particles.

[0119] (2) The fuel cell membrane electrode prepared by the platinum-based multi-metal catalyst provided in Example 8 has an open circuit potential lower than that of Example 1, and the pressure drop after 200 hours is basically the same as that of Example 1, indicating that the catalyst activity in Example 8 is poor, while the durability of the fuel cell is good. This is because the amount of transition metal precursor added in Example 8 is too low, and the platinum transition metal alloy particles formed are relatively small, which is not conducive to improving the catalyst activity, and has no obvious effect on reducing the amount of platinum. The fuel cell membrane electrode prepared by the platinum-based multi-metal catalyst provided in Example 9 has an open circuit potential that is not much different from that of Example 1, while the pressure drop after 200 hours is higher than that of Example 1, indicating that the catalyst activity in Example 9 is good, while the durability of the fuel cell is poor. This is because the amount of transition metal precursor added in Example 9 is too much, resulting in poor chemical stability of the catalyst and a short life.

[0120] (3) The open circuit potential of the fuel cell membrane electrode prepared by the platinum-based multi-metal catalyst provided in Example 10 is slightly lower than that of Example 1, and the pressure drop after 200 hours is higher than that of Example 1; the open circuit potential of the fuel cell membrane electrode prepared by the platinum-based multi-metal catalyst provided in Example 11 is lower than that of Example 1, and the pressure drop after 200 hours is basically the same as that of Example 1; this is because the amount of free radical quencher precursor added in Example 10 is too low, and the amount of free radical quencher precursor added in Example 11 is too high. The addition of the free radical quencher will sacrifice the performance of the catalyst to a certain extent to improve the life of the proton exchange membrane. Therefore, if the amount added is too low or too high, it is impossible to achieve the effect of taking into account both the performance of the catalyst and the performance of the proton exchange membrane.

[0121] (4) The open circuit potential of the fuel cell membrane electrode prepared by the platinum-based multi-metal catalyst provided in Example 12 is lower than that of Example 1. This is because when preparing the catalyst precursor in Example 12, the conductivity of the filtrate is too large, which causes the ions in the metal precursors such as chloride ions, nitrate ions, and sulfate ions to be adsorbed on the active sites of the catalyst, shielding the catalytic activity.

[0122] (5) Comparative Example 1 provides a commercial catalyst and a fuel cell membrane electrode prepared therefrom, and its catalyst activity and fuel cell stability are both lower than those of Example 1; Compared with Example 1, Comparative Example 2 does not add transition metal precursors and free radical quencher precursors, and its open circuit voltage is low and decays significantly after 200 hours; Compared with Example 1, Comparative Example 3 does not add free radical quencher precursors, and its open circuit voltage decays significantly after 200 hours; Compared with Example 1, Comparative Example 4 adopts the traditional hydrothermal method, and its open circuit voltage level is lower, indicating that the catalyst activity prepared by the traditional hydrothermal method is lower; This illustrates that the platinum-based multi-metal catalyst obtained by the preparation method provided by the present invention can improve the oxygen reduction activity of the catalyst, reduce the production cost of the catalyst, and at the same time improve the durability of the fuel cell, thereby achieving the effect of taking into account both the performance of the catalyst and the durability of the fuel cell.

[0123] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a platinum-based multi-metal catalyst, characterized in that: The preparation method comprises: A platinum precursor, a transition metal precursor, a free radical quencher precursor and a carbon material are dissolved in a solvent to form a reaction slurry, the reaction slurry is subjected to a reduction reaction under microwave irradiation to obtain a catalyst precursor, and then the catalyst precursor is subjected to an alloying treatment to obtain the platinum-based multi-metal catalyst; The molar ratio of the platinum precursor, the transition metal precursor and the free radical quencher precursor is 1:(0.1-1):(0.01-0.05); The temperature of the alloying treatment is 500-1200°C; The alloying treatment time is 0.5 to 12 hours.

2. The preparation method according to claim 1, characterized in that: The preparation process of the reaction slurry comprises: The platinum precursor, the transition metal precursor and the free radical quencher precursor are dissolved in a solvent to form a mixed solution, and then the carbon material is added to the mixed solution for shear emulsification to obtain the reaction slurry.

3. The preparation method according to claim 2, characterized in that: A base is also added to the mixed solution.

4. The preparation method according to claim 3, characterized in that: The base includes sodium hydroxide and / or potassium hydroxide.

5. The preparation method according to claim 1, characterized in that: The platinum precursor includes any one of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, ammonium chloroplatinate, potassium chloroplatinite, sodium chloroplatinite or platinum acetylacetonate, or a combination of at least two thereof.

6. The preparation method according to claim 1, characterized in that: The transition metal precursor includes any one of nitrates, sulfates, acetylacetonates or chlorides of transition metals, or a combination of at least two of them.

7. The preparation method according to claim 1, characterized in that: The transition metal in the transition metal precursor includes any one of cobalt, nickel, iron or copper.

8. The preparation method according to claim 1, characterized in that: The free radical quencher precursor includes any one of cerium nitrate, manganese nitrate, cerium chloride or manganese chloride.

9. The preparation method according to claim 1, characterized in that: The solvent includes any one of ethanol, ethylene glycol or isopropanol, or a combination of at least two of them.

10. The preparation method according to claim 1, characterized in that: The carbon material includes an activated carbon material.

11. The preparation method according to claim 10, characterized in that: The activated carbon material includes any one of XC-72R, Ketjen Black EC-300J, Ketjen Black EC-600J, carbon nanotubes, nano graphite powder, and graphene, or a combination of at least two thereof.

12. The preparation method according to claim 1, characterized in that: The concentration of the carbon material in the solvent is 0.5-10 mg / mL.

13. The preparation method according to claim 2, characterized in that: The rotation speed of the shear emulsification is 8000-13000 rpm / min.

14. The preparation method according to claim 2, characterized in that: The shear emulsification time is 0.5 to 6 hours.

15. The preparation method according to claim 1, characterized in that: The pH of the reaction slurry is 10-13.

16. The preparation method according to claim 1, characterized in that: The temperature of the microwave irradiation is 130-190°C.

17. The preparation method according to claim 1, characterized in that: The microwave irradiation time is 2 to 60 minutes.

18. The preparation method according to claim 1, characterized in that: After the microwave irradiation, filtering, washing and vacuum drying are performed in sequence to obtain the catalyst precursor.

19. The preparation method according to claim 18, characterized in that: The end point of the filtration and washing is that the conductivity of the filtrate is ≤5 μS / cm.

20. The preparation method according to claim 1, characterized in that: The alloying treatment is carried out under a protective atmosphere.

21. The preparation method according to claim 20, characterized in that: The protective atmosphere includes nitrogen or argon.

22. The preparation method according to claim 1, characterized in that: The preparation method comprises: (1) dissolving a platinum precursor, a transition metal precursor and a free radical quencher precursor in a solvent at a molar ratio of 1:(0.1-1):(0.01-0.05), adding a base to form a mixed solution, then adding a carbon material to the mixed solution, and performing shear emulsification at a speed of 8000-13000 rpm / min for 0.5-6 h to obtain a reaction slurry, wherein the concentration of the carbon material in the solvent is 0.5-10 mg / mL; (2) subjecting the reaction slurry obtained in step (1) to a reduction reaction at a microwave irradiation temperature of 130 to 190° C. for 2 to 60 minutes, followed by filtering and washing until the conductivity of the filtrate is ≤5 μS / cm, and then vacuum drying to obtain a catalyst precursor; (3) Under a protective atmosphere, the catalyst precursor obtained in step (2) is subjected to an alloying treatment at a temperature of 500 to 1200° C. for 0.5 to 12 h to obtain the platinum-based multi-metal catalyst.

23. A platinum-based multi-metal catalyst for a proton exchange membrane fuel cell, characterized in that: The platinum-based multi-metal catalyst is prepared by the preparation method described in any one of claims 1-22.

24. The platinum-based multi-metal catalyst according to claim 23, characterized in that The platinum-based multi-metal catalyst comprises a carbon carrier, platinum transition metal alloy particles and free radical quencher particles, wherein the platinum transition metal alloy particles and the free radical quencher particles are both loaded on the carbon carrier.

25. The platinum-based multi-metal catalyst according to claim 24, characterized in that Based on 100wt% of the mass fraction of the platinum-based multi-metal catalyst, the mass fraction of the platinum transition metal alloy particles is 10-80wt%.

26. Use of the platinum-based multi-metal catalyst according to any one of claims 23 to 25, characterized in that: The platinum-based multi-metal catalyst is used in proton exchange membrane fuel cells.

Images