Method for preparing metal catalyst and metal catalyst for fuel cell

Abstract

The application provides a preparation method of a metal catalyst and the metal catalyst and a fuel cell. The preparation method of the metal catalyst comprises the following steps: dispersing and immersing carrier particles in a metal precursor solution to obtain a solid-liquid mixed system A; performing shearing dispersion treatment on the solid-liquid mixed system A by using a shearing dispersion machine equipped with a corrosion-resistant material cutter head to obtain viscous slurry B; performing drying treatment on the viscous slurry B to obtain carrier particles C loaded with the metal precursor; and performing reduction treatment on the carrier particles C loaded with the metal precursor in a reducing atmosphere and / or performing heat treatment on the carrier particles C loaded with the metal precursor in an inert atmosphere to obtain the metal catalyst. The shearing dispersion treatment improves the dispersibility and wettability of the carrier particles, enables the metal precursor salt to be uniformly adsorbed and precipitated on the surface of the carrier particles, and increases the metal loading in the metal catalyst, thereby improving the stability of the metal in the carrier particles.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and more particularly to a preparation method of a metal catalyst and the metal catalyst and a fuel cell. BACKGROUND

[0002] A fuel cell is a clean and efficient energy conversion device. Compared with traditional primary or secondary batteries, a fuel cell has higher energy density and faster charging speed. Compared with a traditional heat engine, the energy conversion rate of a fuel cell is much higher than that of a traditional heat engine. Moreover, in a fuel cell, fuel is directly converted into clean combustion products, such as water and carbon dioxide, and almost no sulfur compounds and nitrogen oxides are emitted, so it is a clean energy source.

[0003] Catalyst materials are key materials for fuel cells. Among them, platinum-based catalysts are widely considered to be the most important anode catalysts in direct fuel cells due to their excellent electronic properties. Although platinum-based catalysts have excellent catalytic effects, they also have problems such as poor electrocatalytic stability and high cost. One of the fundamental ways to improve the utilization rate of platinum in the catalyst, enhance the stability and anti-poisoning ability of the catalyst, and reduce the cost of the fuel cell is to increase the utilization rate of platinum in the catalyst.

[0004] To improve the utilization rate of Pt, Pt is usually supported on a carbon support material to improve the dispersion of Pt. Meanwhile, the pore structure existing on the carbon support and carbon agglomerates can effectively improve the mass transfer of reactants and products in the catalyst layer of a fuel cell, thereby improving the performance of the fuel cell. In order to reduce the thickness of the catalyst layer and reduce the mass transfer resistance, a fuel cell generally uses a carbon-supported catalyst with a high metal loading (more than 40 wt%).

[0005] The commonly used method for preparing a carbon-supported metal catalyst is impregnation. The basic principle of traditional impregnation is to use the adsorption of the support to adsorb metal precursors on the support. Specifically, the support is dispersed in a liquid or gas containing metal precursors, the support adsorbs a full monolayer (or not a full monolayer) of metal precursors to reach impregnation equilibrium, and then the liquid or gas is removed, followed by drying, calcination, activation, etc.

[0006] Traditional impregnation has been successfully applied in the preparation of automobile exhaust three-way catalysts or petroleum gas conversion catalysts, etc. This impregnation method is mainly suitable for preparing catalysts with a low loading (<5%). When a high-loading (40%-80%) fuel cell catalyst is prepared by traditional impregnation, two problems are faced:

[0007] First, due to the low loading of the metal catalyst, the surface of the carbon support cannot carry a sufficient amount of metal precursors by equilibrium adsorption. The specific surface area of the carbon support is about 270 m 2XC-72R carbon black with a specific surface area of 800 m2 / g, after adsorbing full monolayer of chloroplatinic acid molecules, the Pt loading is about 8wt%. Even if the specific surface area of Ketjenblack EC-300J is about 800 m2 / g, the Pt loading corresponding to full monolayer of chloroplatinic acid molecules is only about 26wt%. If the loading is to reach 40%-80%, the mesopore of the carrier needs to be completely filled with the precursor solution, and the mesopore volume needs to reach the requirement, for example, about 0.44 ml / g for XC-72R and about 0.98 ml / g for KJ-300, and the solution concentration needs to be extremely high to meet the requirement. 2 If the loading is to reach 40%-80%, the mesopore of the carrier needs to be completely filled with the precursor solution, and the mesopore volume needs to reach the requirement, for example, about 0.44 ml / g for XC-72R and about 0.98 ml / g for KJ-300, and the solution concentration needs to be extremely high to meet the requirement.

[0008] Secondly, because the fuel cell carrier generally has a high graphitization degree, the surface is in a hydrophobic state, and the wettability between the carrier and the metal precursor solution is poor, which hinders the metal precursor solution from entering the pore structure of the carbon carrier particles and carbon agglomerates in the impregnation process, so that the metal precursor salt cannot be uniformly adsorbed and precipitated on the surface of the carbon carrier.

[0009] These problems result in that the carbon-supported metal catalyst prepared by the traditional impregnation method has low stability. SUMMARY

[0010] Therefore, an object of the present application is to provide a preparation method of a metal catalyst to solve the technical problems in the prior art that the loading of the metal catalyst in the carbon-supported metal catalyst prepared by the traditional impregnation method is low, the metal precursor salt cannot be uniformly adsorbed and precipitated on the surface of the carbon carrier, and the stability of the carbon-supported metal catalyst is low. Unlike general magnetic stirring or mechanical stirring, the solid-liquid mixed system is subjected to high-speed stirring, grinding and shearing by a special cutter head of a high-speed dispersion machine to achieve uniform mixing and enhance the wettability of the carbon carrier to water. Thus, the above problems are solved.

[0011] Another object of the present application is to provide a metal catalyst.

[0012] Still another object of the present application is to provide a fuel cell.

[0013] To achieve the above objects, the technical scheme adopted by the present application is as follows:

[0014] A preparation method of a metal catalyst, comprising the following steps:

[0015] dispersing and immersing the carrier particles in the metal precursor solution to obtain a solid-liquid mixed system A;

[0016] subjecting the solid-liquid mixed system A to shearing and dispersion treatment by a shearing and dispersion machine equipped with a corrosion-resistant cutter head to obtain a viscous slurry B;

[0017] drying the viscous slurry B to obtain carrier particles C loaded with the metal precursor.

[0018] The carrier particles C loaded with the metal precursor are placed in a reducing atmosphere for reduction treatment and / or in an inert atmosphere for heat treatment, to obtain a metal catalyst.

[0019] Optionally, the metal elements in the metal precursor solution include at least one of platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese; and / or,

[0020] The metal precursor solution is an aqueous solution of a water-soluble metal salt or a water-soluble complex or a water-soluble alloy salt containing at least one of platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese.

[0021] Optionally, the concentration of the metal precursor solution is 0.05-0.32 mol / L, and the volume of the metal precursor solution is 1.5-10 times the tap volume of the carrier particles; and / or,

[0022] The metal loading of the metal catalyst is 40-80 wt%.

[0023] Optionally, the carrier particles include at least one of a pure carbon carrier, a metal-doped carbon carrier, and a non-metal atom-doped carbon carrier; and / or,

[0024] The carrier particles include at least one of acetylene black, activated carbon, carbon nanotubes, and graphene.

[0025] Optionally, the rotational speed of the shear dispersion treatment is 1200-15000 rpm, and the heating temperature is 50-90°C; and / or,

[0026] The solid-liquid mixture A is also subjected to ultrasonic treatment before the shear dispersion treatment, and the shear dispersion treatment is performed under heating.

[0027] Optionally, the ultrasonic treatment and the shear dispersion treatment are repeatedly operated alternately for multiple times until a viscous slurry B without clear water is obtained; and / or,

[0028] The viscous slurry B includes the following components in mass percentage: water 70-85%, metal precursor 13-15%, and carrier particles 6-8%.

[0029] Optionally, the gas of the reducing atmosphere includes at least one of hydrogen, carbon monoxide, and ammonia; and / or,

[0030] The temperature of the reduction treatment is 60-800°C.

[0031] Optionally, the gas of the inert atmosphere includes argon or nitrogen; and / or,

[0032] The temperature of the heat treatment is 60-800°C.

[0033] and a metal catalyst prepared by the preparation method of the metal catalyst.

[0034] and a fuel cell comprising the metal catalyst.

[0035] 1. The preparation method of the metal catalyst provided by the present application, the carrier particles are first dispersed and immersed in a metal precursor solution to produce a preliminary natural adsorption, part of the metal precursor solution is naturally adsorbed on the surface of the carrier particles to obtain a solid-liquid mixed system A; the solid-liquid mixed system A is treated by using a shearing disperser, under the mechanical action force of high-speed shearing dispersion treatment, the dispersibility of the carrier particles and the metal precursor solution is improved, and the wettability of the carrier particles is improved, so that the metal precursor solution can be uniformly adsorbed on the surface of the carrier particles; all the water is removed by drying treatment, and the metal precursor is precipitated and attached to the surface of the carrier particles; the anion part in the metal precursor is removed by reduction treatment and / or heat treatment, so that the metal cation is reduced to obtain the metal catalyst; compared with the prior art, the preparation method of the metal catalyst of the present application uses shearing dispersion treatment to improve the dispersibility and wettability of the carrier particles, so that the metal precursor salt can be uniformly adsorbed and precipitated on the surface of the carrier particles, and the metal loading in the metal catalyst is increased, thereby improving the stability of the metal in the carrier particles, i.e. improving the catalytic performance and stability of the metal catalyst;

[0036] 2. The metal catalyst provided by the present application has high metal loading, the metal is uniformly loaded on the surface of the carrier particles, and the stability of the metal catalyst is improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] The present application will be further described below in combination with the drawings and examples, and the drawings are as follows:

[0038] Figure 1 It is a transmission electron microscope (TEM) image of the metal catalyst of Example 1 of the present application;

[0039] Figure 2 It is a transmission electron microscope (TEM) image of the metal catalyst of Example 2 of the present application;

[0040] Figure 3 It is a half-wave potential comparison diagram of the oxygen reduction linear scan curves of the metal catalysts of Example 1 and Comparative Example 1 of the present application;

[0041] Figure 4 It is a comparison diagram of the cyclic voltammetry curves of the metal catalysts of Example 1 and Comparative Example 1 of the present application;

[0042] Figure 5 It is a half-wave potential comparison diagram of the oxygen reduction linear scan curves of the metal catalysts of Example 1 and Example 4 of the present application;

[0043] Figure 6 Figure 1 is a cyclic voltammetry curve of a metal catalyst according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, and not to limit the present application.

[0045] The method for preparing a metal catalyst according to an embodiment of the present application comprises the following steps:

[0046] S10: dispersing and immersing the carrier particles in the metal precursor solution to obtain a solid-liquid mixed system A.

[0047] The carrier particles are dispersed and immersed in the metal precursor solution to produce a preliminary natural adsorption, and part of the metal precursor solution is naturally adsorbed on the surface of the carrier particles to obtain a solid-liquid mixed system A.

[0048] The main role of the metal precursor solution is to introduce the target metal element in the form of a solution, which is adsorbed on the surface of the carrier particles through the permeability and wettability of the solution, and then the other components in the solution except the target metal element are removed, so that the target metal element is loaded on the carrier particles.

[0049] Optionally, the metal elements in the metal precursor solution include at least one of platinum, palladium, iridium, gold, iron, cobalt, nickel, copper and manganese, i.e., the selected metal element is the target catalytic metal. In implementation, it can be a single metal element, such as only platinum, palladium, iridium, gold, iron, cobalt, nickel, copper or manganese, or an alloy, such as platinum-nickel alloy, platinum-cobalt alloy, platinum-copper alloy, palladium-nickel alloy, palladium-cobalt alloy or palladium-copper alloy, etc., and the appropriate metal element can be selected as needed.

[0050] Optionally, the metal precursor solution is an aqueous metal salt solution or an aqueous complex solution or an aqueous alloy salt solution including at least one of platinum, palladium, iridium, gold, iron, cobalt, nickel, copper and manganese. It can be understood that the aqueous metal salt is a salt corresponding to the metal element, the aqueous complex is a complex corresponding to the metal element, and the aqueous alloy salt is a salt of an alloy of at least two metal elements.

[0051] In some embodiments, the concentration of the metal precursor solution is 0.05-0.32 mol / L, and the volume of the metal precursor solution is 1.5-10 times the tap density volume of the carrier particles. If the volume of the metal precursor solution is too small, for example, the ratio of the volume of the metal precursor solution to the volume of the carrier particles is less than 1.5 times, the carrier particles can not be completely immersed in the metal precursor solution, or the solid content of the solid-liquid mixture A is too high, which is not easy to disperse, and can easily cause agglomeration. If the volume of the metal precursor solution is too large, for example, the ratio of the volume of the metal precursor solution to the volume of the carrier particles is greater than 10 times, the solid content of the solid-liquid mixture A is too low, that is, the concentration is too dilute, although the dispersibility is good, but it will increase the difficulty of subsequent ultrasonic treatment and shear dispersion treatment, and heating and evaporating water will take a long time, which reduces the processing efficiency and does not meet the economic benefits.

[0052] Therefore, in practice, the volume of the metal precursor solution can be selected to be 1.5-10 times the volume of the carrier particles. Under this volume ratio, the carrier particles can be completely immersed in the metal precursor solution, and the solid content of the solid-liquid mixture A is moderate, the adsorption space of the carrier particles matches the content of the metal precursor, avoiding the problem of material waste caused by excessive metal precursor, and the efficiency of ultrasonic treatment and shear dispersion treatment is higher.

[0053] Optionally, the carrier particles include at least one of pure carbon carriers, metal-doped carbon carriers, and non-metal atom-doped carbon carriers. These carriers are all carbon carriers, have a porous structure, a large specific surface area, can increase the loading area, and have mechanical properties and electrical properties that meet the requirements of being a carrier of the catalytic metal of the fuel cell.

[0054] Optionally, the carrier particles include at least one of acetylene black, activated carbon, carbon nanotubes, and graphene. Acetylene black, activated carbon, carbon nanotubes, and graphene are all carbon carriers, have a three-dimensional through ordered pore structure, a large specific surface area, and can provide a large adsorption space, which is beneficial to increasing the metal loading.

[0055] S20: The solid-liquid mixture A is subjected to shear dispersion treatment by a shear dispersion machine equipped with a corrosion-resistant cutter head to obtain a viscous slurry B.

[0056] Through shear dispersion treatment, the dispersibility of the carrier particles and the metal precursor solution, and the wettability of the carrier particles are further improved under the mechanical action of shear dispersion treatment. If the carrier particles have a porous structure, the metal precursor solution can be promoted to enter the pore structure of the carrier particles, so that the metal precursor solution can be uniformly adsorbed on the surface of the carrier particles.

[0057] The shearing dispersion treatment is generally performed by a high-shear dispersion machine. Unlike general magnetic stirring or mechanical stirring, the solid-liquid mixture A is subjected to high-speed stirring, grinding and shearing by the high-speed rotating cutter head of the high-shear dispersion machine, so as to achieve uniform mixing and enhance the wettability of the carbon carrier to water. During the shearing dispersion treatment, the centrifugal force generated by the high-speed rotation of the high-shear dispersion machine sucks the solid-liquid mixture A into the cutter head, crushes and mixes it inside the cutter head, and then throws it out, further dispersing the carrier particles, avoiding agglomeration of the carrier particles, and under the action of the centrifugal force of the shearing dispersion, the metal precursor solution enters the pore structure of the carrier particles, increasing the contact area between the metal precursor solution and the carrier particles.

[0058] Optionally, the corrosion-resistant material cutter head is made of plastic, ceramic, titanium, titanium alloy or tungsten carbide, etc. These materials have excellent acid and alkali corrosion resistance, avoiding damage to the cutter head during high-speed stirring, grinding and shearing of the solid-liquid mixture A.

[0059] Optionally, the shearing dispersion treatment has a shearing dispersion speed of 1200 rpm-15000 rpm, which provides sufficient centrifugal force to disperse the carrier particles and promotes the metal precursor solution to enter the pore structure of the carrier particles. The shearing dispersion treatment has a heating temperature of 50°C-90°C, which slowly evaporates water, so that the metal precursor solution can uniformly adhere to the surface of the carrier particles, avoiding high temperature and fast evaporation speed, which may cause rapid shrinkage of the metal precursor solution and uneven adhesion.

[0060] Optionally, the solid-liquid mixture A is also subjected to ultrasonic treatment before the shearing dispersion treatment, and the shearing dispersion treatment is performed under heating conditions.

[0061] The ultrasonic treatment improves the dispersibility of the solid-liquid mixture A and promotes the metal precursor solution to enter the pore structure of the carrier particles, and then the shearing dispersion treatment is performed under heating conditions. Under the mechanical action of the shearing dispersion treatment, the dispersibility of the carrier particles and the metal precursor solution is further improved. Evaporating water during the shearing dispersion treatment can increase the concentration of the metal precursor adsorbed on the surface of the carrier particles and facilitate the subsequent drying and separation.

[0062] In some embodiments, the solid-liquid mixture A has a high water content, and the ultrasonic treatment and the shearing dispersion treatment cannot completely evaporate the clear water. In this case, the ultrasonic treatment and the shearing dispersion treatment can be repeatedly operated alternately, for example, ultrasonic treatment-shearing dispersion treatment-ultrasonic treatment-shearing dispersion treatment-ultrasonic treatment-shearing dispersion treatment-, and so on. This cycle is repeated alternately until the viscous slurry B without clear water is obtained. On the one hand, water is evaporated, and on the other hand, the metal precursor solution in the carrier particles is increased by the repeated operation of the ultrasonic treatment and the shearing dispersion treatment.

[0063] The visible water in the embodiments of the present application refers to water that can be seen, i.e., the thick slurry B has no visible water. The water in the thick slurry B is inside the thick slurry B and is not visible water.

[0064] It can be understood that the time of ultrasonic treatment can be selected according to the dispersion of the solid-liquid mixed system A to control the dispersion of the system and the operation efficiency. According to experiments, the time of ultrasonic treatment can be selected to be 1-60 min.

[0065] It can be understood that the time of shear dispersion treatment can be selected according to the dispersion of the carrier particles and the adsorption of the metal precursor solution to obtain a good metal loading effect. According to experiments, the time of shear dispersion treatment can be selected to be 1-60 min.

[0066] The thick slurry B includes the following components with mass percentage: water 70%-85%, metal precursor 13%-15%, and carrier particles 6%-8%. The water completely wraps the carrier particles and sufficiently infiltrates the carrier particles, so that the metal precursor can be uniformly adsorbed on the surface of the carrier particles, and the proportion of the metal precursor and the carrier particles is matched, which provides a basis for improving the metal loading.

[0067] S30: The thick slurry B is subjected to drying treatment to obtain carrier particles C loaded with the metal precursor.

[0068] The drying treatment removes all the water, so that the metal precursor is precipitated and attached to the surface of the carrier particles. At this time, the metal salt or the metal complex or the alloy salt is attached to the surface of the carrier particles.

[0069] The method of drying treatment can be freeze drying or heating drying.

[0070] In some embodiments, the conditions of freeze drying treatment are selected to be: pressure lower than 10 Pa and temperature lower than -59℃. Under the conditions, the water is quickly frozen and then sublimed, and the metal precursor forms a thin layer and is attached to the surface of the carrier particles.

[0071] In some embodiments, the temperature of heating drying is 90℃-105℃, so that the water is evaporated, and the metal precursor forms a thin layer and is attached to the surface of the carrier particles.

[0072] S40: The carrier particles C loaded with the metal precursor are placed in a reducing atmosphere for reduction treatment and / or in an inert atmosphere for heat treatment to obtain a metal catalyst.

[0073] The reduction treatment and / or the heat treatment remove the anion part in the metal precursor, so that the metal cation is reduced, the target metal is loaded on the surface of the carrier particles, and the metal catalyst is obtained.

[0074] In some embodiments, the anion part of the metal salt or metal complex or alloy salt in the metal precursor is not easy to decompose under heat, and the reaction needs to be carried out in a reducing atmosphere, so that the metal ions are reduced to obtain the metal.

[0075] In some embodiments, the anion part of the metal salt or metal complex or alloy salt in the metal precursor is easy to decompose under heat, and the carrier particles C are subjected to heat treatment in an inert atmosphere to remove the anion part in the metal precursor, so that the metal ions are reduced to obtain the metal, without the need for further reduction treatment in a reducing atmosphere.

[0076] In some embodiments, the metal precursor needs to be subjected to heat treatment in an inert atmosphere and reduction treatment in a reducing atmosphere in combination to completely reduce the metal ions to the target metal state.

[0077] Therefore, the reduction treatment in the reducing atmosphere and the heat treatment in the inert atmosphere can be selected to be carried out in combination or separately according to the type of the metal precursor.

[0078] Optionally, the reducing atmosphere gas includes at least one of hydrogen, carbon monoxide, and ammonia, which has strong reducing property and does not produce other side reactions to interfere with the loading of the target metal.

[0079] In some embodiments, the temperature of the reduction treatment is 60-800°C, which provides sufficient energy to promote the reduction reaction to proceed in the positive direction.

[0080] Optionally, the inert atmosphere gas includes argon or nitrogen, which does not react with the metal and protects the reduced metal from air oxidation, so that the target metal can be successfully reduced.

[0081] In some embodiments, the temperature of the heat treatment can be selected according to the decomposition of the anion, for example, which can be 60-800°C.

[0082] Optionally, the metal loading of the metal catalyst is 40-80wt%.

[0083] The preparation method of the metal catalyst provided in the embodiments of the present application adopts the method of improving the dispersibility and wettability of the carbon carrier in the solid-liquid mixed system A by shearing dispersion, evaporating the excess water, and finally drying and gas-phase reduction, to obtain a high-loading metal catalyst for fuel cells with uniform dispersion, uniform metal particle size, and good catalytic activity.

[0084] Compared with the prior art, the preparation method of the metal catalyst in the embodiment of the application adopts ultrasonic treatment and shearing dispersion treatment in cooperation, improves the dispersibility and wettability of the carrier particles, enables the metal precursor salt to be uniformly adsorbed and precipitated on the surface of the carrier particles, and increases the metal loading in the metal catalyst, thereby improving the stability of the metal in the carrier particles, that is, improving the stability of the metal catalyst.

[0085] The preparation method of the metal catalyst in the embodiment of the application is simple and easy to implement, does not need to add additional surfactants, and is suitable for preparing high-loading (40wt%-80wt%) kilogram-level catalysts in scale-up production. The problems of poor activity and poor durability of the metal catalyst in a long-time use process due to the difficulty in improving the loading of the high-loading catalyst for fuel cells prepared by the impregnation method, the easy agglomeration of particles, and the uneven dispersion are solved.

[0086] The embodiment of the application further provides a metal catalyst, which is prepared by the above preparation method of the metal catalyst, has a high metal loading, and has the metal uniformly loaded on the surface of the carrier particles, thereby improving the stability of the metal catalyst and improving the use stability and electrical performance of the fuel cell when applied to the fuel cell.

[0087] The following is illustrated by multiple embodiments.

[0088] Embodiment 1

[0089] The metal catalyst in the embodiment is a total amount of 3g of 40wt% platinum-carbon catalyst for fuel cells, and the preparation method of the metal catalyst includes the following steps:

[0090] S01: 50ml of a chloroplatinic acid solution (containing 6.15mmol of chloroplatinic acid) is added to a container, and then 1.8g of Ketjenblack EC-300J activated carbon is added to the container, so that the activated carbon particles are completely immersed in the chloroplatinic acid solution, to obtain a solid-liquid mixed system A;

[0091] S02: The solid-liquid mixed system A is subjected to ultrasonic treatment for 30min, and is recorded as a solid-liquid mixed system B;

[0092] S03: The solid-liquid mixed system B is heated to 80℃, and at the same time, a shearing dispersion machine equipped with a titanium metal knife head is used to perform shearing dispersion treatment at a speed of 3000rpm for 30min, and is recorded as a solid-liquid mixed system C;

[0093] S04: The solid-liquid mixed system C is kept at 80℃, and is subjected to shearing dispersion treatment at a speed of 1200rpm for 30min, and is recorded as a solid-liquid mixed system D;

[0094] S05: repeat the ultrasonic treatment-shear dispersion treatment operation for the solid-liquid mixture system D multiple times, each time of ultrasonic treatment is 30 min, each time of shear dispersion treatment is at 80°C, 1200 rpm, 60 min, until a thick slurry B without water is obtained;

[0095] S06: freeze the thick slurry B in a refrigerator for 4 h, then freeze dry in a freeze dryer at a temperature lower than -59°C and a pressure lower than 10 Pa for 24 h, to obtain the activated carbon particles C loaded with metal precursors;

[0096] S07: place the activated carbon particles C loaded with metal precursors in a hydrogen atmosphere, and perform reduction treatment at 120°C for 2 h, the flow rate of hydrogen is 20 ml / min, after cooling, a platinum carbon catalyst with a loading of 40 wt% is obtained.

[0097] Example 2

[0098] The metal catalyst of this example is a 60 wt% platinum carbon catalyst for fuel cells with a total amount of 100 g, and the preparation method of the metal catalyst comprises the following steps:

[0099] S01: add 1000 ml of chloroplatinic acid solution (containing 307.7 mmol of chloroplatinic acid) into a container, then add 40 g of Ketjenblack EC-300J activated carbon into the container, so that the activated carbon particles are completely immersed in the chloroplatinic acid solution, denoted as solid-liquid mixture system A;

[0100] S02: ultrasonic treatment of the solid-liquid mixture system A for 30 min, denoted as solid-liquid mixture system B;

[0101] S03: heat the solid-liquid mixture system B to 80°C, at the same time, use a shear dispersion machine equipped with a tungsten carbide cutter head to shear at a speed of 3000 rpm for 30 min, denoted as solid-liquid mixture system C;

[0102] S04: keep the solid-liquid mixture system C at 80°C, shear at a speed of 1200 rpm for 30 min, denoted as solid-liquid mixture system D;

[0103] S05: repeat the ultrasonic treatment-shear dispersion treatment operation for the solid-liquid mixture system D multiple times, each time of ultrasonic treatment is 30 min, each time of shear dispersion treatment is at 80°C, 1200 rpm, 120 min, until a thick slurry B without water is obtained;

[0104] S06: freeze the thick slurry B in a refrigerator for 4 h, then freeze dry in a freeze dryer at a temperature lower than -59°C and a pressure lower than 10 Pa for 48 h, to obtain the activated carbon particles C loaded with metal precursors;

[0105] S07: The metal precursor-loaded activated carbon particles C were placed in a hydrogen atmosphere, and reduction treatment was performed at a temperature of 120°C for 4h, with a hydrogen flow rate of 200ml / min. After cooling, a platinum carbon catalyst with a loading of 60wt% was obtained.

[0106] Example 3

[0107] The metal catalyst of this example was a 40wt% palladium carbon catalyst for fuel cells with a total amount of 100mg. The preparation method of the metal catalyst included the following steps:

[0108] S01: 5ml of a palladium chloride solution (containing chloroplatinic acid 0.564mmol) was added to a container, and then 90mg of Ketjenblack EC-300J activated carbon was added to the container, so that the activated carbon particles were completely immersed in the palladium chloride solution, and the solid-liquid mixture system A was recorded;

[0109] S02: The solid-liquid mixture system A was subjected to ultrasonic treatment for 30min, and the solid-liquid mixture system B was recorded;

[0110] S03: The solid-liquid mixture system B was heated to 80°C, and at the same time, a shear dispersion machine equipped with a ceramic knife head was used for shear dispersion treatment at a speed of 3000rpm for 30min, and the solid-liquid mixture system C was recorded;

[0111] S04: The solid-liquid mixture system C was kept at 80°C, and shear dispersion treatment was performed at a speed of 1200rpm for 20min, and the solid-liquid mixture system D was recorded;

[0112] S05: The solid-liquid mixture system D was repeatedly subjected to ultrasonic treatment and shear dispersion treatment, each time for 10min, at a temperature of 80°C, a speed of 1200rpm, and a time of 20min, until a viscous slurry B without water was obtained;

[0113] S06: The viscous slurry B was placed in a refrigerator and frozen for 4h, and then freeze-dried in a freeze-drier at a temperature of less than -59°C and a pressure of less than 10Pa for 24h, to obtain the metal precursor-loaded activated carbon particles C;

[0114] S07: The metal precursor-loaded activated carbon particles C were placed in a hydrogen atmosphere, and reduction treatment was performed at a temperature of 120°C for 2h, with a hydrogen flow rate of 10ml / min. After cooling, a palladium carbon catalyst with a loading of 40wt% was obtained.

[0115] Example 4

[0116] The metal catalyst of the present embodiment is a 40wt% platinum copper carbon catalyst for fuel cells with a total amount of 100 mg, and the preparation method of the metal catalyst comprises the following steps:

[0117] S01: 5 ml of a mixed solution of chloroplatinic acid and copper chloride (containing 0.31 mmol of chloroplatinic acid and 0.103 mol of copper chloride) was added to a container, and then 90 mg of Ketjenblack EC-300J activated carbon was added to the container, so that the activated carbon particles were completely immersed in the mixed solution of chloroplatinic acid and copper chloride, and the solid-liquid mixed system A was recorded;

[0118] S02: The solid-liquid mixed system A was subjected to ultrasonic treatment for 30 min, and the solid-liquid mixed system B was recorded;

[0119] S03: The solid-liquid mixed system B was heated to 80°C, and at the same time, a shearing dispersion machine equipped with a plastic knife head was used for shearing dispersion treatment at a speed of 3000 rpm for 30 min, and the solid-liquid mixed system C was recorded;

[0120] S04: The solid-liquid mixed system C was kept at 80°C and sheared and dispersed at a speed of 1200 rpm for 20 min, and the solid-liquid mixed system D was recorded;

[0121] S05: The solid-liquid mixed system D was repeatedly subjected to ultrasonic treatment and shearing dispersion treatment, each time for 10 min, at a temperature of 80°C, a speed of 1200 rpm, and a time of 20 min, until a viscous slurry B without water was obtained;

[0122] S06: The viscous slurry B was placed in a refrigerator and frozen for 4 h, and then freeze-dried in a freeze-drier at a temperature below -59°C and a pressure below 10 Pa for 24 h, to obtain activated carbon particles C loaded with metal precursors;

[0123] S07: The activated carbon particles C loaded with metal precursors were placed in a hydrogen atmosphere and subjected to reduction treatment at a temperature of 300°C for 2 h, with a hydrogen flow rate of 20 ml / min, and then heat-treated in an Ar atmosphere at a temperature of 600°C for 6 h, with an Ar flow rate of 20 ml / min, to obtain a platinum copper carbon catalyst with a loading of 40wt%.

[0124] Comparative Example 1

[0125] The metal catalyst of the present embodiment is a 40wt% platinum copper carbon catalyst for fuel cells with a total amount of 100 mg, and the preparation method of the metal catalyst comprises the following steps:

[0126] S01: 50 ml of chloroplatinic acid solution (containing 6.15 mmol of chloroplatinic acid) was added into a container, and then 1.8 g of Ketjenblack EC-300J activated carbon was added into the container, so that the activated carbon particles were completely immersed in the chloroplatinic acid solution, and the solid-liquid mixed system A was obtained;

[0127] S02: The solid-liquid mixed system A was subjected to ultrasonic treatment for 30 min, and the solid-liquid mixed system B was obtained;

[0128] S03: The solid-liquid mixed system B was subjected to heating evaporation until a viscous slurry C without water was obtained;

[0129] S04: The viscous slurry C was placed in a refrigerator and frozen for 4 h, and then freeze-dried in a freeze dryer at a temperature lower than -59°C and a pressure lower than 10 Pa for 24 h, and the activated carbon particles D loaded with metal precursors were obtained;

[0130] S05: The activated carbon particles D loaded with metal precursors were placed in a hydrogen atmosphere and subjected to reduction treatment at a temperature of 120°C for 2 h, and the flow rate of hydrogen was 20 ml / min. After cooling, the platinum-carbon catalyst with a loading of 40 wt% was obtained.

[0131] The metal catalysts prepared in Example 1 and Comparative Example 1 were subjected to transmission electron microscopy (TEM) test, and the results are shown in Figure 1 and Figure 2 It can be seen from Figure 1 and Figure 2 that the metal catalyst particles prepared in Example 1 are uniform in size and uniform in distribution, and no agglomeration is found; the metal catalyst particles prepared in Comparative Example 1 are uneven in size and uneven in distribution, and obvious agglomeration occurs.

[0132] The metal catalysts prepared in Example 1, Example 4 and Comparative Example 1 were subjected to oxygen reduction linear scan test and cyclic voltammetry test. The test was carried out on a rotating disc electrode with a diameter of 5 mm, and the electrolyte was 0.1 M HCIO4 solution saturated with oxygen. The oxygen reduction scan rate was 5 mV / s, the electrode rotation speed was 1600 rpm, the cyclic voltammetry test potential scan speed was 50 mV / s, the test temperature was room temperature, and the test results are shown in Figures 3 to 6 .

[0133] Figure 3 and Figure 4The half-wave potential comparison chart and the cyclic voltammetry curve comparison chart of the oxygen reduction linear scan curves of the metal catalysts of Example 1 and Comparative Example 1, respectively, from which it can be seen that the half-wave potential of the oxygen reduction linear scan curve of the metal catalyst of Example 1 is about 17 mV higher than that of the catalyst of Comparative Example 1 with the same loading, and the electrochemical active area obtained by the cyclic voltammetry test is also larger. This shows that the metal catalyst prepared by the preparation method of the application has better performance, and the main reason is that the preparation method of the application can improve the uniformity of platinum particles loaded on the carbon carrier, and smaller and more uniformly distributed platinum particles are obtained, thereby improving the performance of the metal catalyst.

[0134] Figure 5 and Figure 6 The half-wave potential comparison chart and the cyclic voltammetry curve comparison chart of the oxygen reduction linear scan curves of the metal catalysts of Example 1 and Example 4, respectively, from which it can be seen that the half-wave potential of the oxygen reduction linear scan curve of the metal catalyst of Example 4 is about 40 mV higher than that of the catalyst of Example 1 with the same loading; and the electrochemical active area of Example 4 obtained by the cyclic voltammetry test is not much smaller than that of Example 1 after high-temperature treatment. This shows that the platinum-copper alloy fuel cell catalyst prepared by the application can effectively avoid particle agglomeration at high temperature, and an excellent fuel cell alloy catalyst is obtained.

[0135] The above only describes the preferred embodiments of the application and is not intended to limit the application. Any modifications, equivalent replacements and improvements made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method of preparing a metal catalyst, characterized by: The method comprises the following steps: dispersing and immersing carrier particles in a metal precursor solution to obtain a solid-liquid mixed system A; wherein the carrier particles comprise at least one of pure carbon carrier, metal-doped carbon carrier and non-metal atom-doped carbon carrier; the metal elements in the metal precursor solution comprise at least one of platinum, palladium, iridium, gold, iron, cobalt, nickel, copper and manganese; shearing and dispersing the solid-liquid mixed system A by using a shearing disperser with a corrosion-resistant cutter head to obtain a viscous slurry B; drying the viscous slurry B to obtain carrier particles C loaded with metal precursors; subjecting the carrier particles C loaded with metal precursors to reduction treatment in a reducing atmosphere and / or heat treatment in an inert atmosphere to obtain a metal catalyst; wherein the solid-liquid mixed system A is subjected to ultrasonic treatment before the shearing and dispersing treatment, and the shearing and dispersing treatment is carried out under heating; the ultrasonic treatment and the shearing and dispersing treatment are repeatedly operated alternately for multiple times until the viscous slurry B without visible water is obtained; the water in the viscous slurry B is not visible water, and the viscous slurry B comprises the following components by mass percentage: water 70%-85%, metal precursors 13%-15% and carrier particles 6%-8%.

2. The method of preparing a metal catalyst according to claim 1, characterized by: The metal precursor solution is a water-soluble metal salt solution or a water-soluble complex solution or a water-soluble alloy salt solution comprising at least one of platinum, palladium, iridium, gold, iron, cobalt, nickel, copper and manganese.

3. The method of preparing a metal catalyst according to claim 1, wherein: The concentration of the metal precursor solution is 0.05-0.32 mol / L, and the volume of the metal precursor solution is 1.5-10 times the tap density volume of the carrier particles; and / or, The metal loading of the metal catalyst is 40-80 wt%.

4. The method of preparing a metal catalyst according to claim 1, wherein: The carrier particles comprise at least one of acetylene black, activated carbon, carbon nanotube and graphene.

5. The method of preparing a metal catalyst according to claim 1, wherein: The shearing and dispersing treatment is carried out at a shearing and dispersing rotation speed of 1200-15000 rpm and a heating temperature of 50-90℃.

6. The method of preparing a metal catalyst according to claim 1, wherein: The gas of the reducing atmosphere comprises at least one of hydrogen, carbon monoxide and ammonia; and / or, The temperature of the reduction treatment is 60-800℃.

7. The method of preparing a metal catalyst according to claim 1, wherein: The gas of the inert atmosphere comprises argon or nitrogen; and / or, The temperature of the heat treatment is 60-800℃.

8. A metal catalyst characterized by: The metal catalyst is prepared by using the preparation method of any one of claims 1-7.

9. A fuel cell characterized by: The metal catalyst of claim 8 is used.

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