Preparation methods of carbon-supported metal catalysts and their application in fuel cells

Abstract

This application provides a method for preparing a carbon-supported metal catalyst and a carbon-supported metal catalyst in a fuel cell. The preparation method includes: mixing a metal precursor solution with a polymer compound to form filaments, resulting in a mixed system A; mixing mixed system A with a carbon support, at least partially entangling the polymer compound on the surface of the carbon support, resulting in a solid-liquid mixed system B; subjecting the solid-liquid mixed system B to vacuum evaporation to obtain a viscous slurry C; drying the viscous slurry C to obtain a carbon support D loaded with the metal precursor; and subjecting the carbon support D to reduction treatment in a reducing atmosphere and / or heat treatment in an inert atmosphere to obtain the carbon-supported metal catalyst. The use of a polymer compound to entangle the surface of the carbon support improves the wettability of the carbon support, allowing for uniform adsorption and precipitation of the metal precursor salt on the surface of the carbon support, increasing the metal loading, and improving the stability of the metal in the carbon support.

Description

Technical Field

[0001] This application belongs to the field of battery materials technology, and more specifically, relates to the preparation method of carbon-supported metal catalysts and carbon-supported metal catalysts in fuel cells. Background Technology

[0002] Fuel cells are clean and efficient energy conversion devices. Compared to traditional primary or secondary batteries, fuel cells have higher energy density and faster charging speeds. Compared to traditional heat engines, fuel cells have a much higher energy conversion rate. Moreover, in fuel cells, fuel is directly converted into "clean" combustion products such as water and carbon dioxide, with almost no emissions of sulfides and nitrogen oxides, making it a clean energy source.

[0003] Catalyst materials are crucial for fuel cells. Among them, platinum-based catalysts are widely considered the most important anode catalysts in direct fuel cells due to their excellent electronic properties. While platinum-based catalysts exhibit excellent catalytic performance, they also suffer from poor electrocatalytic stability and high cost. Improving platinum utilization, enhancing catalyst stability and resistance to poisoning are fundamental ways to reduce fuel cell costs.

[0004] To improve Pt utilization, Pt is typically loaded onto carbon support materials to enhance its dispersion. Simultaneously, the porous structure of the carbon support and carbon aggregates effectively improves mass transfer between reactants and products in the fuel cell catalyst layer, thereby enhancing fuel cell performance. To reduce catalyst layer thickness and decrease mass transfer resistance, fuel cells generally employ carbon-supported catalysts with high metal loadings (above 40 wt%).

[0005] Currently, the most commonly used method for preparing carbon-supported metal catalysts is the impregnation method. The basic principle of the traditional impregnation method is to utilize the adsorption effect of the support to adsorb the metal precursor onto the support. Specifically, the support is dispersed in a liquid or gas containing the metal precursor. The support is fully adsorbed (or not fully adsorbed) to reach impregnation equilibrium. Then, the liquid or gas is removed, followed by drying, calcination, activation, etc.

[0006] Traditional impregnation methods have been successfully applied in the preparation of three-way catalytic converters for automotive exhaust or liquefied petroleum gas conversion catalysts. This method is primarily suitable for preparing catalysts with low loading (<5%). However, when using traditional impregnation methods to prepare high-loading (40%-80%) fuel cell catalysts, two problems arise:

[0007] 1. Due to the low loading of metal catalysts, the carbon support surface cannot support a sufficient amount of metal precursors through equilibrium adsorption.

[0008] Second, because fuel cell supports generally have a high degree of graphitization and a hydrophobic surface, their wettability with the metal precursor solution is poor, which hinders the metal precursor solution from entering the pore structure of the carbon support and carbon aggregates during the impregnation process. This results in the metal precursor salt not being uniformly adsorbed and precipitated on the surface of the carbon support.

[0009] These problems result in low catalytic performance and stability of carbon-supported metal catalysts prepared by the traditional impregnation method with high catalyst loading. Summary of the Invention

[0010] Based on this, one objective of this application is to provide a method for preparing a carbon-supported metal catalyst, in order to solve the technical problems in the prior art where 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 support, resulting in low catalytic performance and stability of the carbon-supported metal catalyst.

[0011] Another objective of this application is to provide a carbon-supported metal catalyst.

[0012] Another object of this application is to provide a fuel cell.

[0013] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0014] A method for preparing a carbon-supported metal catalyst includes the following steps:

[0015] The metal precursor solution is mixed with a polymer compound, and the polymer compound forms filaments to obtain mixed system A.

[0016] Mixing system A with a carbon support, at least partially coating the surface of the carbon support with the polymer compound, yields solid-liquid mixture system B.

[0017] The solid-liquid mixture B was subjected to vacuum evaporation to obtain a viscous slurry C;

[0018] The viscous slurry C was dried to obtain a carbon support D loaded with a metal precursor.

[0019] The carbon support D is subjected to reduction treatment in a reducing atmosphere and / or heat treatment in an inert atmosphere to obtain a carbon-supported metal catalyst.

[0020] Optionally, the polymeric compound includes at least one of methylcellulose, polyvinyl alcohol, and polyvinylpyrrolidone; and / or,

[0021] The polymer is methylcellulose, and an aqueous solution of 2 wt% methylcellulose has a viscosity of 1-5000 mPa at 20°C.

[0022] Optionally, the amount of polymer compound added is 0.1%-100% of the mass of the carbon support.

[0023] Optionally, the metal element in the metal precursor solution includes at least one selected from platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese; and / or,

[0024] The metal precursor solution is a water-soluble metal salt solution, a water-soluble complex solution, or a water-soluble alloy salt solution containing at least one metal element selected from platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese.

[0025] Optionally, the carbon support includes at least one of acetylene black, activated carbon, carbon nanotubes, and graphene; and / or,

[0026] The concentration of the metal precursor solution is 0.06 mol / L-0.35 mol / L, and the volume of the metal precursor solution is 1.5-100 times the tap volume of the carbon support.

[0027] Optionally, the vacuum degree of the reduced pressure evaporation is less than 90 kPa; and / or,

[0028] Before vacuum evaporation, the solid-liquid mixture B is subjected to ultrasonic treatment; ultrasonic treatment and vacuum evaporation are repeated at least once alternately until a viscous slurry C without visible water is obtained.

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

[0030] Inert atmosphere gases include argon and / or nitrogen.

[0031] Optionally, the reduction treatment temperature is 60℃-800℃; and / or,

[0032] The heat treatment temperature is 60℃-800℃.

[0033] And a carbon-supported metal catalyst, prepared using any of the above-described methods for preparing carbon-supported metal catalysts.

[0034] And a fuel cell comprising the aforementioned carbon-supported metal catalyst.

[0035] 1. The method for preparing carbon-supported metal catalysts provided in this application involves mixing a polymer compound with a metal precursor solution to form filaments, which are then mixed with a carbon support. The polymer compound wraps around the surface of the carbon support, utilizing its water-retention capacity to improve the wettability of the carbon support, allowing the carbon metal precursor to penetrate into the pores of the carbon support and be uniformly loaded onto the surface of the carbon support. Then, the mixture is evaporated under reduced pressure to remove some water; drying is performed to remove all water, and the metal precursor precipitates and adheres to the surface of the carbon support; reduction and / or heat treatment are performed to reduce the metal cations, resulting in the carbon-supported metal catalyst. Compared with the prior art, the method for preparing carbon-supported metal catalysts in this application uses a water-soluble, filamentous polymer compound to wrap around the surface of the carbon support, improving the wettability of the carbon support, allowing the metal precursor salt to be uniformly adsorbed and precipitated on the surface of the carbon support, and increasing the metal loading in the carbon-supported metal catalyst, thereby improving the stability of the metal in the carbon support, i.e., improving the catalytic performance and stability of the carbon-supported metal catalyst.

[0036] 2. The carbon-supported metal catalyst provided in this application has a high metal loading and the metal is uniformly loaded on the surface of the carbon support, which improves the catalytic performance and stability of the carbon-supported metal catalyst.

[0037] 3. The fuel cell provided in this application uses the above-mentioned carbon-supported metal catalyst. The carbon-supported metal catalyst has high stability, which improves the utilization rate of the metal catalyst, thereby improving the catalytic performance and stability of the fuel cell and reducing material costs. Attached Figure Description

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0039] Figure 1 This is a transmission electron microscope (TEM) image of the metal catalyst of Example 1 of this application;

[0040] Figure 2 This is a transmission electron microscope (TEM) image of the metal catalyst of Comparative Example 1 of this application.

[0041] Figure 3 This is a comparison of the half-wave potential of the linear scan curves of oxygen reduction for the metal catalysts of Example 1 and Comparative Example 1 of this application.

[0042] Figure 4 This is a comparison of the cyclic voltammetry curves of the metal catalysts in Example 1 and Comparative Example 1 of this application;

[0043] Figure 5 This is a comparison of the half-wave potential of the linear scan curves of oxygen reduction for the metal catalysts of Example 4 and Comparative Example 2 of this application.

[0044] Figure 6This is a comparison of the cyclic voltammetry curves of the metal catalysts in Example 4 and Comparative Example 2 of this application. Detailed Implementation

[0045] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0046] This application provides a method for preparing a carbon-supported metal catalyst, comprising the following steps:

[0047] S10: The metal precursor solution is mixed with a polymer compound, and the polymer compound forms filaments to obtain a mixed system A.

[0048] After the polymer compound is mixed with the metal precursor solution, the polymer compound dissolves in the metal precursor solution and then forms a filamentous structure. The polymer compound is immersed in the metal precursor solution. The mixed system A includes the metal precursor and the filamentous polymer compound.

[0049] In some embodiments, the metal precursor solution and the polymer compound are mixed at room temperature with stirring. Stirring can accelerate the dissolution rate of the polymer compound and draw the polymer compound into filaments.

[0050] In some embodiments, the polymeric compound includes at least one of methylcellulose, polyvinyl alcohol, and polyvinylpyrrolidone, all of which are water-soluble, can form filaments in aqueous solutions, and have excellent water retention properties, which facilitate subsequent winding of the carbon support and increase the wettability of the carbon support by utilizing their excellent water retention properties.

[0051] In a preferred embodiment, the polymer compound is selected as methylcellulose, and an aqueous solution of 2 wt% methylcellulose has a viscosity of 1-5000 mPa at 20°C. This viscosity of methylcellulose allows it to wrap around the carbon support without causing agglomeration of the carbon support.

[0052] Optionally, the metal element in the metal precursor solution includes at least one selected from platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese, and 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 a suitable metal element can be selected as needed.

[0053] Optionally, the metal precursor solution is a water-soluble metal salt solution, a water-soluble complex solution, or a water-soluble alloy salt solution comprising at least one metal element selected from platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese. Understandably, the water-soluble metal salt is a salt of the corresponding metal element, the water-soluble complex is a complex of the corresponding metal element, and the water-soluble alloy salt is a salt of an alloy of at least two metal elements.

[0054] S20: Mix system A with a carbon support, such that at least a portion of the polymer compound is wrapped around the surface of the carbon support, to obtain a solid-liquid mixture B.

[0055] Mixed system A is mixed with carbon support. The polymer compound is partially wrapped around the surface of the carbon support. Its water retention capacity is used to improve the wettability of the carbon support, so that the metal precursor carbon can penetrate into the pores of the carbon support and be uniformly loaded on the surface of the carbon support.

[0056] In some embodiments, the mixture system A is mixed with the carbon support under ultrasonic and stirring conditions to improve the dispersibility of the system, and the polymer compound is wound onto the carbon support by the traction of stirring.

[0057] Optionally, the amount of polymer compound added is 0.1%-100% of the mass of the carbon support. This amount of polymer compound is sufficient to entangle the carbon support without wasting too much polymer compound.

[0058] Optionally, the carbon support includes at least one of acetylene black, activated carbon, carbon nanotubes, and graphene. Acetylene black, activated carbon, carbon nanotubes, and graphene have a three-dimensional interconnected ordered pore structure with a large specific surface area, which can provide a large adsorption space and is beneficial to improving the metal loading capacity.

[0059] In some embodiments, the concentration of the metal precursor solution is 0.06 mol / L-0.35 mol / L, and the volume of the metal precursor solution is 1.5-10 times the tapped volume of the carbon support. 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 carbon support is less than 1.5, the carbon support may not be completely immersed in the metal precursor solution, or the solid content of the solid-liquid mixture B may be high, making it difficult to disperse and prone to 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 carbon support is greater than 10, the solid content of the solid-liquid mixture B will be low, i.e., the concentration will be low. Although the dispersibility is good, it will increase the time of subsequent vacuum evaporation, reduce the processing efficiency, and is not economically efficient.

[0060] Therefore, during implementation, the volume of the metal precursor solution can be selected to be 1.5-10 times the volume of the carbon support. Within this volume ratio range, the carbon support can be completely immersed in the metal precursor solution. At the same time, the solid content of the solid-liquid mixture B is moderate, and the adsorption space of the carbon support matches the content of the metal precursor, thus avoiding the problem of material waste caused by excessive metal precursor.

[0061] S30: The solid-liquid mixture B is subjected to vacuum evaporation to obtain a viscous slurry C.

[0062] Vacuum evaporation can remove some moisture, mainly free water. The polymer compounds in this embodiment are water-soluble, and their solubility increases with temperature. Vacuum evaporation lowers the boiling point of the system, preventing the polymer compounds wrapped around the carbon support from dissolving due to increased temperature in the solid-liquid mixture B, thus ensuring the desired wrapping and wetting effect is achieved.

[0063] In this embodiment, "visible water" refers to water that is actually visible, meaning that there is no visible water in the viscous slurry C. The water in the viscous slurry C is internal and does not constitute visible water.

[0064] Optionally, the vacuum degree of reduced pressure evaporation is less than 90 kPa. Under this low pressure environment, the evaporation temperature of the system is greatly reduced, the solubility of the polymer compound does not increase or increases only slightly, and the polymer compound can maintain its entanglement and wetting of the carbon support.

[0065] Before vacuum evaporation, the solid-liquid mixture B is subjected to ultrasonic treatment; ultrasonic treatment and vacuum evaporation are repeated at least once alternately until a viscous slurry C without visible water is obtained.

[0066] The main components of the viscous slurry C are water, metal precursor, carbon support, and polymer compound. Understandably, the specific proportions of each component will vary depending on the feed ratio and specific operation. In some embodiments, the mass percentages of water, metal precursor, carbon support, and polymer compound in the viscous slurry C are 70%-85% water, 10%-18% metal precursor, 4.5%-10% carbon support, and 0.5%-2.5% polymer compound, respectively. The polymer compound is sufficient to coat the surface of the carbon support, and the water completely coats and fully wets the carbon support, allowing the metal precursor to be uniformly adsorbed onto the surface of the carbon support. Moreover, the ratio of metal precursor to carbon support is well-matched, providing a basis for increasing the metal loading.

[0067] S40: The viscous slurry C is dried to obtain a carbon support D loaded with a metal precursor.

[0068] The drying process removes all moisture, causing the metal precursor to precipitate and adhere to the surface of the carbon support. At this point, the metal salt, metal complex, or alloy salt adheres to the surface of the carbon support.

[0069] The drying process can be freeze-drying or heat-drying.

[0070] In some embodiments, the freeze-drying conditions are selected as follows: pressure below 10 Pa and temperature below -59°C. Under these conditions, the water will freeze rapidly and then sublimate, and the metal precursor will form a thin layer attached to the surface of the carbon support.

[0071] In some embodiments, the heating and drying temperature is 100°C-120°C, which causes the water to evaporate, the polymer compound to dissolve in the water and evaporate together with the water, and the metal precursor forms a thin layer attached to the surface of the carbon support.

[0072] S50: The carbon support D is placed in a reducing atmosphere for reduction treatment and / or heat-treated in an inert atmosphere to obtain a carbon-supported metal catalyst.

[0073] The anionic portion of the metal precursor is removed by reduction treatment and / or heat treatment, and the metal cations are reduced to obtain a carbon-supported metal catalyst.

[0074] In some embodiments, the anionic portion of the metal salt, metal complex, or alloy salt in the metal precursor is not easily decomposed by heat and needs to be reacted in a reducing atmosphere to reduce the metal ions to obtain the metal.

[0075] In some embodiments, the anionic portion of the metal salt, metal complex, or alloy salt in the metal precursor is easily decomposed by heat. In this case, the carbon support D can be heat-treated in an inert atmosphere to remove the anionic portion of the metal precursor, thereby reducing the metal ions to obtain the metal, without the need for further reduction treatment in a reducing atmosphere.

[0076] In some embodiments, the metal precursor requires a combination of heat treatment in an inert atmosphere and reduction treatment in a reducing atmosphere to completely reduce the metal ions to the target metal state. Therefore, at least one heat treatment is performed before or after the reduction treatment.

[0077] Therefore, reduction treatment in a reducing atmosphere and heat treatment in an inert atmosphere can be carried out together or separately, depending on the type of metal precursor.

[0078] Optionally, the reducing atmosphere includes at least one of hydrogen, carbon monoxide, and ammonia. These reducing gases have strong reducing properties and do not produce other side reactions that interfere with the loading of the target metal.

[0079] Optionally, the inert atmosphere includes argon and / or nitrogen, which do not react with the metal, protecting the metal from oxidation by air after reduction and allowing the target metal to be reduced smoothly.

[0080] Optionally, the reduction treatment temperature is 60℃-800℃ to provide sufficient energy to promote the reduction reaction to proceed in the forward direction.

[0081] In some embodiments, the heat treatment temperature can be selected according to the decomposition of anions, for example, the heat treatment temperature can be selected as 60℃-800℃.

[0082] Compared with the prior art, the preparation method of the carbon-supported metal catalyst in this application embodiment uses water-soluble, filamentous polymer compounds to wrap around the surface of the carbon support, thereby improving the wettability of the carbon support, enabling the metal precursor salt to be uniformly adsorbed and precipitated on the surface of the carbon support, and increasing the metal loading in the carbon-supported metal catalyst, thereby improving the stability of the metal in the carbon support, that is, improving the stability of the carbon-supported metal catalyst.

[0083] This application also provides a carbon-supported metal catalyst prepared by the above-described method. The carbon-supported metal catalyst has a high metal loading and the metal is uniformly loaded on the surface of the carbon support, which improves the stability of the carbon-supported metal catalyst.

[0084] The aforementioned carbon-supported metal catalysts can be applied to fuel cells. The high stability of carbon-supported metal catalysts improves the utilization rate of metal catalysts, thereby improving the stability of fuel cells and reducing material costs.

[0085] The following examples illustrate this point.

[0086] Example 1

[0087] The carbon-supported metal catalyst in this embodiment is a 40wt% platinum-carbon catalyst for fuel cells, with a total volume of 3g. Its preparation method includes the following steps:

[0088] S01: Add 50 ml of chloroplatinic acid solution (containing 6.15 mmol of chloroplatinic acid) to a container, add 450 mg of methylcellulose with a specification of 150 mPas, stir to dissolve, and the methylcellulose will be in the form of filaments to obtain mixed system A.

[0089] S02: Under stirring, add 1.8g of Ketjenblack EC-300J activated carbon to the container and mix it with the mixture system A, so that the activated carbon particles are completely immersed in the mixture system A. Sonicate for 30min, and the methylcellulose part is wrapped around the surface of the activated carbon particles to obtain the solid-liquid mixture system B.

[0090] S03: The solid-liquid mixture B is evaporated under reduced pressure while being stirred at 300 rpm to remove excess solvent until a viscous slurry C without visible water is obtained.

[0091] S04: After freezing the viscous slurry C in a refrigerator for 4 hours, freeze-dry it in a freeze dryer at a temperature below -59°C and a pressure below 10 Pa for 24 hours to obtain a carbon support D loaded with a metal precursor.

[0092] S05: The carbon support D was placed in a mixed atmosphere of 10% hydrogen and nitrogen and reduced at 120°C for 2 hours with a hydrogen flow rate of 10 ml / min. Then it was heat-treated at 300°C for 2 hours in a nitrogen atmosphere. After cooling, a platinum-carbon catalyst with a loading of 40 wt% for fuel cells was obtained.

[0093] Example 2

[0094] The carbon-supported metal catalyst in this embodiment is a 60wt% platinum-carbon catalyst for fuel cells, with a total weight of 100g. The preparation method includes the following steps:

[0095] S01: Add 1000ml of chloroplatinic acid solution (containing 307.7mmol of chloroplatinic acid) to a container, add 10g of methylcellulose with a specification of 150mPas, stir to dissolve, and the methylcellulose will be in the form of filaments to obtain mixed system A.

[0096] S02: Under stirring, add 40g of Ketjenblack EC-300J activated carbon to the container, so that the activated carbon particles are completely immersed in the precursor solution, mix with the mixture system A, so that the activated carbon particles are completely immersed in the mixture system A, and sonicate for 30min. The methylcellulose part is wrapped around the surface of the activated carbon particles to obtain the solid-liquid mixture system B.

[0097] S03: The solid-liquid mixture B is evaporated under reduced pressure while being stirred at 120 rpm until a viscous slurry C without visible water is obtained.

[0098] S04: After freezing the viscous slurry C in the cold trap of a freeze dryer for 8 hours, freeze-dry it in the freeze dryer at a temperature below -59°C and a pressure below 10 Pa for 24 hours to obtain a carbon support D loaded with a metal precursor.

[0099] S05: The carbon support D is placed in a mixed atmosphere of hydrogen and nitrogen and reduced at 120°C for 4 hours with a hydrogen flow rate of 200 ml / min. Then it is heat-treated at 300°C for 2 hours in a nitrogen atmosphere. After cooling, a platinum-carbon catalyst with a loading of 60 wt% for fuel cells is obtained.

[0100] Example 3

[0101] The carbon-supported metal catalyst in this embodiment is a 40wt% palladium-on-carbon catalyst for fuel cells, with a total content of 100mg. Its preparation method includes the following steps:

[0102] S01: Add 5 ml of palladium chloride solution to a container (containing 0.564 mmol of chloroplatinic acid), add 20 mg of methylcellulose with a specification of 150 mPas, stir to dissolve, and the methylcellulose will be in the form of filaments to obtain mixed system A.

[0103] S02: Under stirring, 90 mg of Ketjenblack EC-300J activated carbon is added to the container and mixed with the mixture system A, so that the activated carbon particles are completely immersed in the mixture system A. After ultrasonic dispersion for 30 min, the methylcellulose part is wrapped around the surface of the activated carbon, resulting in a solid-liquid mixture system B.

[0104] S03: The solid-liquid mixture B is evaporated under reduced pressure while being stirred at 1000 rpm until a viscous slurry C without visible water is obtained.

[0105] S04: After freezing the viscous slurry C in a refrigerator for 4 hours, freeze-dry it in a freeze dryer at a temperature below -59°C and a pressure below 10 Pa for 24 hours to obtain a carbon support D loaded with a metal precursor.

[0106] S05: The carbon support D is placed in a mixed atmosphere of 10% hydrogen and nitrogen and reduced at 80°C for 1 hour with a hydrogen flow rate of 10 ml / min. Then, it is heat-treated at 300°C for 1 hour in a nitrogen atmosphere. After cooling, a palladium-carbon catalyst with a loading of 40 wt% for fuel cells is obtained.

[0107] Example 4

[0108] The carbon-supported metal catalyst in this embodiment is a 40wt% platinum-cobalt carbon catalyst for fuel cells, with a total content of 100mg. Its preparation method includes the following steps:

[0109] S01: Add 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) to a container, add 30 mg of methylcellulose with a specification of 150 mPas, stir to dissolve, and the methylcellulose will be in the form of filaments to obtain mixed system A.

[0110] S02: Under stirring, 90 mg of Ketjenblack EC-300J activated carbon is added to the container and mixed with mixture A, so that the activated carbon particles are completely immersed in mixture A. After ultrasonic treatment for 30 min, the methylcellulose is partially wrapped around the surface of the activated carbon particles, resulting in solid-liquid mixture B.

[0111] S03: The solid-liquid mixture B is evaporated under reduced pressure while being stirred at 1000 rpm until a viscous slurry C without visible water is obtained.

[0112] S04: After freezing the viscous slurry C in a refrigerator for 4 hours, freeze-dry it in a freeze dryer at a temperature below -59°C and a pressure below 10 Pa for 24 hours to obtain a carbon support D loaded with a metal precursor.

[0113] S05: The carbon support D was placed in a mixed atmosphere of 10% hydrogen and nitrogen and reduced at 300°C for 2 hours with a hydrogen flow rate of 10 ml / min. Then, it was heat-treated at 600°C for 6 hours in a nitrogen atmosphere. After cooling, a platinum-copper-carbon catalyst with a loading of 40 wt% for fuel cells was obtained.

[0114] Comparative Example 1

[0115] The carbon-supported metal catalyst in this comparative example is a 40% platinum-carbon catalyst for fuel cells, with a total volume of 3g. Its preparation method includes the following steps:

[0116] S01: Add 50 ml of chloroplatinic acid solution (containing 6.15 mmol of chloroplatinic acid) to the container, and then add 1.8 g of Ketjenblack EC-300J activated carbon to the container, so that the activated carbon particles are completely immersed in the precursor solution, and mix system A.

[0117] S02: Sonicate the mixture A for 30 minutes to obtain the solid-liquid mixture B.

[0118] S03: While stirring the solid-liquid mixture B at 300 rpm, heat it to 80°C to evaporate excess solvent until a viscous slurry C without visible water is obtained.

[0119] S04: After freezing the viscous slurry C in a refrigerator for 4 hours, freeze-dry it in a freeze dryer at a temperature below -59°C and a pressure below 10 Pa for 24 hours to obtain a carbon support D loaded with a metal precursor.

[0120] S05: The carbon support D was placed in a 10% hydrogen atmosphere and reduced at 120°C for 2 hours with a hydrogen flow rate of 10 ml / min. Then, it was heat-treated at 300°C for 2 hours in a nitrogen atmosphere. After cooling, a platinum-carbon catalyst with a loading of 40 wt% for fuel cells was obtained.

[0121] Comparative Example 2

[0122] The preparation method of this comparative example is basically the same as that of Example 4, except that no methylcellulose is added to this comparative example.

[0123] Transmission electron microscopy (TEM) was performed on the carbon-supported metal catalysts prepared in Example 1 and Comparative Example 1, respectively. The results are as follows: Figure 1 and Figure 2 As shown. Based on Figure 1 and Figure 2 It can be seen that the carbon-supported metal catalyst particles prepared in Example 1 are uniform in size and distribution, and no agglomeration was found; while the carbon-supported metal catalyst particles prepared in Comparative Example 1 are uneven in size and distribution, and obvious agglomeration occurred.

[0124] The carbon-supported metal catalysts prepared in Examples 1 and 4, and Comparative Examples 1 and 2, were subjected to oxygen reduction linear scan and cyclic voltammetry tests. The tests were conducted on a rotating disk electrode with a diameter of 5 mm, using an oxygen-saturated 0.1 M HClO4 solution as the electrolyte. The oxygen reduction scan rate was 5 mV / s, and the electrode rotation speed was 1600 rpm. The cyclic voltammetry test potential scan rate was 50 mV / s, and the test temperature was room temperature. The test results are as follows: Figures 3 to 6 As shown.

[0125] Figure 3 and Figure 4 The figures show a comparison of the half-wave potential and cyclic voltammetry curves of the oxygen reduction linear scan curves for Example 1 and Comparative Example 1, respectively. As can be seen from the figures, the half-wave potential of the oxygen reduction linear scan curve of the carbon-supported metal catalyst in Example 1 is approximately 23 mV higher than that of the carbon-supported metal catalyst in Comparative Example 1 with the same loading. Simultaneously, the electrochemical active area obtained from the cyclic voltammetry test increases by 25%. This indicates that the carbon-supported metal catalyst prepared using the method of this application has a smaller particle size and more uniform distribution compared to the carbon-supported metal catalyst in Comparative Example 1, and exhibits better oxygen reduction catalytic activity.

[0126] Figure 5 and Figure 6 The figures show a comparison of the half-wave potential and cyclic voltammetry curves of the oxygen reduction linear scan curves for the carbon-supported metal catalysts of Example 4 and Comparative Example 2, respectively. As can be seen from the figures, the half-wave potential of the oxygen reduction linear scan curve of the carbon-supported metal catalyst of Example 4 is approximately 26 mV higher than that of the catalyst of Comparative Example 2 with the same loading. Simultaneously, the electrochemical active area obtained from the cyclic voltammetry test increases by 31%. This indicates that the carbon-supported metal catalyst prepared using the method of this application has a smaller particle size, a more uniform distribution, and better oxygen reduction catalytic activity.

[0127] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a carbon-supported metal catalyst, characterized in that: Includes the following steps: A metal precursor solution is mixed with a polymer compound, which forms filaments to obtain a mixed system A. The mixture system A is mixed with a carbon support, such that at least part of the polymer compound is wrapped around the surface of the carbon support, to obtain a solid-liquid mixture system B; The solid-liquid mixture B was subjected to vacuum evaporation to remove free water, resulting in a viscous slurry C. The viscous slurry C was freeze-dried to obtain a carbon support D loaded with a metal precursor. The carbon support D is subjected to reduction treatment in a reducing atmosphere and / or heat treatment in an inert atmosphere to obtain a carbon-supported metal catalyst.

2. The method for preparing the carbon-supported metal catalyst as described in claim 1, characterized in that: The polymeric compound includes at least one of methylcellulose, polyvinyl alcohol, and polyvinylpyrrolidone.

3. The method for preparing the carbon-supported metal catalyst as described in claim 2, characterized in that: The polymer compound is methylcellulose, and an aqueous solution of the methylcellulose at a concentration of 2wt% has a viscosity of 1-5000 mPa·s at 20°C.

4. The method for preparing the carbon-supported metal catalyst according to any one of claims 1-3, characterized in that: The amount of the polymer compound added is 0.1%-100% of the mass of the carbon carrier.

5. The method for preparing the carbon-supported metal catalyst as described in claim 1, characterized in that: The metal precursor solution contains at least one of the following metal elements: platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese; and / or, The metal precursor solution is a water-soluble metal salt solution, a water-soluble complex solution, or a water-soluble alloy salt solution containing at least one metal element selected from platinum, palladium, iridium, gold, iron, cobalt, nickel, copper, and manganese.

6. The method for preparing the carbon-supported metal catalyst as described in claim 1, characterized in that: The carbon support includes at least one of acetylene black, activated carbon, carbon nanotubes, and graphene; and / or, The concentration of the metal precursor solution is 0.06 mol / L to 0.35 mol / L, and the volume of the metal precursor solution is 1.5 to 100 times the tap volume of the carbon support.

7. The method for preparing the carbon-supported metal catalyst as described in claim 1, characterized in that: The vacuum degree of the reduced pressure evaporation is less than 90 kPa; and / or, Prior to the vacuum evaporation process, the solid-liquid mixture B is subjected to ultrasonic treatment; the ultrasonic treatment and the vacuum evaporation are repeated at least once in an alternating manner until a viscous slurry C without visible water is obtained.

8. The method for preparing the carbon-supported metal catalyst as described in claim 1, characterized in that: The reducing atmosphere includes at least one of hydrogen, carbon monoxide, and ammonia; and / or, The inert atmosphere includes argon and / or nitrogen.

9. The method for preparing the carbon-supported metal catalyst as described in claim 1, characterized in that: The reduction treatment is performed at a temperature of 60℃-800℃; and / or, The heat treatment temperature is 60℃-800℃.

10. A carbon-supported metal catalyst, characterized in that: It is prepared using the method for preparing carbon-supported metal catalysts as described in any one of claims 1 to 9.

11. A fuel cell, characterized in that: Including the carbon-supported metal catalyst of claim 10.

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