Platinum alloy catalyst, preparation method thereof and fuel cell

Abstract

The invention relates to a platinum alloy catalyst, a preparation method thereof and a fuel cell, the platinum alloy catalyst comprises a nitrogen-modified carbon carrier and an active component loaded on the nitrogen-modified carbon carrier, the platinum alloy comprises a platinum-nickel alloy and / or a platinum-cobalt alloy; the surface of the nitrogen-modified carbon carrier contains pyridine nitrogen and / or pyrrole nitrogen. According to the platinum alloy catalyst provided by the invention, the carbon carrier is modified by nitrogen, so that the platinum alloy and carbon nitrogen on the carrier form a coordinate bond, so that the platinum alloy is firmly anchored on the carbon carrier, and the bottlenecks that the binding force of a commercial catalyst platinum reduction attached carbon carrier is relatively weak and the durability of the catalyst is poor due to the increase of the particle size of Oswald cured platinum are broken through; the weak interaction mode that a traditional catalyst only depends on physical adsorption is changed essentially, the strong chemical bonding effect effectively inhibits platinum atom migration and particle coarsening phenomena caused by the curing effect in the electrochemical cycle process, and the electrochemical activity and durability of the catalyst are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a platinum alloy catalyst, a preparation method thereof, and a fuel cell. Background Art

[0002] Addressing global energy consumption and environmental pollution caused by fossil fuel use has spurred the growth of renewable and environmentally friendly energy solutions worldwide. The renewable energy-based hydrogen economy—including hydrogen production, storage, and conversion into electricity—is widely considered a promising solution for future energy. Within this hydrogen economy, fuel cells are crucial for providing low-carbon transportation.

[0003] Fuel cells are considered to be an important development direction in the future energy field due to their high efficiency, cleanliness and renewability. Generally speaking, platinum-carbon catalysts are the most widely used fuel cell catalysts in scientific research and commercial cases, mainly due to their high catalytic activity and better stability in strong acidic electrolytes. However, the commercial application of platinum-carbon catalysts is still seriously hindered by several problems, especially platinum is a relatively expensive metal that easily dissolves and aggregates under poor operating conditions, resulting in poor electrocatalytic activity and stability of the catalyst. In addition, the carbon support corrodes due to surface electrochemical oxidation, which may lead to the dissolution and aggregation of platinum nanoparticles. Therefore, efficient and stable catalysts are needed to promote the oxygen reduction reaction (ORR), which is the key to cathode reduction in fuel cells.

[0004] CN110021759A discloses a method for preparing a platinum-nickel alloy catalyst, comprising: preparing a mixed raw material of graphene and nickel nitrate in proportion; performing ultrasonic mixing, transferring the raw material into a microwave oven for microwave reduction reaction after the ultrasonic mixing is completed, air-cooling the raw material to room temperature after the reduction reaction is completed, and sealing the raw material with plastic wrap; placing a magnetron in a container, stirring the raw material on a magnetic stirrer for more than 12 hours, adding deionized water, and then filtering the raw material, placing the filter cake in a crucible, and transferring the filter cake to a vacuum drying oven for drying, grinding the dried filter cake to obtain a PtNi / GN catalyst; analyzing the effects of the catalyst on its electrocatalytic ability through X-ray diffractometry and electrochemical testing, and selecting a PtNi / GN catalyst based on the analysis results.

[0005] CN1162072A discloses a nitrogen-doped carbon-coated platinum-nickel alloy nanomaterial, its preparation method and application. The nanomaterial has a core-shell structure with a core of platinum-nickel alloy nanoparticles and a shell of nitrogen-doped carbon cages. The platinum-nickel alloy nanoparticles are solid and / or porous structures. The carbon-coated platinum-nickel alloy nanomaterial has good electrocatalytic properties.

[0006] However, the platinum alloy catalysts provided in the above solutions and the prior art all have the problem of poor durability. Therefore, how to develop a highly active and durable platinum alloy catalyst and a preparation method thereof has become an urgent problem to be solved. Summary of the Invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide a platinum alloy catalyst, a preparation method thereof, and a fuel cell. The platinum alloy catalyst of the present invention modifies a carbon support by nitrogen, thereby improving the electronic structure and chemical properties of the carbon support. By alloying platinum with low-cost metals, not only the catalyst cost is reduced, but also the catalytic activity and durability are improved by nitrogen-modifying the platinum alloy particles loaded on the carbon support.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a platinum alloy catalyst, which includes a nitrogen-modified carbon support and an active component loaded on the nitrogen-modified carbon support, wherein the active component includes a platinum alloy; the platinum alloy includes a platinum-nickel alloy and / or a platinum-cobalt alloy; and the surface of the nitrogen-modified carbon support contains pyridinic nitrogen and / or pyrrolic nitrogen.

[0010] The platinum alloy catalyst provided by the present invention has excellent electrochemical activity and excellent durability. The nitrogen-modified carbon support forms a coordination bond between the platinum alloy and the carbon and nitrogen on the support, thereby firmly anchoring the platinum alloy on the carbon support. This breaks through the bottleneck of weak bonding of commercial catalysts to the carbon support due to platinum reduction and increased platinum particle size during Oswald ripening, resulting in poor catalyst durability. It essentially changes the weak interaction mode of traditional catalysts that only relies on physical adsorption. This strong chemical bonding effectively suppresses the migration of platinum atoms and particle coarsening caused by the ripening effect during the electrochemical cycle, thereby improving the electrochemical activity and durability of the catalyst.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, the platinum loading of the platinum alloy catalyst is 20wt%-50wt%, for example, it can be 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, 32wt%, 35wt%, 38wt%, 40wt%, 42wt%, 45wt%, 48wt% or 50wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] Preferably, the nitrogen-modified carbon support is prepared by the following method:

[0014] The carbon support is mixed with mixed acid for pre-oxidation to obtain a pre-oxidized carbon support; and the pre-oxidized carbon support is heat-treated in an atmosphere of ammonia and argon to obtain a nitrogen-modified carbon support.

[0015] The method of nitrogen-modified carbon carrier is simple and efficient. The nitrogen element is introduced on the surface of the carbon carrier by heat treatment in an ammonia and argon atmosphere. The oxygen-containing functional groups can react chemically with the nitrogen-containing precursor, so that the nitrogen atoms can be more stably bound to the carbon carrier. Oxidation pretreatment will affect the pore structure of the carbon carrier. On the one hand, the oxidation process may etch the carbon surface, increase the number and size of pores, and thus increase the specific surface area of ​​the carbon carrier. A larger specific surface area means that there is more surface available for nitrogen doping, which increases the contact opportunities between nitrogen atoms and the carbon surface.

[0016] On the other hand, a suitable pore structure also facilitates the diffusion of reactants and products, improving the efficiency of the catalytic reaction. As the nitrogen doping level increases, excessive nitrogen doping can damage the carbon structure, leading to reduced performance of the carbon support. Therefore, dual oxidation pretreatment helps to control the amount and distribution of nitrogen doping to a certain extent, avoiding damage to the carbon structure caused by excessive doping and achieving optimal performance of the nitrogen-doped carbon support.

[0017] The present invention directly fixes the pyrrole ring through chemical oxidative polymerization, avoiding the uncertainty of high-temperature pyrolysis and achieving a pyrrole nitrogen content greater than 90%. The defect sites formed by the acid oxidation pretreatment of the present invention induce the dehydrogenation rearrangement of the pyrrole ring to pyridinic nitrogen during subsequent heat treatment, achieving the precise construction of dual active sites. When regulating the nitrogen-doped carbon support, the agglomeration of metal atoms in processes such as high temperatures can be effectively avoided, ensuring high dispersion of metal atoms on the support. The nitrogen-doped carbon support regulated by the dual oxidation pretreatment enhances its catalytic activity by improving the interaction between metal atoms, coordinating atoms, and the support.

[0018] Preferably, the amount of the mixed acid added is excessive so that the carbon support is immersed in the mixed acid. For example, the volume ratio of the carbon support to the mixed acid is 1:(5-50), for example, 1:5, 1:10, 1:15, 1:20, 1:30, 1:40, 1:45 or 1:50, but is not limited to the listed values. Other values ​​within the numerical range not listed are also applicable.

[0019] Preferably, the carbon support comprises any one or a combination of at least two of ketjen EC300J, ketjen EC600J or carbon nanotubes. Typical but non-limiting combinations include a combination of ketjen EC300J and ketjen EC600J, a combination of ketjen EC600J and carbon nanotubes, a combination of ketjen EC300J and carbon nanotubes, and a combination of ketjen EC300J, ketjen EC600J and carbon nanotubes.

[0020] Preferably, the mixed acid comprises sulfuric acid and nitric acid.

[0021] Preferably, the volume ratio of sulfuric acid to nitric acid is (2-4):1, for example, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the pre-oxidation temperature is 70°C-90°C, for example, it can be 70°C, 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, 88°C or 90°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the pre-oxidation time is 3 h-6 h, for example, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the volume ratio of ammonia to argon is (90-95):(5-10), for example, it can be 90:10, 91:9, 92:8, 93:7, 94:6 or 95:5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the heat treatment includes a first heat treatment and a second heat treatment.

[0026] Preferably, the temperature of the first step heat treatment is 300°C-500°C, for example, it can be 300°C, 320°C, 350°C, 380°C, 400°C, 420°C, 450°C, 480°C or 500°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the first heat treatment time is 1 h-3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the temperature of the second step heat treatment is 700℃-900℃, for example, it can be 700℃, 720℃, 750℃, 780℃, 800℃, 820℃, 850℃, 880℃ or 900℃, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] The present invention further preferably adopts a two-step heat treatment method to introduce nitrogen elements on the surface of the carbon support, and the first step of heat treatment is used for pre-stabilization of the precursor. A large amount of volatile small molecules, such as H2O, CO2, NH3, HCN, etc., are released at low temperatures. These components can be gently driven out to avoid the collapse of the material structure, splashing or the formation of other by-products due to violent decomposition during subsequent high-temperature treatment. The nitrogen atoms can be more orderly and effectively incorporated into the gradually formed carbon structure, thereby increasing the nitrogen doping amount and the nitrogen retention rate. An intermediate stable structure is formed, which promotes the precursor to undergo preliminary cross-linking, cyclization or carbonization reactions, forming a relatively stable intermediate carbon skeleton. This skeleton provides the structural basis for the second step of high-temperature treatment.

[0030] The second heat treatment step is for efficient nitrogen doping and bonding. At high temperatures, the activity of NH3 is enhanced, which can more effectively insert or replace nitrogen atoms into the carbon skeleton, forming stable C-N bonds.

[0031] Controlling nitrogen morphology (pyrrolic / pyridinic nitrogen). High temperatures are key to regulating nitrogen species morphology. Pyridinic nitrogen typically requires higher temperatures for stable formation (especially at edge / defect sites). The formation of pyrrolic nitrogen is also related to cyclization reactions within a specific temperature window.

[0032] Graphitization degree control. High temperature helps to increase the graphitization degree of carbon materials and improve electrical conductivity.

[0033] Preferably, the time of the second heat treatment is 1 h-3 h, for example, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Preferably, after the heat treatment and before obtaining the nitrogen-modified carbon support, the process further includes acid washing, washing and drying.

[0035] Preferably, the acid used in the pickling process comprises dilute nitric acid.

[0036] In a second aspect, the present invention provides a method for preparing the platinum alloy catalyst as described in the first aspect, the preparation method comprising the following steps:

[0037] The carbon support is mixed with a mixed acid for pre-oxidation to obtain a pre-oxidized carbon support; the pre-oxidized carbon support is heat-treated in an atmosphere of ammonia and argon to obtain a nitrogen-modified carbon support;

[0038] A nitrogen-modified carbon support, a platinum source solution and a transition metal source solution are mixed, reacted and calcined to obtain a platinum alloy catalyst.

[0039] The present invention first pre-treats the carbon support with double oxidation to construct a surface functional group array containing carboxyl / epoxy groups, which is more conducive to the introduction of nitrogen-containing functional groups. The platinum source solution and the transition metal source solution can be mixed first, and after they are completely dispersed, the nitrogen-modified carbon support is added. After the reaction, the metal ions are thoroughly impregnated into the pores of the carbon support to achieve uniform dispersion of the active components.

[0040] Preferably, the platinum source includes any one of chloroplatinic acid, platinum nitrate, platinum sulfate, ammonium chloroplatinate or platinum dichloride, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of chloroplatinic acid and platinum nitrate, a combination of platinum sulfate and ammonium chloroplatinate, a combination of platinum nitrate and platinum sulfate, a combination of chloroplatinic acid and platinum sulfate, a combination of platinum sulfate, ammonium chloroplatinate and platinum dichloride, a combination of chloroplatinic acid, platinum nitrate, platinum sulfate and platinum dichloride, and a combination of chloroplatinic acid, platinum nitrate, platinum sulfate, ammonium chloroplatinate and platinum dichloride. Chloroplatinic acid is preferred.

[0041] Preferably, the transition metal source includes a nickel source and / or a cobalt source.

[0042] Preferably, the nickel source comprises any one or a combination of at least two of nickel chloride, nickel nitrate or nickel sulfate. Typical but non-limiting combinations include a combination of nickel chloride and nickel nitrate, a combination of nickel nitrate and nickel sulfate, a combination of nickel chloride and nickel sulfate, and a combination of nickel chloride, nickel nitrate and nickel sulfate, preferably nickel chloride.

[0043] Preferably, the cobalt source comprises any one or a combination of at least two of cobalt chloride, cobalt nitrate or cobalt sulfate. Typical but non-limiting combinations include a combination of cobalt chloride and cobalt nitrate, a combination of cobalt nitrate and cobalt sulfate, a combination of cobalt chloride and cobalt sulfate, a combination of cobalt chloride, cobalt nitrate and cobalt sulfate, preferably cobalt chloride.

[0044] Preferably, the molar ratio of platinum ions to transition metal ions in the platinum source solution and the transition metal source solution is 1:(0.3-1), for example, it can be 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8 or 1:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the reaction temperature is 70°C-80°C, for example, 70°C, 72°C, 74°C, 75°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, the reaction time is 10 h-20 h, for example, 10 h, 12 h, 14 h, 16 h, 18 h or 20 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, solid-liquid separation and drying treatment are further performed after the reaction and before calcination.

[0048] Preferably, the temperature of the drying treatment is 50°C-80°C, for example, it can be 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the drying time is 5 h-10 h, for example, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] Preferably, the calcination temperature is 600°C-900°C, for example, it can be 600°C, 620°C, 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C or 900°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] Preferably, the calcination atmosphere is an inert gas.

[0052] Preferably, the inert gas includes argon and hydrogen.

[0053] Preferably, the volume ratio of argon and hydrogen is (90-95):(5-10), for example, it can be 90:10, 91:9, 92:8, 93:7, 94:6 or 95:5, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] The present invention further controls the calcination temperature to be 600° C.-900° C. During this process, alloying of platinum and transition metal is achieved in an inert atmosphere. The calcination has the following effects:

[0055] (1) Removal of volatile components: The calcination process decomposes, oxidizes or volatilizes these organic substances at high temperatures, leaving behind pure inorganic catalyst materials. This is the key to obtaining highly active catalysts, as residual organic matter can block active sites.

[0056] (2) Promote crystallization and crystal phase formation: Catalyst precursors (before calcination, they are usually amorphous or in an intermediate state with low crystallinity and inaccurate stoichiometric ratio. High-temperature calcination provides energy to drive atomic rearrangement and diffusion, leading to the formation of a specific crystal structure with high catalytic activity;

[0057] (3) Stabilize catalyst particles and enhance interaction with the support: For supported catalysts, calcination helps to strengthen the binding force between active metal / metal oxide particles and the support. This can improve the mechanical and electrochemical stability of the catalyst and reduce the shedding, migration, and agglomeration of active components during fuel cell operation.

[0058] (4) Adjusting chemical composition and oxidation state: The calcination environment (atmosphere) can control the final oxidation state of the metal element. Calcination in an inert atmosphere (such as N2, Ar) or a reducing atmosphere (such as H2, H2 / N2 mixed gas) can reduce the metal oxide precursor to a metallic state (such as Pt 0 ); For alloy catalysts (such as PtCo, PtNi), calcination is the key step to form a uniform alloy phase;

[0059] (5) Increase specific surface area and porosity: Calcination under appropriate conditions, especially when a large amount of organic matter is removed, helps to form or retain a certain porous structure, increase the specific surface area of ​​the catalyst, and expose more active sites.

[0060] However, too high a temperature or too long a calcination time will cause small particles to fuse into large particles, which will in turn reduce the specific surface area and activity.

[0061] Preferably, the calcination time is 3 h-6 h, for example, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0062] As a preferred technical solution of the preparation method of the present invention, the preparation method comprises the following steps:

[0063] (1) mixing the carbon support with a mixed acid of sulfuric acid and nitric acid in a volume ratio of (2-4):1 at a carbon support to mixed acid volume ratio of 1:(5-50), and pre-oxidizing at 70°C-90°C for 3h-6h to obtain a pre-oxidized carbon support;

[0064] (2) heat treating the pre-oxidized carbon support in an atmosphere with a volume ratio of ammonia to argon of (90-95):(5-10), wherein the heat treatment steps are as follows: a first heat treatment at 300°C-500°C for 1h-3h, and then a second heat treatment at 700°C-900°C for 1h-3h, followed by washing with nitric acid and water until neutral, and then drying at 50°C-70°C for 5h-10h to obtain a nitrogen-modified carbon support;

[0065] (3) mixing a nitrogen-modified carbon support, chloroplatinic acid, and a transition metal source solution, stirring and reacting at 70°C-80°C for 10-20 hours, filtering, drying at 50°C-80°C for 5-10 hours, and calcining at 600°C-900°C for 3-6 hours in an atmosphere of argon and hydrogen at a volume ratio of (90-95):(5-10) to obtain a platinum alloy catalyst;

[0066] The molar ratio of platinum ions to transition metal ions in the platinum source solution and the transition metal source solution is 1:(0.3-1).

[0067] In a third aspect, the present invention provides a fuel cell comprising the platinum alloy catalyst described in the first aspect.

[0068] The fuel cell provided by the present invention has better durability. The alloy forms coordination bonds with the carbon and nitrogen on the carrier, thereby firmly anchoring the platinum alloy on the carbon carrier. This breaks through the bottleneck of weak bonding between commercial platinum reduction and carbon carrier and increased Oswald ripening platinum particle size leading to poor catalyst durability. It fundamentally changes the weak interaction mode of traditional catalysts that only rely on physical adsorption. This strong chemical bonding effectively suppresses the migration of platinum atoms and particle coarsening caused by the ripening effect during the electrochemical cycle, thereby improving the catalyst and durability.

[0069] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0070] Compared with the prior art, the present invention has at least the following beneficial effects:

[0071] The platinum alloy catalyst provided by the present invention has excellent electrochemical activity and excellent durability. The nitrogen-modified carbon support forms a coordination bond between the platinum alloy and the carbon and nitrogen on the support, thereby firmly anchoring the platinum alloy on the carbon support. This breaks through the bottleneck of weak bonding of commercial catalysts to the carbon support due to platinum reduction and increased platinum particle size during Oswald ripening, resulting in poor catalyst durability. It essentially changes the weak interaction mode of traditional catalysts that only relies on physical adsorption. This strong chemical bonding effectively suppresses the migration of platinum atoms and particle coarsening caused by the ripening effect during the electrochemical cycle, thereby improving the electrochemical activity and durability of the catalyst. DETAILED DESCRIPTION

[0072] The technical solution of the present invention will be further described below by way of specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention, which shall be subject to the claims.

[0073] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0074] Example 1

[0075] This embodiment provides a platinum alloy catalyst, which includes a nitrogen-modified carbon support and a platinum-nickel alloy supported on the nitrogen-modified carbon support with a platinum loading of 20 wt%;

[0076] The preparation method of the platinum alloy catalyst provided in this embodiment comprises the following steps:

[0077] (1) mixing Ketjen EC300J with a mixed acid of sulfuric acid and nitric acid in a volume ratio of 2:1, and pre-oxidizing at 70°C for 4 hours to obtain a pre-oxidized carbon support;

[0078] (2) The pre-oxidized ketjen EC300J was heat treated in an atmosphere with a volume ratio of NH3 / Ar of 95:5. The heat treatment steps were as follows: a first heat treatment at 300°C for 3 h, a second heat treatment at 900°C for 1 h, a nitric acid acid wash, a water wash to neutrality, and then a drying at 50°C for 6 h to obtain a nitrogen-modified carbon support;

[0079] (3) mixing a nitrogen-modified carbon support, a chloroplatinic acid solution, and a nickel chloride hexahydrate solution, stirring and reacting at 70°C for 12 hours, filtering, drying at 50°C for 6 hours, and calcining at 700°C for 4 hours in an atmosphere of argon and hydrogen with a volume ratio of 95:5. The calcined powder was acid-washed with dilute nitric acid at 60°C for 4.5 hours, washed with deionized water until neutral, and finally dried in a vacuum drying oven to obtain a platinum alloy catalyst;

[0080] The molar ratio of platinum ions to nickel ions in the chloroplatinic acid solution and the nickel chloride hexahydrate solution is 1:0.3.

[0081] Example 2

[0082] This embodiment provides a platinum alloy catalyst, which includes a nitrogen-modified carbon support and a platinum-nickel alloy supported on the nitrogen-modified carbon support with a platinum loading of 40 wt%;

[0083] The preparation method of the platinum alloy catalyst provided in this embodiment comprises the following steps:

[0084] (1) mixing Ketjen EC600J with a mixed acid of sulfuric acid and nitric acid in a volume ratio of 3:1, and pre-oxidizing at 80°C for 3 h to obtain a pre-oxidized carbon support;

[0085] (2) The pre-oxidized ketjen EC600J was heat treated in an atmosphere with a volume ratio of NH3 / Ar of 95:5. The heat treatment steps were as follows: a first heat treatment at 400°C for 2.5 hours, and then a second heat treatment at 800°C for 2 hours. After washing with nitric acid and water until neutral, the carbon support was dried at 50°C for 6 hours to obtain a nitrogen-modified carbon support.

[0086] (3) mixing a nitrogen-modified carbon support, a platinum nitrate solution, and a nickel nitrate solution, stirring and reacting at 70°C for 12 hours, filtering, drying at 50°C for 6 hours, and calcining at 800°C for 2 hours in an atmosphere of argon and hydrogen with a volume ratio of 95:5. The calcined powder was acid-washed with dilute nitric acid at 60°C for 5 hours, washed with deionized water until neutral, and finally dried in a vacuum drying oven to obtain a platinum alloy catalyst;

[0087] The molar ratio of platinum ions to nickel ions in the platinum nitrate solution and the nickel nitrate solution is 1:0.5.

[0088] Example 3

[0089] This embodiment provides a platinum alloy catalyst, the platinum alloy catalyst comprising a nitrogen-modified carbon support and a platinum-cobalt alloy supported on the nitrogen-modified carbon support with a platinum loading of 50 wt%;

[0090] The preparation method of the platinum alloy catalyst provided in this embodiment comprises the following steps:

[0091] (1) mixing carbon nanotubes with a mixed acid of sulfuric acid and nitric acid in a volume ratio of 2:1, and pre-oxidizing at 80°C for 3 h to obtain a pre-oxidized carbon support;

[0092] (2) The pre-oxidized carbon nanotubes were heat treated in an atmosphere with a volume ratio of NH3 / Ar of 95:5. The heat treatment steps were as follows: a first heat treatment at 300°C for 3 h, and then a second heat treatment at 700°C for 3.5 h. After washing with nitric acid and water until neutral, the carbon nanotubes were dried at 50°C for 6 h to obtain nitrogen-modified carbon supports.

[0093] (3) mixing a nitrogen-modified carbon support, a platinum sulfate solution, and a cobalt sulfate solution, stirring and reacting at 70°C for 12 hours, filtering, drying at 50°C for 6 hours, and calcining at 900°C for 1 hour in an atmosphere of argon and hydrogen with a volume ratio of 95:5. The calcined powder was acid-washed with dilute nitric acid at 80°C for 4 hours, washed with deionized water until neutral, and finally dried in a vacuum drying oven to obtain a platinum alloy catalyst;

[0094] The molar ratio of platinum ions to cobalt ions in the platinum sulfate solution and the cobalt sulfate solution is 1:0.5.

[0095] Example 4

[0096] This embodiment provides a platinum alloy catalyst, which differs from Example 1 only in that, when preparing the platinum alloy catalyst, the heat treatment step (2) is as follows: heat treatment is performed at 300°C for 4 hours, and heat treatment at 900°C is not performed, and the other steps remain unchanged.

[0097] Example 5

[0098] This embodiment provides a platinum alloy catalyst, which differs from Example 1 only in that, when preparing the platinum alloy catalyst, the heat treatment step (2) is as follows: heat treatment is performed at 900°C for 4 hours, and heat treatment at 300°C is not performed, and the other steps remain unchanged.

[0099] Example 6

[0100] This embodiment provides a platinum alloy catalyst, which differs from Example 1 only in that, when preparing the platinum alloy catalyst, the calcination temperature in step (3) is adjusted to 500° C., and the other steps remain unchanged.

[0101] Example 7

[0102] This embodiment provides a platinum alloy catalyst, which differs from embodiment 1 only in that, when preparing the platinum alloy catalyst, the calcination temperature in step (3) is adjusted to 1000° C., and the other steps remain unchanged.

[0103] Comparative Example 1

[0104] This comparative example provides a platinum alloy catalyst, which differs from Example 1 only in that, when preparing the platinum alloy catalyst, steps (1) and (2) are not performed, and the nitrogen-modified ketjen EC300J used in step (3) is replaced with an equal amount of ketjen EC300J, that is, the carbon support is not nitrogen-modified, and the remaining steps remain unchanged.

[0105] Comparative Example 2

[0106] This comparative example provides a commercial platinum-carbon catalyst with a platinum content of 20%.

[0107] Comparative Example 3

[0108] This comparative example provides a commercial platinum-carbon catalyst with a platinum content of 40%.

[0109] Comparative Example 4

[0110] This comparative example provides a commercial platinum-carbon catalyst with a platinum content of 50%.

[0111] Comparative Example 5

[0112] This comparative example provides a commercial platinum-nickel catalyst with a platinum content of 45%.

[0113] Comparative Example 6

[0114] This comparative example provides a commercial platinum-cobalt catalyst with a platinum content of 46.3%.

[0115] Test method: The platinum alloy catalysts prepared in the examples and comparative examples were tested on a rotating disk electrode. 6 mg of catalyst was weighed on a balance and placed in a volumetric flask. 500 μL of water, 1500 μL of isopropanol, and 15 μL of nafion solution (5 wt%) were added with a pipette. The prepared mixture was placed in an ultrasonic instrument for ultrasonic dispersion. The ultrasonic duration was controlled to be 30 minutes each time, and the ultrasonic temperature was controlled at 0°C-5°C until the ultrasonic dispersion was uniform. The slurry was added dropwise to the surface of the glassy carbon electrode with a pipette (one-time addition), and the test electrode preparation was completed after the slurry was dried. The platinum loading on the surface of the glassy carbon electrode head is 20 ug / cm 2 The test results are shown in Table 1 below.

[0116] Table 1

[0117]

[0118]

[0119] The test results show that:

[0120] (1) It can be seen from Examples 1 to 3 that the nitrogen-modified carbon support in the platinum alloy catalyst provided by the present invention enables the platinum alloy to form a coordination bond with the carbon and nitrogen on the support, thereby firmly anchoring the platinum alloy on the carbon support. This breaks through the bottleneck of the weak binding force of commercial catalyst platinum reduction and attachment to the carbon support and the increase in Oswald ripening platinum particle size resulting in poor catalyst durability. It essentially changes the weak interaction mode of traditional catalysts that only relies on physical adsorption. This strong chemical bonding effect effectively inhibits the platinum atom migration and particle coarsening caused by the ripening effect during the electrochemical cycle, thereby improving the electrochemical activity and durability of the catalyst.

[0121] (2) By comparing Example 1 with Examples 4-5, it can be seen that the present invention introduces nitrogen elements on the surface of the carbon support by adopting a two-step heat treatment method. If only a one-step heat treatment is used, the nitrogen atoms cannot be more orderly and effectively incorporated into the gradually formed carbon structure, the nitrogen doping amount and the nitrogen retention rate further decrease, and an intermediate stable structure cannot be formed.

[0122] (3) By comparing Example 1 with Examples 6-7, it can be seen that the present invention further controls the calcination temperature to 600°C-900°C. During this process, platinum and nickel are alloyed in an inert atmosphere. If the calcination temperature is too high, small particles will fuse into large particles, which will reduce the specific surface area and activity.

[0123] (4) It can be seen from Example 1 and Comparative Example 1 that the present invention improves the electrochemical activity and durability of the catalyst by nitrogen modification of the carbon support.

[0124] (5) It can be seen from Example 1 and Comparative Examples 2 to 4, Example 2 and Comparative Example 5, and Example 3 and Comparative Example 6 that the nitrogen-modified carbon support forms a coordination bond between the platinum alloy and the carbon and nitrogen on the support, thereby firmly anchoring the platinum alloy on the carbon support. This breaks through the bottleneck of the weak binding force of the commercial catalyst platinum reduction and adhesion to the carbon support and the increase in the particle size of Oswald-ripened platinum, which leads to poor catalyst durability, and significantly improves the electrochemical activity and durability of the catalyst.

[0125] In summary, the nitrogen-modified carbon support in the platinum alloy catalyst provided by the present invention enables the platinum alloy to form coordination bonds with the carbon and nitrogen on the support, thereby firmly anchoring the platinum alloy on the carbon support. This breaks through the bottleneck of weak binding force of commercial catalyst platinum reduction and adhesion to the carbon support and the increase in Oswald ripening platinum particle size resulting in poor catalyst durability. It fundamentally changes the weak interaction mode of traditional catalysts that only relies on physical adsorption. This strong chemical bonding effect effectively suppresses the platinum atom migration and particle coarsening caused by the ripening effect during the electrochemical cycle, thereby improving the electrochemical activity and durability of the catalyst.

[0126] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A platinum alloy catalyst, characterized in that The platinum alloy catalyst includes a nitrogen-modified carbon support and an active component loaded on the nitrogen-modified carbon support, wherein the active component includes a platinum alloy; the platinum alloy includes a platinum-nickel alloy and / or a platinum-cobalt alloy; and the surface of the nitrogen-modified carbon support contains pyridinic nitrogen and / or pyrrolic nitrogen.

2. The platinum alloy catalyst according to claim 1, characterized in that The platinum loading in the platinum alloy catalyst is 20 wt% to 50 wt%.

3. The platinum alloy catalyst according to claim 1, characterized in that The nitrogen-modified carbon support was prepared by the following method: The carbon support is mixed with mixed acid for pre-oxidation to obtain a pre-oxidized carbon support; and the pre-oxidized carbon support is heat-treated in an atmosphere of ammonia and argon to obtain a nitrogen-modified carbon support.

4. The platinum nickel catalyst according to claim 3, characterized in that The volume ratio of the carbon support to the mixed acid is 1:(5-50); The carbon support comprises any one of ketjen EC300J, ketjen EC600J or carbon nanotubes or a combination of at least two thereof; Preferably, the mixed acid comprises sulfuric acid and nitric acid; Preferably, the volume ratio of the sulfuric acid to the nitric acid is (2-4):

1.

5. The platinum alloy catalyst according to claim 3 or 4, characterized in that The pre-oxidation temperature is 70°C-90°C; Preferably, the pre-oxidation time is 3h-6h; Preferably, the volume ratio of ammonia to argon is (90-95):(5-10); Preferably, the heat treatment includes a first heat treatment and a second heat treatment; Preferably, the temperature of the first heat treatment is 300°C-500°C; Preferably, the first step of heat treatment lasts for 1 hour to 3 hours; Preferably, the temperature of the second heat treatment is 700°C-900°C; Preferably, the second step heat treatment time is 1h-3h; Preferably, after the heat treatment and before obtaining the nitrogen-modified carbon support, acid washing and drying are further performed.

6. A method for preparing a platinum alloy catalyst according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: The carbon support is mixed with a mixed acid for pre-oxidation to obtain a pre-oxidized carbon support; the pre-oxidized carbon support is heat-treated in an atmosphere of ammonia and argon to obtain a nitrogen-modified carbon support; A nitrogen-modified carbon support, a platinum source solution and a transition metal source solution are mixed, reacted and calcined to obtain a platinum alloy catalyst.

7. The preparation method according to claim 6, characterized in that The platinum source includes any one of chloroplatinic acid, platinum nitrate, platinum sulfate, ammonium chloroplatinate or platinum dichloride, or a combination of at least two thereof; Preferably, the transition metal source comprises a nickel source and / or a cobalt source; Preferably, the nickel source comprises any one of nickel chloride, nickel nitrate or nickel sulfate, or a combination of at least two thereof; Preferably, the cobalt source comprises any one of cobalt chloride, cobalt nitrate or cobalt sulfate, or a combination of at least two thereof; Preferably, the molar ratio of platinum ions to transition metal ions in the platinum source solution and the transition metal source solution is 1:(0.3-1); Preferably, the reaction temperature is 70°C-80°C; Preferably, the reaction time is 10h-20h; Preferably, solid-liquid separation and drying treatment are further performed after the reaction and before calcination.

8. The preparation method according to claim 6 or 7, characterized in that The calcination temperature is 600°C-900°C; Preferably, the calcination atmosphere is an inert gas; Preferably, the inert gas comprises argon and hydrogen; Preferably, the volume ratio of argon to hydrogen is (90-95):(5-10); Preferably, the calcination time is 3h-6h.

9. The preparation method according to any one of claims 6 to 8, characterized in that The preparation method comprises the following steps: (1) mixing the carbon support with a mixed acid of sulfuric acid and nitric acid in a volume ratio of (2-4):1 at a carbon support to mixed acid volume ratio of 1:(5-50), and pre-oxidizing at 70°C-90°C for 3h-6h to obtain a pre-oxidized carbon support; (2) heat treating the pre-oxidized carbon support in an atmosphere with a volume ratio of ammonia to argon of (60-90):(10-40), wherein the heat treatment steps are as follows: a first heat treatment at 300°C-500°C for 1h-3h, and then a second heat treatment at 700°C-900°C for 1h-3h, followed by washing with nitric acid and water until neutral, and then drying at 50°C-70°C for 5h-10h to obtain a nitrogen-modified carbon support; (3) mixing a nitrogen-modified carbon support, chloroplatinic acid, and a transition metal source solution, stirring and reacting at 70°C-80°C for 10h-20h, filtering, drying at 50°C-80°C for 5h-10h, and calcining at 600°C-900°C for 3h-6h in an atmosphere of argon and hydrogen with a volume ratio of (90-95):(5-10), acid washing, and drying to obtain a platinum alloy catalyst; The molar ratio of platinum ions to transition metal ions in the platinum source solution and the transition metal source solution is 1:(0.3-1).

10. A fuel cell, characterized in that: The fuel cell comprises the platinum alloy catalyst according to any one of claims 1 to 5 or the platinum alloy catalyst prepared by the preparation method according to any one of claims 6 to 9.

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