Platinum or platinum alloy supported carbon catalyst and its manufacturing method, membrane electrode assembly for polymer electrolyte fuel cell using platinum or platinum alloy supported carbon catalyst, and polymer electrolyte fuel cell

Abstract

To provide a platinum or platinum alloy supported carbon catalyst for a highly active and highly durable solid polymer type fuel cell.SOLUTION: There is provided a platinum or platinum alloy supported carbon catalyst supported by platinum or platinum alloy particles carried on mesoporous carbon, where the support ratio of platinum or platinum alloy in the catalyst is between 30% and 70% by weight relative to total weight of the catalyst, and the total weight of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon accounts for 60% to 90% of the total weight of the platinum particles or platinum alloy particles. The average particle diameter D1 of the platinum particles or platinum alloy particles supported inside the pores of the mesoporous carbon is equal to or larger than the average particle diameter D2 of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon, with both average diameters D1 and D2 independently being between 2 nm and 8 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a highly active and highly durable platinum or platinum alloy supported carbon catalyst for polymer electrolyte fuel cells, in which platinum particles or platinum alloy particles are supported inside and outside the pores of a carrier. [Background technology]

[0002] In recent years, decarbonization and carbon neutrality have been promoted as measures to address energy and environmental issues, and the use of hydrogen as a clean energy alternative to chemical fuels has been attracting attention. Fuel cells generate electricity through a chemical reaction between hydrogen and oxygen, and because they do not emit carbon dioxide, a greenhouse gas, they are expected to be a new power generation system that contributes to carbon neutrality. One type of fuel cell, the polymer electrolyte fuel cell (PEFC), uses a solid polymer ion-conducting membrane as the electrolyte layer. Its operating temperature is low, ranging from room temperature to 100°C, and it can be miniaturized, so its practical use as a power source for electric vehicles and stationary power sources is being promoted.

[0003] A polymer electrolyte fuel cell has a cell stack structure in which multiple single cells, each with a membrane electrode assembly (MEA) sandwiched between separators, are stacked. The MEA has a structure in which an electrolyte layer is sandwiched between two electrode catalyst layers made of an electrode catalyst and an electrolyte polymer (ionomer).

[0004] In the MEA, the following electrochemical reactions take place to generate electricity. First, hydrogen supplied as fuel is oxidized by an electrode catalyst in the fuel electrode (anode) electrode catalyst layer, generating protons and electrons. Next, the generated protons pass through an electrolyte layer made of an ion-conductive electrolyte, while the electrons pass through an external circuit to reach the oxygen electrode (cathode) electrode catalyst layer. The protons and electrons that reach the cathode electrode catalyst layer react with oxygen supplied to the cathode side to generate water. The electrons generated at the anode are used as electrical energy as they travel to the cathode electrode via the external circuit.

[0005] Conventional electrode catalysts use platinum or platinum alloy-supported carbon catalysts, which are made by supporting nanoparticles of platinum (Pt) or platinum alloys on a highly electron-conductive carbon black support. These platinum or platinum alloy-supported carbon catalysts use high-specific-surface-area carbon to support platinum particles or platinum alloy particles in a highly dispersed state without agglomeration. This increases the electrode reaction area on the surface of the platinum or platinum alloy particles, enabling sufficient activity with a small amount of platinum or platinum alloy supported.

[0006] In order to popularize fuel cell vehicles (FCVs) toward achieving carbon neutrality, there is a need to develop cathode catalysts for polymer electrolyte fuel cells (PEFCs) that are highly efficient and capable of high-load operation.

[0007] Cited Document 1 describes a platinum-supported carbon catalyst supported on solid-structure carbon such as furnace black or acetylene black, which has dense particles inside.

[0008] Cited Document 2 discloses an electrode catalyst in which platinum particles are supported within the pores of a porous hollow carbon support such as Ketjenblack. It mentions that by supporting platinum particles within the pores, adsorption of ionomer onto the platinum particle surface can be suppressed, preventing a decrease in the effective reaction surface area of ​​the platinum particles. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-112660 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-109856 Summary of the Invention [Problem to be solved by the invention]

[0010] For example, platinum-supported carbon catalysts supported on solid-structure carbon, such as furnace black or acetylene black, have excellent mass transport properties because the platinum particles are supported on the surface of the support, and the reaction progresses easily when the reactant gas comes into contact with the platinum particles. However, because the platinum particles are on the surface of the support, there are problems with reduced activity due to ionomer poisoning and catalyst deterioration due to platinum particle aggregation (sintering).

[0011] On the other hand, platinum-supported carbon catalysts, which use porous carbon such as Ketjenblack as a support and have platinum particles supported within the pores, are also widely used. Because the platinum particles are supported within the pores of the support, ionomer poisoning is reduced and a decrease in catalytic activity is suppressed. However, while platinum particles supported within the pores have high activity, there is a problem in that access of protons and reactant gases is limited.

[0012] Therefore, there is a need for a method for loading platinum particles or platinum alloy particles inside and outside the pores of a carrier at any ratio. Furthermore, if platinum particles or platinum alloy particles can be loaded inside and outside the pores of a carrier at any ratio, it will be possible to provide catalytically active components with different functions by selectively loading them inside and outside the pores, thereby adjusting performance.

[0013] An object of the present invention is to provide a platinum or platinum alloy supported carbon catalyst that has high initial activity and excellent durability by selectively supporting platinum particles or platinum alloy particles inside and outside the pores of a carbon support. [Means for solving the problem]

[0014] The inventors have discovered that by adopting a two-stage loading process, which involves a step of loading platinum particles or platinum alloy particles inside the pores of a carbon support by impregnation, and a step of loading platinum particles outside the pores of the carbon support by liquid-phase reduction, it is possible to control the loading amount and particle size of the platinum particles or platinum alloy particles loaded inside and outside the pores.

[0015] That is, the present invention is A platinum or platinum alloy-supported carbon catalyst in which platinum particles or platinum alloy particles are supported on mesoporous carbon, The platinum or platinum alloy loading rate in the catalyst is 30% to 70% by weight based on the total weight of the catalyst, the total weight of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon is 60 to 90% of the total weight of the platinum particles or platinum alloy particles; the average particle size D1 of the platinum particles or platinum alloy particles supported within the pores of the mesoporous carbon is equal to or larger than the average particle size D2 of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon; The average particle size D1 and the average particle size D2 are independently 2 nm or more and 8 nm or less. The present invention relates to a platinum or platinum alloy supported carbon catalyst.

[0016] In the above configuration, the average particle size D1 is 2.5 nm or more and 8 nm or less, the average particle size D2 is 2.3 nm or more and 7.3 nm or less, D1 / D2 may be set to be 1.0 to 2.1.

[0017] Further, the manufacturing method of the present invention includes the steps of: a step of impregnating a mesoporous carbon support with an aqueous solution containing a platinum compound; a step of drying the mesoporous carbon support impregnated with the platinum compound-containing aqueous solution obtained in the above step under reduced pressure; an intra-pore supporting step of supporting platinum in the pores of the mesoporous carbon support, the intra-pore supporting step including a step of heat-treating the mesoporous carbon support obtained in the reduced pressure drying step in a reducing atmosphere; a step of suspending the mesoporous carbon support having platinum supported in the pores after the intrapore supporting step in an aqueous solution; an outside-pore supporting step of supporting platinum particles outside the pores of the mesoporous carbon support, the outside-pore supporting step including a step of mixing the suspension with a platinum compound-containing aqueous solution and a liquid containing a reducing agent to reduce the platinum compound; The present invention relates to a method for producing a platinum-supported carbon catalyst, comprising the steps of:

[0018] The in-pore supporting step includes: a step of adding and mixing an aqueous solution of dinitrodiamine platinum nitric acid to a mesoporous carbon support to obtain a platinum-supported carbon slurry; a step of drying the obtained slurry under reduced pressure at a predetermined temperature to obtain a dry solid; a step of reducing dinitrodiammine platinum by heat treatment in a reducing atmosphere; and a step of growing platinum particles by firing in an inert gas atmosphere (firing temperature T1), The outside-pore supporting step includes: The mesoporous carbon support having platinum supported in the pores after the intrapore supporting step is suspended in an aqueous nitric acid solution; a step of heating and stirring the suspension, an aqueous solution of dinitrodiamine platinum nitrate, and a liquid containing L-ascorbic acid at 80°C to 100°C for 30 minutes to 5 hours to support platinum particles outside the pores of the carbon support; a step of filtering out the platinum-supported carbon in which platinum particles are supported outside the pores of the carbon support in the above step, washing it, drying it, and then firing it in an inert gas atmosphere (firing temperature T2) to grow platinum particles; The above may be included.

[0019] In the above manufacturing method, a step of adding an aqueous solution containing a compound of a metal to be alloyed with the platinum to the platinum-supported carbon catalyst and mixing them to obtain a slurry; and a step of heating and drying the obtained slurry under reduced pressure to obtain a dry solid. The method may further include an alloying step of performing a pre-treatment firing of the dried product in a reducing atmosphere, followed by firing in an inert gas atmosphere to perform an alloying treatment.

[0020] In the above manufacturing method, The average particle diameter D1 of the platinum particles and the average particle diameter D2 of the platinum particles may be controlled by setting the firing temperature T1 and the firing temperature T2 to predetermined temperatures, respectively. [Effects of the Invention]

[0021] According to the present invention, by selectively supporting platinum particles or platinum alloy particles inside and outside the pores of a carbon support, it is possible to provide a platinum or platinum alloy-supported carbon catalyst that has high initial activity and excellent durability. DETAILED DESCRIPTION OF THE INVENTION

[0022] First, the manufacturing method of the present invention will be explained.

[0023] The manufacturing method of the present invention comprises: a step of impregnating a mesoporous carbon support with an aqueous solution containing a platinum compound; a step of drying the mesoporous carbon support impregnated with the platinum compound-containing aqueous solution obtained in the above step under reduced pressure; an intra-pore supporting step of supporting platinum in the pores of the mesoporous carbon support, the intra-pore supporting step including a step of heat-treating the mesoporous carbon support obtained in the reduced pressure drying step in a reducing atmosphere; a step of suspending the mesoporous carbon support having platinum supported in the pores after the intrapore supporting step in an aqueous solution; an outside-pore supporting step of supporting platinum particles outside the pores of the mesoporous carbon support, the outside-pore supporting step including a step of mixing the suspension with a platinum compound-containing aqueous solution and a liquid containing a reducing agent to reduce the platinum compound; The present invention relates to a method for producing a platinum-supported carbon catalyst, comprising the steps of:

[0024] Further, the manufacturing method of the present invention includes the steps of: In the above manufacturing method, The in-pore supporting step includes: a step of adding and mixing an aqueous solution of dinitrodiamine platinum nitric acid to a mesoporous carbon support to obtain a platinum-supported carbon slurry; a step of drying the obtained slurry under reduced pressure at a predetermined temperature to obtain a dry solid; a step of reducing dinitrodiammine platinum by heat treatment in a reducing atmosphere; and a step of growing platinum particles by firing in an inert gas atmosphere (firing temperature T1), The outside-pore supporting step includes: The mesoporous carbon support having platinum supported in the pores after the intrapore supporting step is suspended in an aqueous nitric acid solution; a step of heating and stirring the suspension, an aqueous solution of dinitrodiamine platinum nitrate, and a liquid containing L-ascorbic acid at 80°C to 100°C for 30 minutes to 5 hours to support platinum particles outside the pores of the carbon support; a step of filtering out the platinum-supported carbon in which platinum particles are supported outside the pores of the carbon support in the above step, washing it, drying it, and then firing it in an inert gas atmosphere (firing temperature T2) to grow platinum particles; The above may be included.

[0025] When a catalytically active component (e.g., platinum) is supplied in a solution and supported on a support, this is called impregnation, and the catalytically active component (e.g., platinum) is likely to be supported in the pores of the support. The production method of the present invention employs a two-stage support process in which the catalytically active component (e.g., platinum) is supported in the pores of the support by impregnation, and then the catalytically active component (e.g., platinum) is supported outside the pores of the support by liquid-phase reduction.

[0026] As the platinum-containing aqueous solution, a dinitrodiamine platinum nitric acid aqueous solution, a chloroplatinic acid aqueous solution, or the like can be used.

[0027] Mesoporous carbon is used as the support. Mesoporous carbon is a carbon material with nanometer-order pores. Mesoporous carbon with various pore volumes and specific surface areas can be used for the platinum or platinum alloy-supported carbon catalyst of the present invention.

[0028] In the outer pore loading step, L-ascorbic acid, citric acid, etc. are used as reducing agents. In the outside-pore supporting step, an alcohol-based solvent may be added to the aqueous nitric acid solution as a dispersion solvent. Examples of the alcohol-based solvent that can be used include ethanol and 2-propanol.

[0029] The inert gas may be nitrogen, argon, or the like.

[0030] Hereinafter, the platinum particles or platinum alloy particles supported within the pores of the carrier will be referred to as first platinum particles or platinum alloy particles, and the platinum particles or platinum alloy particles supported outside the pores of the carrier will be referred to as second platinum particles or platinum alloy particles.

[0031] The process for supporting platinum in the pores of a mesoporous carbon support is, for example, as follows: A dinitrodiamine platinum nitric acid aqueous solution is added to and mixed with the mesoporous carbon support to form a platinum-supported carbon slurry, which is then dried under reduced pressure at a predetermined temperature to obtain a dried product. The resulting dried product is heat-treated in a reducing atmosphere to reduce the dinitrodiamine platinum, and then calcined in an inert gas (e.g., nitrogen) atmosphere (calcination temperature T1) to grow platinum particles, producing carbon with first platinum particles supported within the pores.

[0032] The outside-pore supporting step is, for example, as follows: The carbon carrying the first platinum particles within the pores is suspended in an aqueous nitric acid solution, and the suspension is mixed with an aqueous dinitrodiamine platinum nitric acid solution, ethanol, and L-ascorbic acid. Next, the mixture is heated and stirred at 80°C to 100°C for 30 minutes to 5 hours. For example, the mixture is heated at 90°C for 1 hour using a reflux reactor to reduce the dinitrodiamine platinum in the liquid phase, and platinum particles are supported outside the pores of the carbon support. The platinum-supported carbon, which has second platinum particles supported outside the pores of the carbon support, is filtered out, then washed and dried, and then calcined in an inert gas atmosphere (calcination temperature T2) to grow the platinum particles, thereby preparing a platinum-supported carbon catalyst in which platinum particles are selectively supported inside and outside the pores of the carbon support.

[0033] After the above-mentioned filtration, washing, and drying, but before calcination in an inert gas atmosphere (calcination temperature T2), any remaining residue of the reducing agent (L-ascorbic acid) that was not removed by washing may be thermally decomposed and removed by heat treatment in an oxygen-free atmosphere, such as a 4.0% hydrogen / nitrogen atmosphere.

[0034] The production method of the present invention includes the steps of: adding an aqueous solution containing a compound of a metal to be alloyed with the platinum to the platinum-supported carbon catalyst and mixing them to obtain a slurry; and heating and drying the obtained slurry under reduced pressure to obtain a dry product. The method may further include an alloying step of performing a pre-treatment firing of the dried product in a reducing atmosphere, followed by firing in an inert gas atmosphere to perform an alloying treatment.

[0035] For example, a cobalt nitrate solution prepared by dissolving cobalt(II) nitrate hexahydrate in water is added to the platinum-supported carbon catalyst prepared by the above method, and the mixture is mixed using a kneader to obtain a slurry. The resulting slurry is dried using a vacuum dryer, for example, at 80°C to 250°C under reduced pressure for 1 to 15 hours to obtain a dried product. This dried product is reduced in an atmosphere furnace in a hydrogen / nitrogen mixed atmosphere at 200°C to 600°C for 1 to 5 hours, and then calcined in an inert gas flow at 700°C to 900°C for 0.5 to 5 hours to perform an alloying treatment. The excess cobalt is then removed by acid washing. The product is then filtered, washed, and dried to obtain a platinum-cobalt-supported carbon catalyst.

[0036] In addition, in the manufacturing method of the present invention, the average particle diameter D1 of the platinum particles and the average particle diameter D2 of the platinum particles may be controlled by setting the firing temperature T1 and the firing temperature T2 to predetermined temperatures, respectively.

[0037] The firing temperature T1 and the firing temperature T2 can be set, for example, to 500° C. to 1000° C. By firing at 500° C. to 1000° C., the platinum particles can be formed to a predetermined size.

[0038] Next, the catalyst of the present invention is A platinum or platinum alloy-supported carbon catalyst in which platinum particles or platinum alloy particles are supported on mesoporous carbon, The platinum or platinum alloy loading rate in the catalyst is 30% to 70% by weight based on the total weight of the catalyst, the total weight of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon is 60 to 90% of the total weight of the platinum particles or platinum alloy particles; the average particle size D1 of the platinum particles or platinum alloy particles supported within the pores of the mesoporous carbon is equal to or larger than the average particle size D2 of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon; The average particle size D1 and the average particle size D2 are independently 2 nm or more and 8 nm or less. The present invention relates to a platinum or platinum alloy supported carbon catalyst.

[0039] The platinum or platinum alloy loading rate in the platinum or platinum alloy-supported carbon catalyst can be determined, for example, by using aqua regia to dissolve the metal components contained in the platinum particles or platinum alloy particles from the platinum or platinum alloy-supported carbon catalyst, and then quantifying the metal ions in the solution using an inductively coupled plasma (ICP) optical emission spectrometer.

[0040] The platinum or platinum alloy loading rate in the platinum or platinum alloy-supported carbon catalyst is 30% to 70% by weight of the total weight of the catalyst. By ensuring that the loading density of platinum particles or platinum alloy particles is within this range, the thickness of the electrode catalyst layer can be controlled to be suitable for proton transfer, gas diffusion, and drainage of generated water during the formation of the electrode catalyst layer.

[0041] The platinum or platinum alloy loading ratio in the platinum or platinum alloy supported carbon catalyst is preferably 35% to 60% by weight based on the total weight of the catalyst, and more preferably 40% to 55% by weight based on the total weight of the catalyst.

[0042] The total weight of platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon is 60 to 90% of the total weight of platinum particles or platinum alloy particles supported on the mesoporous carbon (i.e., the total weight of platinum particles or platinum alloy particles supported inside and outside the pores of the mesoporous carbon). Supporting platinum particles or platinum alloy particles inside the pores of the carbon support reduces the contact area with the ionomer, thereby reducing poisoning of the platinum particles or platinum alloy particles by the sulfonic acid groups of the ionomer and expected to demonstrate high initial activity. However, from the perspective of mass transport properties such as protons and reactant gases, the ratio of the particles supported inside the pores to the particles outside the pores must be appropriately adjusted. Therefore, the total weight of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon is set to 60 to 90% of the total weight of platinum particles or platinum alloy particles supported on the mesoporous carbon.

[0043] The total weight of platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon is preferably 80% or less, and more preferably 70% or less, of the total weight of platinum particles or platinum alloy particles supported on the mesoporous carbon.

[0044] The catalyst of the present invention is The average particle size D1 of the platinum particles or platinum alloy particles is 2.5 nm or more and 8 nm or less, The average particle size D2 of the platinum particles or platinum alloy particles is 2.3 nm or more and 7.3 nm or less. , D1 / D2 is 1.0 to 2.1. This may be done.

[0045] In a fuel cell operating environment accompanied by potential fluctuations, small platinum particles preferentially dissolve and are redeposited on the surfaces of larger platinum particles, resulting in coarsening of the platinum particles and degradation of the catalytically active components. To prevent platinum or platinum alloy particles supported within the pores, which are resistant to ionomer poisoning and exhibit high activity, from leaching out of the pores, it is preferable that the average particle size D1 be greater than or equal to the average particle size D2. Here, the average particle size D1 is the average particle size of platinum or platinum alloy particles supported within the pores of the mesoporous carbon, and the average particle size D2 is the average particle size of platinum or platinum alloy particles supported outside the pores.

[0046] It is more preferable that the average particle size D1 of the platinum particles or platinum alloy particles (platinum particles or platinum alloy particles inside the pores) is larger than the average particle size D2 of the platinum particles or platinum alloy particles (platinum particles or platinum alloy particles outside the pores).

[0047] D1 / D2 can be set to 1.0 to 2.1, and is preferably set to 1.1 to 1.8.

[0048] By having the average particle size of the platinum particles or platinum alloy particles within the above range, both initial activity and durability can be achieved. If the average particle size of the platinum particles or platinum alloy particles is smaller than the above range, the active surface area will be larger and initial activity will be improved, but coarsening due to dissolution and redeposition of the platinum particles or platinum alloy particles will be more likely to occur, resulting in reduced durability. On the other hand, if the average particle size of the platinum particles or platinum alloy particles is larger than the above range, coarsening due to dissolution and redeposition and migration and aggregation of the platinum particles or platinum alloy particles will be less likely to occur, but the initial activity will be reduced due to the low active surface area of ​​the platinum particles or platinum alloy particles.

[0049] By selectively supporting platinum particles or platinum alloy particles supported inside the pores, which suppress ionomer poisoning and exhibit high activity, and platinum particles or platinum alloy particles supported outside the pores, which have excellent mass transport properties, performance can be adjusted to exhibit high initial activity. Furthermore, by making the average particle size of the platinum particles or platinum alloy particles supported inside the pores larger than that of the platinum particles or platinum alloy particles supported outside the pores, deterioration due to elution of the platinum particles or platinum alloy particles under operating conditions is suppressed, thereby improving durability.

[0050] The catalytically active component contained in the platinum or platinum alloy supported carbon catalyst of the present invention is platinum (Pt) or a platinum alloy. One or more additional metals forming the platinum alloy in the platinum alloy can include titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), yttrium (Y), zirconium (Zr), molybdenum (Mo), lanthanum (La), cerium (Ce), gadolinium (Gd), hafnium (Hf), tantalum (Ta), ruthenium (Ru), iridium (Ir), palladium (Pd), osmium (Os), and rhodium (Rh). When the platinum alloy particles contained in the fuel cell electrode catalyst of the present invention contain the above catalytic metals, an electrode catalyst with high activity and high durability can be obtained. [Example]

[0051] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0052] Example 1 1. Preparation of carbon with platinum supported in pores (first platinum particle support step in pores) As a support, pore volume 3.5 cm 3 / g mesoporous carbon was used. 128.0 g of dinitrodiamine platinum nitric acid aqueous solution containing 8.3 wt% platinum was added to 31.8 g of mesoporous carbon support, and the mixture was mixed for 30 minutes using a kneader to obtain a platinum-supported carbon slurry. The resulting slurry was dried under reduced pressure at 200°C for 12 hours using a vacuum dryer to obtain a dried product. The dried product was then heat-treated in an atmospheric furnace at 200°C for 2 hours under a 4.0% hydrogen / nitrogen flow to reduce the dinitrodiamine platinum. The mixture was then calcined for 1 hour at a calcination temperature T1 (medium) of 600°C under a nitrogen flow to grow platinum particles, resulting in carbon with 25 wt% of first platinum particles supported within the pores.

[0053] 2. Preparation of carbon catalyst with platinum supported inside and outside the pores (second platinum particle supporting step outside the pores) 10.0 g of carbon carrying 25 wt% of first platinum particles within the pores was suspended in 150 g of 0.1 M nitric acid, to which 48.1 g of dinitrodiamine platinum nitric acid aqueous solution containing 8.3 wt% platinum, 4.0 g of ethanol, and 7.5 g of L-ascorbic acid were added to form a mixture. This mixture was heated at 90°C for 1 hour using a reflux reactor to reduce the dinitrodiamine platinum in the liquid phase, and platinum particles were supported outside the pores of the carbon support. Next, the mixture was allowed to cool to room temperature, and the platinum-supported carbon in the mixture was filtered off, washed, and dried at 60° C. for 12 hours. After drying, the substrate was heat-treated in an atmospheric furnace under a 4.0% hydrogen / nitrogen flow at 200°C for 2 hours to thermally decompose the adhering reducing agent (L-ascorbic acid) residue. Next, the mixture was fired at a firing temperature T2 (outside) of 600° C. under a nitrogen flow for 1 hour to grow platinum particles supported outside the pores. As a result, a carbon catalyst was obtained in which 47 wt% of platinum 1 and 2 particles were supported inside and outside the pores. The total weight of the platinum 2 particles supported outside the pores of the mesoporous carbon was 63% of the total weight of the platinum 1 and 2 particles supported on the mesoporous carbon.

[0054] Example 2 A platinum-supported carbon catalyst was obtained in the same manner as in Example 1, except that the nitrogen calcination temperature T1 (medium) in the step of supporting the first platinum particles in the pores was changed from 600°C to 700°C.

[0055] Example 3 A platinum-supported carbon catalyst was obtained in the same manner as in Example 1, except that the nitrogen calcination temperature T1 (medium) in the step of supporting the first platinum particles in the pores was changed from 600°C to 900°C.

[0056] Example 4 A platinum-supported carbon catalyst was obtained in the same manner as in Example 1, except that the nitrogen calcination temperature T1 (medium) in the step of supporting the first platinum particles in the pores was changed from 600°C to 1000°C.

[0057] Example 5 The carrier used had a pore volume of 4.5 cm 3 A platinum-supported carbon catalyst was obtained in the same manner as in Example 1, except that the catalyst was changed to mesoporous carbon with a catalyst content of 1000 ppm or more and a catalyst content of 1000 ppm or less.

[0058] Example 6 To 5.02 g of the carbon catalyst supporting the intra- and extra-pore platinum of Example 1, an aqueous solution of cobalt nitrate prepared by dissolving 2.48 g of cobalt (II) nitrate hexahydrate in 5.18 g of water was added, and the mixture was mixed for 30 minutes using a kneader to obtain a slurry. The resulting slurry was dried under reduced pressure at 200°C for 12 hours using a vacuum dryer to obtain a dried product. This dried product was reduced in an atmospheric furnace at 200°C for 2 hours under a 4.0% hydrogen / nitrogen flow, and then calcined at 800°C for 1 hour under a nitrogen flow to perform an alloying treatment. To remove excess cobalt by acid washing, 80 g of 1M nitric acid was added, and the mixture was heated at 90°C for 1 hour. After cooling to room temperature, the black powder was filtered, washed, and dried at 80°C for 12 hours. As a result, 5.28 g of a platinum-cobalt supported carbon catalyst was obtained.

[0059] (Comparative Example 1) Pore ​​volume 3.5cm 354.2 g of dinitrodiamine platinum nitric acid aqueous solution containing 8.3 wt% platinum was added to 10.0 g of mesoporous carbon support (10.0 g / g), and the mixture was mixed for 30 minutes using a kneader to obtain a platinum-supported carbon slurry. The resulting slurry was dried under reduced pressure at 200°C for 12 hours using a vacuum dryer to obtain a dried product. The dried product was then heat-treated in an atmospheric furnace at 200°C for 2 hours under a 4.0% hydrogen / nitrogen flow to reduce the dinitrodiamine platinum. It was then calcined at 200°C for 2 hours under a nitrogen flow to grow platinum particles. This resulted in carbon supported with 31 wt% of first platinum particles in the pores. To 12.0 g of this carbon with 31 wt% of first platinum particles supported in the pores, 43.6 g of dinitrodiamine platinum nitric acid aqueous solution containing 8.3 wt% platinum was added again using the same procedure, and the mixture was kneaded, dried, subjected to reduction heat treatment, and fired to obtain a carbon catalyst with 47 wt% of first platinum particles supported in the pores.

[0060] (Comparative Example 2) Pore ​​volume 3.5cm 3 10.0 g of mesoporous carbon support with a molecular weight of 1 / g was suspended in 400 g of 0.1 M nitric acid, to which 106.6 g of dinitrodiamine platinum nitric acid solution containing 8.3 wt% platinum, 10.3 g of ethanol, and 16.0 g of L-ascorbic acid were added to form a mixture. This mixture was heated at 90°C for 1 hour in a reflux reactor to reduce the dinitrodiamine platinum in the liquid phase, and platinum particles were supported outside the pores of the carbon support. Next, the mixture was allowed to cool to room temperature, and the platinum-supported carbon in the mixture was filtered off, washed, and dried at 60° C. for 12 hours. After drying, the substrate was heat-treated in an atmospheric furnace under a 4.0% hydrogen / nitrogen flow at 200°C for 2 hours to thermally decompose the adhering reducing agent (L-ascorbic acid) residue. Next, the catalyst was baked at 200°C for 2 hours under a nitrogen flow to grow platinum particles supported outside the pores. As a result, a carbon catalyst was obtained that supported 47 wt% of second platinum particles outside the pores.

[0061] The platinum or platinum alloy supported carbon catalysts of the Examples and Comparative Examples were evaluated for the following physical properties. The results are shown in Table 1.

[0062] [Measurement of particle size distribution of platinum particles or platinum alloy particles in platinum or platinum alloy supported carbon catalysts] The particle size distribution of platinum particles or platinum alloy particles was measured using CuKα radiation as a radiation source and a small angle scattering measurement device (Nano-Viewer manufactured by Rigaku) ​​under the following measurement conditions.

[0063] Small-angle X-ray scattering measurement (SAXS) measurement conditions Tube: CuKα ray Output: 40kV-30mA Slits: 1st slit 0.4mm, 2nd slit 0.2mm, 3rd slit 0.45mm Measurement method: Transmission method Detector: HyPix-3000 Camera length: 680mm Exposure time: 15 minutes Temperature: room temperature

[0064] [Measurement of the metal specific surface area of ​​platinum particles or platinum alloy particles in platinum or platinum alloy supported carbon catalysts] The metal specific surface area of ​​platinum particles or platinum alloy particles is measured using a metal dispersion measurement device (micrometer). Measurements were made using a Rotrak-Bel BELMETAL3) using a pulse method with carbon monoxide gas. The metal specific surface area of ​​the catalyst particles was determined from the amount of carbon monoxide adsorbed.

[0065] [Measurement of BET specific surface area of ​​carbon support for platinum or platinum alloy supported carbon catalyst] BET specific surface area (m 2 For the specific surface area (g), an automatic specific surface area / pore distribution analyzer (Microtrack-Bell BELSORP-mini2) was used to obtain a nitrogen adsorption isotherm by the gas adsorption method using nitrogen gas, and the specific surface area was determined by the multipoint method based on the BET method.

[0066] [Table 1]

[0067] In Example 1, the firing temperatures T1 (middle) and T2 (outside) were both 600°C, and the average particle size D1 of the first platinum particles inside the pores and the average particle size D2 of the second platinum particles outside the pores were 3.5 nm, which were approximately the same size.

[0068] In Examples 2 to 4, the firing temperature T1 (middle) was higher than T2 (outside), and the average particle size D1 of the first platinum particles inside the pores was 3.8 to 7.1 nm, while the average particle size D2 of the second platinum particles outside the pores was 3.4 to 3.5 nm, with the average particle size D1 of the first platinum particles inside the pores being larger.

[0069] Example 5 uses mesoporous carbon with a different pore volume from Examples 1 to 4. As in Example 1, by treating at firing temperatures T1 (middle) and T2 (outside) of 600°C, the average particle size D1 of the first platinum particles inside the pores and the average particle size D2 of the second platinum particles outside the pores were 3.1 nm, which were approximately the same size.

[0070] In Example 6, the platinum-cobalt supported carbon was adjusted so that the average particle size D1 of the first catalyst particles inside the pores and the average particle size D2 of the second catalyst particles outside the pores were 4.4 nm, which were approximately the same size.

[0071] In Comparative Example 1, the platinum-supported carbon catalyst was prepared by repeating the intrapore supporting step by the impregnation method twice. The average particle size D1 of the first platinum particles in the pores was 3.9 nm.

[0072] In Comparative Example 2, a platinum-supported carbon catalyst was prepared by an outside-pore supporting step using a liquid-phase reduction method. The average particle size D2 of the second platinum particles outside the pores was 3.8 nm.

[0073] The metal specific surface area of ​​the examples and comparative examples is 57 to 100 m 2 g -1 The BET specific surface area of ​​the examples and comparative examples was 290 to 630 m 2 g -1 It was.

[0074] For the platinum or platinum alloy supported carbon catalysts of the Examples and Comparative Examples, membrane electrode assemblies for evaluation of single cells of polymer electrolyte fuel cells were fabricated by the following method.

[0075] 1. Electrode Preparation 0.8 g of platinum or platinum alloy-supported carbon catalyst from each example and comparative example, 4.16 g of pure water, 1.60 g of ionomer (Nafion DE2020CS manufactured by Chemours), 2.43 mL of 2-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 1.88 mL of 1-propanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 0.72 mL of propylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed and dispersed in a planetary ball mill for 1 hour and then degassed for 5 minutes in a mixer to prepare a cathode catalyst slurry. This electrode catalyst slurry was applied to one side of a PTFE sheet (Naflon® sheet manufactured by Nichias Corporation, thickness 200 μm) using a doctor blade and dried at 120°C for 60 minutes under vacuum to form a cathode catalyst layer on the PTFE sheet.

[0076] For the anode catalyst layer, FC-I2 (IFPC40-II manufactured by Ishifuku Metal Industries), the reference catalyst of the Catalysis Society of Japan's Fuel Cell Related Catalysts Study Group, was used.

[0077] 2. MEA Fabrication Two previously prepared PTFE sheets with catalyst layers were stacked on top of each other with the catalyst layer side facing inward, sandwiching a solid polymer electrolyte membrane (Chemours Nafion NR-211, 200 mm x 200 mm square). The resulting assembly was hot-pressed at 130°C for 10 minutes at a pressure of 1.5 K / N using a precision heating and pressing device (Shinto Kogyo CYPM). After cooling, the PTFE sheets were peeled off, resulting in a bonded assembly with the catalyst layer transferred to the solid polymer electrolyte membrane. The transfer rate of the catalyst layer from the PTFE sheet to the solid polymer electrolyte membrane was 100%, and the platinum weight per cm2 of the catalyst layer on each side of the solid polymer electrolyte membrane was 0.30 mg.

[0078] Next, the previously prepared assembly was sandwiched between two gas diffusion layers (GDL 28BC manufactured by SGL, 100 mm × 100 mm square), and a sealing material (Naflon (registered trademark) sheet manufactured by Nichias Corporation, laminated with a thickness of 150 μm and a thickness of 80 μm) was placed around the outer periphery of the electrode catalyst layer and the gas diffusion layer to form an MEA.

[0079] Thereafter, a gold-plated current collector with gas flow channels was placed on the fabricated MEA, which was then clamped between stainless steel end plates and tightened to a predetermined surface pressure to obtain a single cell of a polymer electrolyte fuel cell.

[0080] The MEAs using the platinum or platinum alloy supported carbon catalysts of each of the Examples and Comparative Examples were evaluated for power generation as follows. The results are shown in Table 2.

[0081] [Measurement of initial activity of MEA using platinum or platinum alloy supported carbon catalyst] Based on the New Energy and Industrial Technology Development Organization (NEDO)'s "NEDO PEFC Cell Evaluation and Analysis Protocol, March 2022 Edition," IV measurements were performed using a fuel cell power generation evaluation device (manufactured by Chino) and an electronic load device (Kikusui Electronics PLZ164WA). Mass activity was calculated from the current density at 0.85 V and the amount of platinum loaded, and the initial activity was determined.

[0082] [Measurement of durability of MEA using platinum or platinum alloy supported carbon catalyst] Based on the potential cycle (load response) test method described in the New Energy and Industrial Technology Development Organization (NEDO)'s "NEDO PEFC Cell Evaluation and Analysis Protocol, March 2022 Edition," a load response simulated potential cycle test that accelerates the deterioration of platinum particles or platinum alloy particles in a platinum or platinum alloy-supported carbon catalyst was conducted using a fuel cell power generation evaluation device (manufactured by Chino) and a potentiogalvanostat (PGSTAT128N, manufactured by Metrohm).The mass activity after the durability test was calculated from the current density at 0.85 V and the amount of platinum supported after 30,000 cycles, and durability was evaluated.

[0083] At initial activation, 800Ag -1Above: ◎, 300Ag -1 Over 800Ag -1 In terms of activity after durability, 300Ag -1 Above: ◎, 100Ag -1 Over 300Ag -1 Less than 100Ag: 〇 -1 Less than this was evaluated as x.

[0084] [Table 2]

[0085] In Examples 1 to 6, the total weight of the second platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon was adjusted to 60 to 90% of the total weight of the first and second platinum particles or platinum alloy particles supported inside and outside the pores of the mesoporous carbon in two stages. The average particle size D1 of the platinum particles or platinum alloy particles supported inside the pores of the glass carbon is equal to or larger than the average particle size D2 of the platinum particles or platinum alloy particles supported outside the pores, and the initial mass activity is 300 Ag -1 and mass activity after 30,000 cycles is 100Ag -1 The above results indicate that the catalyst had good initial activity and durability.

[0086] Comparative Example 1 is a platinum-supported carbon catalyst prepared by repeating only the intrapore support step twice, and the initial mass activity was 498Ag -1 While the initial activity was good, the mass activity after 30,000 cycles was 52Ag -1 The durability was also low.

[0087] Comparative Example 2 is a platinum-supported carbon catalyst prepared only by the liquid phase reduction method, which is an extra-pore supporting process, and the initial mass activity was 371Ag -1 While the initial activity was good, the mass activity after 30,000 cycles was 47Ag -1 The durability was also low.

Claims

1. A platinum or platinum alloy-supported carbon catalyst in which platinum particles or platinum alloy particles are supported on mesoporous carbon, The platinum or platinum alloy loading rate in the catalyst is 30% to 70% by weight based on the total weight of the catalyst, the total weight of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon is 60 to 90% of the total weight of the platinum particles or platinum alloy particles; the average particle size D1 of the platinum particles or platinum alloy particles supported within the pores of the mesoporous carbon is equal to or larger than the average particle size D2 of the platinum particles or platinum alloy particles supported outside the pores of the mesoporous carbon, and D1 / D2 is 1.0 to 2.1; The average particle size D1 and the average particle size D2 are independently 2 nm or more and 8 nm or less, 1. A platinum or platinum alloy supported carbon catalyst.

2. the average particle size D1 is 2.5 nm or more and 8 nm or less, The average particle size D2 is 2.3 nm or more and 7.3 nm or less.

2. The platinum or platinum alloy supported carbon catalyst according to claim 1.

3. impregnating a mesoporous carbon support with an aqueous solution of dinitrodiamine platinum nitrate; a step of drying the mesoporous carbon support impregnated with the platinum compound-containing aqueous solution obtained in the above step under reduced pressure; an intra-pore supporting step of supporting platinum in the pores of the mesoporous carbon support, the intra-pore supporting step comprising a step of heat-treating the mesoporous carbon support obtained in the vacuum drying step in the presence of L-ascorbic acid; a step of suspending the mesoporous carbon support having platinum supported in the pores after the intrapore supporting step in an aqueous solution; an outside-pore supporting step of supporting platinum particles outside the pores of the mesoporous carbon support, the outside-pore supporting step including a step of mixing the suspension with a platinum compound-containing aqueous solution and a liquid containing a reducing agent to reduce the platinum compound; A method for producing a platinum-supported carbon catalyst, comprising:

4. The in-pore supporting step includes: a step of adding and mixing an aqueous solution of dinitrodiamine platinum nitric acid to a mesoporous carbon support to obtain a platinum-supported carbon slurry; a step of drying the obtained slurry at a predetermined temperature under reduced pressure to obtain a dry solid; a step of reducing dinitrodiammine platinum by heat treatment in the presence of L-ascorbic acid; and a step of growing platinum particles by firing in an inert gas atmosphere (firing temperature T1), The outside-pore supporting step includes: The mesoporous carbon support having platinum supported in the pores after the intrapore supporting step is suspended in an aqueous nitric acid solution; a step of heating and stirring the suspension, an aqueous solution of dinitrodiamine platinum nitrate, and a liquid containing L-ascorbic acid at 80°C to 100°C for 30 minutes to 5 hours to support platinum particles outside the pores of the carbon support; a step of filtering out the platinum-supported carbon in which platinum particles are supported outside the pores of the carbon support in the above step, washing the carbon support, drying the carbon support, and then firing the carbon support in an inert gas atmosphere (at a firing temperature T2) to grow platinum particles; The method for producing the platinum-supported carbon catalyst according to claim 3, comprising:

5. a step of adding an aqueous solution containing a compound of a metal to be alloyed with the platinum to the platinum-supported carbon catalyst and mixing them to obtain a slurry; and a step of heating and drying the obtained slurry under reduced pressure to obtain a dry solid. and an alloying step of pre-treating the dried product by calcining in the presence of L-ascorbic acid and then calcining the dried product in an inert gas atmosphere to form an alloy.

6. By setting the baking temperature T1 and the baking temperature T2 to predetermined temperatures, 5. The method for producing a platinum or platinum alloy supported carbon catalyst according to claim 3, wherein the average particle diameter D1 of the platinum particles and the average particle diameter D2 of the platinum particles are controlled.

7. 10. A membrane electrode assembly for a polymer electrolyte fuel cell, comprising an electrode containing the platinum or platinum alloy supported carbon catalyst according to claim 1.

8. 10. A polymer electrolyte fuel cell comprising the platinum or platinum alloy supported carbon catalyst of claim 1 contained in an electrode of a membrane electrode assembly.

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