JP4709477B2 - Method for producing electrode catalyst for fuel cell - Google Patents

Description

【０１２３】
【表２】

【０１２４】
図３より、試料１〜７の電極触媒を用いた電池は、試料８〜１３の電極触媒を用いた電池よりも高い電池電圧が測定された。さらに、白金の担持量が６０〜８０ｗｔ％の触媒を用いた電池において、特に高い電池性能が得られた。
【０１２５】
また、作製された単セル電池の０．１Ａ／ｃｍ²におけるＢＥＴ比表面積と電池電圧を測定した。測定結果を表１、２および図３に示した。
【０１２６】
図４より、試料１〜７の電極触媒を用いた電池は、試料８〜１３の電極触媒を用いた電池よりも高い電池電圧が測定された。さらに、電極触媒のＢＥＴ比表面積が２００〜４００の電極触媒において特に高い電池性能が得られた。
【０１２８】
【発明の効果】
本発明の燃料電池用電極触媒の製造方法は、小さな粒径の白金粒子が多量にカーボンに担持された燃料電池用電極触媒を製造できるため、燃料電池を形成するときに十分な触媒量（白金粒子量）を確保しながらガスの拡散を阻害しない触媒層を形成できる効果を有する。
【図面の簡単な説明】
【図１】 白金担持量と白金粒径の関係を示した図である。
【図２】 試料１の触媒を用いた単セル電池の出力特性を示した図である。
【図３】 白金担持量と電池電圧の関係を示した図である。
【図４】 電極触媒のＢＥＴ比表面積と電池電圧の関係を示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode catalyst for a fuel cell used for an electrode of a fuel cell and a method for producing the same.
[0002]
[Prior art]
In recent years, fuel cells have been developed as clean energy sources.
[0003]
Fuel cells are classified into four types according to the type of electrolyte: phosphoric acid type, solid polymer type, molten carbonate type, and solid oxide type.
[0004]
A polymer electrolyte fuel cell uses an ion exchange membrane that is a kind of polymer membrane as an electrolyte, and has characteristics such as high output density, long life, low temperature operation (room temperature to 100 ° C.), and the like. . Due to these features, polymer fuel cells can be used in power sources for electric vehicles that require a short start-up as well as small size and high output, and for stationary power sources that require long-term trust. Expected.
[0005]
A polymer electrolyte fuel cell has a proton (H⁺) An ion exchange membrane having a conductivity of about 100 μm is used, and a catalyst layer having a thin porous electrode catalyst of about 10 to 30 μm is attached to both sides of the membrane. One electrode (fuel electrode, anode) has hydrogen (H₂) Or modified H₂Rich gas is supplied to the other electrode (oxidant electrode, cathode) with oxygen (O₂) Or air, and operate at room temperature to around 100 ° C. The fuel cell oxidizes fuel into protons at the fuel electrode (Formula 1), reduces oxygen to water at the oxidizer electrode (Formula 2), and generates electricity (Formula 3).
[0006]
[Chemical 1]
H₂→ 2H⁺+ 2e^-
[0007]
[Chemical formula 2]
1 / 2O₂+ 2H⁺+ 2e^-→ H₂O
[0008]
[Chemical 3]
H₂+ 1 / 2O₂→ H₂O
[0009]
The electrode catalyst used for the catalyst layer has a structure in which platinum particles are supported on the surface of carbon powder. Such an electrode catalyst uses, for example, a method in which platinum powder is supported by dispersing carbon powder in an aqueous solution of a platinum compound, stabilizing the platinum complex ion on a carbon support using a reducing agent, and then supporting the platinum. It is manufactured. (For example, see Patent Documents 1 to 10.)
In these patent documents, in the invention in which the particle diameter of the platinum particles is reduced, a sufficient amount of platinum supported cannot be secured. Further, when the amount of platinum particles supported was increased, the particle size of the supported platinum particles was increased.
[0010]
In fuel cells, it has been proposed to increase the catalyst basis weight of an electrode catalyst for the purpose of improving cell performance.
[0011]
However, when the catalyst weight per unit area is increased, there is a problem that the catalyst layer becomes thick and the diffusibility of the fuel gas is lowered, so that the battery output cannot be sufficiently obtained. Further, when the catalyst weight per unit area is increased, there is a problem that platinum particles are aggregated and sufficient catalytic activity cannot be obtained, and the battery voltage is lowered.
[0012]
[Patent Document 1]
JP-A-8-162133
[Patent Document 2]
JP-A-10-334925
[Patent Document 3]
JP-A-11-250918
[Patent Document 4]
JP 2000-12043 A
[Patent Document 5]
JP 2001-216991 A
[Patent Document 6]
JP 2002-222655 A
[Patent Document 7]
JP-T-2001-525247
[Patent Document 8]
Japanese translation of PCT publication No. 2002-511639
[Patent Document 9]
Japanese Patent Laid-Open No. 9-167620
[Patent Document 10]
JP 2000-123843 A
[0013]
[Problems to be solved by the invention]
  The present invention has been made in view of the above circumstances, and is an electrode catalyst for a fuel cell that can form a catalyst layer that does not inhibit gas diffusion while having a sufficient amount of catalyst.Manufacturing methodIt is an issue to provide.
[0014]
[Means for Solving the Problems]
  In order to solve the above problems, the present inventors haveAs a result of repeated studies, the present invention has been made.
[0016]
  Of the present inventionFirstThe method for producing a fuel cell electrode catalyst is as follows:A dispersion adjusting step of preparing a dispersion in which the carbon powder and the platinum complex are dissolved, and a washing step of filtering and washing the solid content from the dispersion, and dispersing the solid content in water.a dispersion solution adjusting step of preparing a dispersion solution in which carbon powder and a platinum complex whose pH is maintained at 4 to 7 are dispersed in water, a buffer agent adding step of adding a buffer agent to the dispersion solution, and a reducing agent in the dispersion solution And a reduction precipitation step of reducing and precipitating platinum on the surface of the carbon powder, and a BET specific surface area of 200 to 400 m²/ G of a fuel cell electrode catalyst is produced.
  The second method for producing an electrode catalyst for a fuel cell according to the present invention includes a dispersion step of preparing a dispersion in which carbon powder and a platinum complex are dissolved, and colloidal particles are generated by adding hydrogen peroxide to the dispersion. A colloid producing step, and a washing step in which the solid content is separated from the dispersion and washed, and the solid content is dispersed in water, and the carbon powder and the platinum complex maintained at pH 4 to 7 are dispersed in water. A dispersion solution adjustment step for preparing the dispersion solution, a buffer addition step for adding a buffer agent to the dispersion solution, and a reduction deposition step for reducing and precipitating platinum on the surface of the carbon powder by adding a reducing agent to the dispersion solution. Having a BET specific surface area of 200 to 400 m ² / G of a fuel cell electrode catalyst is produced.
[0017]
The fuel cell electrode catalyst of the present invention has a catalyst layer that does not inhibit gas diffusion while ensuring a sufficient amount of catalyst (amount of platinum particles) since a large amount of platinum particles having a small particle size are supported on carbon. An electrode catalyst for a fuel cell that can be formed can be provided.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
  (Electrocatalyst for fuel cell)
  The present inventionManufactured by the manufacturing methodFuel cell electrode catalyst(Hereinafter referred to as the fuel cell electrode catalyst of the present invention)Has a configuration in which platinum particles are supported on carbon. The fuel cell catalyst of the present invention has a structure in which platinum particles are supported on carbon, thereby increasing the reaction surface area and increasing the activity per unit catalyst weight.
[0019]
The average particle diameter of the platinum particles is 1.9 to 2.3 nm. By adjusting the average particle size of the platinum particles, when the electrode catalyst of the present invention is used for an electrode of a fuel cell, the fuel cell can obtain sufficient cell performance. The platinum particles supported on carbon are made of pure platinum.
[0020]
The smaller the particle diameter of the platinum particles, the larger the surface area of the platinum particles when carrying the same weight of platinum particles. That is, it is preferable that the average particle diameter of the platinum particles is small. If the average particle diameter of the platinum particles exceeds 2.3 nm, the catalyst surface area of the fuel cell electrode is not ensured, and the battery output decreases. On the other hand, when the average particle size is less than 1.9 nm, the particle size of the platinum particles is too small and it becomes difficult to support the carbon.
[0021]
The particle diameter of the platinum particles can be determined by measuring the XRD of the electrode catalyst and calculating from the half-value width of a peak around 39 ° (derived from the (111) plane of Pt).
[0022]
When the fuel cell electrode catalyst is 100 wt%, the platinum particles are 60 to 80 wt%. By adjusting the amount of platinum particles supported on carbon, when the electrode catalyst of the present invention is used for an electrode of a fuel cell, the fuel cell can obtain sufficient cell performance.
[0023]
When the supported amount of platinum particles is less than 60 wt%, the catalyst layer becomes thick, the fuel gas diffusibility decreases, and the battery output decreases. On the other hand, when the loading amount exceeds 80 wt%, the activity becomes remarkably high, causing a problem of ignition.
[0024]
The fuel cell electrode catalyst of the present invention has a BET specific surface area of 200 to 400 m.²/ G is preferable. By adjusting the BET specific surface area, when the electrode catalyst of the present invention is used for an electrode of a fuel cell, the fuel cell can obtain sufficient cell performance.
[0025]
Specific surface area 200m²If it is less than / g, sufficient catalytic activity cannot be obtained, so the battery performance decreases, and 400 m²When the amount exceeds / g, a large amount of water generated during power generation is adsorbed, and the battery performance is lowered due to a decrease in water discharge performance.
[0026]
In the fuel cell electrode catalyst of the present invention, as the carbon on which the platinum particles are supported, the carbon used in the conventional fuel cell electrode catalyst can be used. For example, carbon black and activated carbon can be mentioned.
[0027]
  The fuel cell catalyst of the present invention comprises:Claims 1-6According to the manufacturing method described inManufactured.
[0028]
In the fuel cell electrode catalyst of the present invention, since platinum particles having an average particle size of 1.9 to 2.3 nm were supported on carbon, the catalyst surface area was sufficiently secured. Can be reduced. As a result, the fuel cell electrode catalyst of the present invention can provide a fuel cell electrode catalyst capable of forming a catalyst layer that does not inhibit gas diffusion while ensuring a sufficient catalyst amount (platinum particle amount).
[0029]
  (Production method)
  Of the present inventionFirstThe method for producing a fuel cell electrode catalyst includes a dispersion solution adjustment step, a buffer addition step, and a reduction precipitation step. In the production method of the present invention, a solution in which carbon powder having a pH of 4 to 7 and platinum are dispersed is used.In the process of having a dispersion adjustment process and a cleaning processThis is a production method for producing an electrode catalyst for a fuel cell by preparing and reducing and precipitating platinum on the surface of a carbon powder.
[0030]
  Of the first manufacturing methodThe dispersion solution adjustment processHaving a washing step,This is a step of preparing a dispersion solution in which a carbon powder whose pH is maintained at 4 to 7 and a platinum complex are dispersed in water. That is, the dispersion solution adjustment stepA dispersion adjustment step, and a washing step,This is a step of preparing a dispersion solution having a pH maintained at 4 to 7 and containing a carbon powder and platinum.
  The manufacturing method of the 2nd electrode catalyst for fuel cells of this invention has a dispersion solution adjustment process, a buffer agent addition process, and a reduction | restoration precipitation process. In the production method of the present invention, a solution in which platinum and carbon powder having a pH of 4 to 7 are dispersed is prepared in a step having a dispersion step, a colloid generation step, and a washing step, and platinum is reduced on the surface of the carbon powder It is a manufacturing method which manufactures the electrode catalyst for fuel cells by making it precipitate.
  The dispersion solution adjustment step of the second production method is a step of preparing a dispersion solution having a washing step, in which carbon powder having a pH maintained at 4 to 7 and a platinum complex are dispersed in water. That is, the dispersion solution adjustment step includes a dispersion step, a colloid generation step, and a washing step, and is a dispersion solution that maintains a pH of 4 to 7, and prepares a solution containing carbon powder and platinum. It is a process to do.
[0031]
  The first and second production methods of the present invention (hereinafter referred to as the production method of the present invention unless otherwise specified)The buffering agent adding step is a step of adding a buffering agent to the dispersion solution. By adding a buffering agent in the buffering agent addition step, it is possible to control the reduction precipitation reaction in the subsequent reduction precipitation step. By controlling the reaction rate of the reduction precipitation reaction, it is possible to reduce the particle size of platinum to be reduced precipitation.
[0032]
  Of the production method of the present inventionThe reduction deposition step is a step in which a reducing agent is added to the dispersion solution and platinum is reduced and deposited on the surface of the carbon powder. By depositing platinum on the surface of the carbon powder, a fuel cell electrode catalyst in which platinum is supported on carbon can be produced.
[0033]
In the production method of the present invention, the reaction rate of the reduction deposition of platinum in the reduction deposition step is reduced by adding a buffer. When the reaction rate of the reductive precipitation reaction is reduced, the growth rate of the particle size of the particles formed by the reductively deposited platinum is also slowed, so that platinum particles having a small particle size can be obtained. That is, an electrode catalyst in which platinum particles having a small particle diameter are supported on carbon powder is obtained.
[0034]
In the production method of the present invention, the buffer is not limited as long as it is a substance that can control the reaction rate of the reduction precipitation reaction. For example, substances such as acetic acid, citric acid, propionic acid, ammonia, ethanolamine and the like can be mentioned.
[0035]
The reducing agent added to the dispersion solution in the reduction precipitation step is not particularly limited as long as it is a substance that can reduce and precipitate platinum dissolved in the dispersion solution. That is, a conventionally known substance can be used as the reducing agent. Examples of the reducing agent include sodium borohydride aqueous solution, hydrogen gas, alcohol, formic acid, and hydrazine.
[0036]
  In the first manufacturing method,The dispersion solution adjusting step includes a dispersion adjusting step of preparing a dispersion in which the carbon powder and the platinum complex are dissolved, and a washing step of filtering and washing the solid content from the dispersion and dispersing the solid content in water.Process.
[0037]
The dispersion solution adjustment process prepares a dispersion liquid in which carbon and platinum are mixed in the dispersion adjustment process, and the carbon with the platinum complex attached to the surface is prepared by filtering and washing the solid content from the dispersion liquid. Can do. Then, by dispersing this carbon again in water, a dispersion solution in which the platinum complex and the carbon are dispersed is obtained.
[0038]
The carbon powder used for the electrode catalyst for fuel cells has a certain high specific surface area and is difficult to disperse in a solution such as water. For this reason, it is preferable to disperse in water in advance and mix with the solution in which the platinum complex is dissolved, rather than injecting the carbon powder into the solution in which the platinum complex is dissolved. That is, the dispersion liquid adjusting step is a dispersion step of preparing a dispersion by dispersing carbon powder in water, a platinum aqueous solution adjusting step of preparing a platinum aqueous solution in which a platinum complex is dissolved, and an addition of adding a platinum aqueous solution to the dispersion It is preferable to have a process.
[0039]
Moreover, since this dispersion | distribution solution adjustment process has a washing | cleaning process, the pH of the dispersion liquid prepared is maintained at 4-7 (neutral). By maintaining the dispersion in neutrality, the amount of buffering agent added can be reduced in subsequent steps. In the washing step, it is preferable to wash with running water until the conductivity of the waste water becomes 100 μS / cm or less.
[0040]
  In the second manufacturing method,The dispersion solution adjustment step includes a dispersion step of preparing a dispersion in which carbon powder and platinum complex are dissolved, a colloid generation step of adding hydrogen peroxide to the dispersion to generate colloid particles, and a solid content from the dispersion. Washing by filtering and washing, and dispersing the solid content in water;Process.
[0041]
That is, the platinum complex is dispersed in the dispersion solution as colloidal particles. By dispersing the platinum complex as colloidal particles, the platinum complex can be concentrated and the generation of expensive platinum loss can be suppressed. And carbon which a platinum complex adhered to the surface can be prepared by separating and washing solid content from this solution. Then, by dispersing this carbon again in water, a dispersion solution in which the platinum complex and the carbon are dispersed is obtained.
[0042]
Moreover, since the dispersion solution adjustment process which has a colloid production | generation process has a washing | cleaning process, the pH of the prepared dispersion solution is maintained at 4-7 (neutral). By maintaining the dispersion in neutrality, the amount of buffer added can be reduced in subsequent steps. In the washing step, it is preferable to wash with running water until the conductivity of the waste water becomes 100 μS / cm or less.
[0043]
In the production method of the present invention, the carbon powder is not particularly limited as long as it can support the reduced and precipitated platinum particles and has conductivity. Carbon used in conventional fuel cell electrode catalysts can be used. For example, carbon black and activated carbon can be mentioned.
[0044]
Carbon powder is 800-1500m²It is preferable to have a BET specific surface area of / g. Carbon powder is 800-1500m²By having a BET specific surface area of / g, the produced electrode catalyst has a sufficient specific surface area.
[0045]
In the production method of the present invention, the platinum complex may be any substance that can reduce and precipitate platinum in the reduction and precipitation step. The platinum complex currently used for the conventional electrode catalyst for fuel cells can be used. For example, a hexahydroxo platinum complex and a dinitrodiamino platinum complex can be mentioned.
[0046]
The production method of the present invention can produce a fuel cell electrode catalyst made of carbon powder in which a large amount of fine platinum particles are supported by controlling the reaction rate of the precipitation reaction with a buffer. This electrode catalyst can provide a fuel cell electrode catalyst capable of forming a catalyst layer that does not inhibit gas diffusion while ensuring a sufficient amount of catalyst (amount of platinum particles).
[0047]
The fuel cell electrode catalyst and the fuel cell electrode catalyst produced by using the production method are used for a polymer electrolyte fuel cell electrode.
[0048]
For example, an electrode for a solid polymer fuel cell is formed by forming a catalyst layer containing an electrode catalyst and polymer electrolyte particles on one surface of a support substrate made of water-repellent conductive porous carbon.
[0049]
Carbon paper or carbon cloth can be used as the support substrate made of conductive porous carbon.
[0050]
As the polymer electrolyte, a proton conductive polymer having a cation exchange group such as a sulfonic acid group or a carboxyl group in the side chain is usually used. Specific examples of such a conductive polymer include a perfluoropolymer having a sulfonic acid group (hereinafter referred to as a perfluorosulfonic acid polymer).
[0051]
As the conductive carbon powder, the same carbon powder as that used for the electrode catalyst carrier can be used.
[0052]
Such an electrode for a polymer electrolyte fuel cell can be produced by the following procedure.
[0053]
As another method for forming a catalyst layer containing an electrode catalyst and polymer electrolyte particles on the carbon powder layer, the electrode catalyst was made into a slurry or paste together with a water-repellent resin, and this was applied onto the carbon powder layer and then prepared in advance. A solution of polyelectrolyte particles is impregnated or applied. Next, this coated material is air-dried at room temperature and then dried at 60 to 100 ° C.
[0054]
In the above production method, the carbon powder layer may be omitted, and the catalyst layer may be directly formed on the support substrate that has been subjected to the water-repellent treatment. In this case, it is preferable to add a water repellent resin to the catalyst layer. As the coating method, a spray method, a filtration method, a roll coater method, a printing method, or the like can be applied. The thickness of the support base is usually 50 to 400 μm, preferably 150 to 350 μm. The thickness of the carbon powder layer is usually 100 μm or less, preferably 70 μm or less. The thickness of the catalyst layer is usually 5 to 120 μm, preferably 10 to 70 μm.
[0055]
The electrode thus produced can be used as an anode electrode and a cathode electrode, preferably an anode electrode of a polymer electrolyte fuel cell.
[0056]
In the polymer electrolyte fuel cell, the solid polymer electrolyte and the electrode may be separate or may form an electrolyte membrane-electrode assembly in which both are joined. It is preferable to form an electrolyte membrane-electrode assembly.
[0057]
The electrolyte membrane-electrode assembly is configured by providing a catalyst layer containing an electrode catalyst and polymer electrolyte particles and a conductive porous support substrate in this order on both sides of a solid polymer electrolyte membrane. Both catalyst layers or one of the catalyst layers is a catalyst layer used for a fuel cell electrode. Therefore, the electrolyte membrane-electrode assembly may be in a form in which the electrode is formed on both sides of the solid polymer electrolyte membrane, or the electrode is formed on one side of the solid polymer electrolyte membrane and separated on the other side. The form in which the electrode is formed may be used.
[0058]
The solid polymer electrolyte membrane is usually a membrane made of a polymer having a cation exchange group such as a sulfonic acid group or a carboxyl group in the side chain. Specific examples of the polymer for the electrolyte membrane include those similar to the conductive polymer described above. Among these, commercially available Nafion (manufactured by Deyupon) is preferably used as a membrane of perfluorosulfonic acid polymer.
[0059]
There is no restriction | limiting in particular in the manufacturing method of an electrolyte membrane-electrode assembly, A conventionally well-known method can be used.
[0060]
For example, when the electrode is formed only on one surface of the solid polymer electrolyte membrane, the electrode is produced by superimposing the catalyst layer side of the electrode on the surface of the solid polymer electrolyte membrane and press-bonding it with a press. In addition, when the electrodes are formed on both sides of the solid polymer electrolyte membrane, the electrodes are superimposed on the surface of the solid polymer electrolyte membrane on the both sides of the solid polymer electrolyte membrane and pressed with a press. Good. When the electrode is formed on one surface of the solid polymer electrolyte membrane and another electrode is formed on the other surface, the electrode is superimposed on one surface of the solid polymer electrolyte membrane and separated on the other surface. These electrodes may be stacked and pressure-bonded with a press.
[0061]
As another method for producing an electrolyte membrane-electrode assembly, for example, a catalyst layer containing an electrode catalyst and polymer electrolyte particles is formed on one surface or both surfaces of a solid polymer electrolyte membrane, and then repellent on the catalyst layer. An example is a method in which a water-treated support base material is superposed and then pressure-bonded by a press. At this time, if necessary, a carbon powder layer containing a conductive carbon powder and a water-repellent resin may be formed in advance on the surface on which the supporting base material is overlapped.
[0062]
As a method for forming a catalyst layer containing an electrode catalyst and polymer electrolyte particles on one or both surfaces of a solid polymer electrolyte membrane, for example, an electrode catalyst and polymer electrolyte particles are mixed, and further prepared as necessary. An example is a method in which a pore material is added to form a slurry or paste, which is applied to one or both sides of a solid polymer electrolyte membrane, air-dried at room temperature, and then dried at 60 to 100 ° C. When the pore former is used, after forming the catalyst layer, the pore former in the layer is dissolved in a solvent such as water, or is baked and decomposed at 150 to 250 ° C. Remove it. There is no restriction | limiting in particular in the method to apply | coat, A screen printing method, a doctor blade method, a roll coater method etc. can be used. As the pore former, for example, ammonium carbonate or polyvinyl alcohol can be used.
[0063]
In the electrolyte membrane-electrode assembly thus manufactured, one electrode is an anode electrode and the other electrode is a cathode electrode. Also in an electrolyte membrane-electrode assembly in which electrodes are formed on both surfaces of a solid polymer electrolyte membrane, one electrode is an anode electrode and the other electrode is a cathode electrode. In the electrolyte membrane-electrode assembly in which the electrode is formed on one surface of the solid polymer electrolyte membrane and another electrode is formed on the other surface, the electrode joined by the function of the joined another electrode Can be used as an anode electrode or a cathode electrode.
[0064]
The polymer electrolyte fuel cell includes an anode gas distribution plate and a cathode gas distribution plate, each serving as a current collector plate, in each of the gas diffusion layers (support base materials) of the anode electrode and the cathode electrode of the electrolyte membrane-electrode assembly. Arranged.
[0065]
The gas distribution plate may be one conventionally used in this type of fuel cell. For example, a gas distribution groove having a desired depth is formed on a desired portion of one side of a gas-impermeable dense carbon plate. And what used also as the current collecting plate which provided the gasket part for a gas seal in the circumference | surroundings can be used.
[0066]
As a gasket for gas sealing, a packing made of fluororesin, for example, a sheet made of polytetrafluoroethylene, an O-ring made of vinylidene fluoride / 6-propylene propylene copolymer, or the like can be used.
[0067]
In order to produce a fuel cell (single cell battery), two gas distribution plates are prepared, and the surface of each gas distribution plate having a groove is formed on each of the gas diffusion layers of the anode and the cathode of the electrolyte membrane-electrode assembly. Further, the gas distribution plates on both sides may be sandwiched between metal plates provided with gas supply ports and gas discharge ports, such as stainless steel plates, and fixed. In addition, a reactive gas flow path (anode gas is passed through one side and a cathode gas passed through the other side) is provided on both sides of a separator bipolar plate made of a gas-impermeable dense carbon material, and adjacent single units are provided. Cell batteries can be connected in series to form a laminated battery. Furthermore, it is possible to embed a cooling pipe every several batteries in the separator to remove the heat of reaction accompanying the battery reaction and to recover the heat. In order to operate this fuel cell, air or oxygen is supplied to the cathode while reforming gas (alcohol, hydrocarbon, etc.) is supplied to the cathode while humidifying the electrolyte membrane through heated steam through the gas supply ports of the anode and cathode electrodes. The hydrogen-enriched gas obtained by reforming the above fuel may be supplied.
[0068]
【Example】
Hereinafter, the present invention will be described using examples.
[0069]
As an example of the present invention, a catalyst for a fuel cell electrode was produced.
[0070]
(Sample 1)
A slurry was prepared by adding 2.5 g of high specific surface area carbon powder (trade name: Printex, manufactured by Degussa) to 0.2 L of pure water. In a state where the slurry was stirred, 150 g (7.5 g in terms of platinum) of 5 wt% hexahydroxoplatinum nitric acid aqueous solution was dropped to allow the platinum and carbon to blend together. 1 L of pure water was further added dropwise to the obtained solution, and then filtered. The powder separated by filtration was washed with pure water until the drainage conductivity was 100 μS / cm or less.
[0071]
The obtained powder was dispersed in 1 L of pure water. 0.01N ammonia solution was added dropwise to adjust the pH to 9 (approximately 5 mL added dropwise). Subsequently, 170 mL of a 3 wt% aqueous sodium borohydride solution was dropped and stirred sufficiently. Thereafter, the powder was filtered off. The powder separated by filtration was washed with pure water until the drainage conductivity was 100 μS / cm or less.
[0072]
The resulting powder was dried by heating at 80 ° C. for 48 hours.
[0073]
The fuel cell electrode catalyst of this sample was manufactured by the above means.
[0074]
The supported amount of Pt in the catalyst of this sample was 75.0 wt%, and the particle size of the supported Pt was 2.0 to 2.2 nm. Moreover, when the BET specific surface area was measured, it was 250 m.²/ G.
[0075]
Here, the particle size of Pt was measured by measuring the XRD of the catalyst and calculating from the half-value width of a peak near 39 ° (derived from the (111) plane of Pt).
[0076]
(Sample 2)
A slurry was prepared by adding 2.0 g of the same high specific surface area carbon powder as used in Sample 1 to 0.2 L of pure water. A platinum aqueous solution prepared by dissolving 8.0 g of dinitrodiaminoplatinum nitrate in 1 L of pure water in terms of platinum was prepared, and 2.0 g of carbon powder (a product similar to Sample 1) was added and dispersed in this platinum aqueous solution. And in the state which stirred the slurry, platinum aqueous solution was dripped and platinum and carbon were blended.
[0077]
To the obtained slurry, 0.3 L of ethanol (purity 99.5%) was further added and stirred sufficiently. Subsequently, 5 mL of 0.01N acetic acid was added dropwise. Thereafter, the powder was filtered off. The powder separated by filtration was washed with pure water until the drainage conductivity was 100 μS / cm or less.
[0078]
The resulting powder was dried by heating at 80 ° C. for 48 hours.
[0079]
The fuel cell electrode catalyst of this sample was manufactured by the above means.
[0080]
The supported amount of Pt in the catalyst of this sample was 80.0 wt%, and the particle size of the supported Pt was 2.1 to 2.2 nm. Moreover, when the BET specific surface area was measured, it was 200 m.²/ G.
[0081]
(Sample 3)
A slurry was prepared by adding 4.0 g of the same high specific surface area carbon powder as used in Sample 1 to 1 L of pure water. While stirring this slurry, 150 g (6.0 g in terms of platinum) of 4 wt% hexahydroxo platinum sulfite aqueous solution was dropped to allow platinum and carbon to blend together. Furthermore, 120 mL of 35 vol% hydrogen peroxide water was added to this slurry to produce colloidal particles in which platinum oxide was supported on carbon powder. The obtained colloidal solution was heated to reflux and then subjected to filtration and washing treatment to obtain a powder.
[0082]
The obtained powder was dispersed in 1 L of pure water, and 0.01N ammonia solution was added dropwise to adjust the pH to 9 (approximately 5 mL added dropwise). Subsequently, 140 mL of a 3 wt% aqueous sodium borohydride solution was added dropwise and stirred sufficiently. Thereafter, the powder was filtered off. The powder separated by filtration was washed with pure water until the drainage conductivity was 100 μS / cm or less.
[0083]
The resulting powder was dried by heating at 80 ° C. for 48 hours.
[0084]
The fuel cell electrode catalyst of this sample was manufactured by the above means.
[0085]
The supported amount of Pt in the catalyst of this sample was 60.0 wt%, and the particle size of the supported Pt was 1.9 to 2.1 nm. Moreover, when the BET specific surface area was measured, it was 400 m.²/ G.
[0086]
(Sample 4)
The fuel cell electrode catalyst was produced in the same manner as Sample 1, except that 7.0 g of the high specific surface area carbon powder and 60 g (3.0 g in terms of platinum) of the hexahydrosoplatinum nitric acid aqueous solution were added dropwise.
[0087]
The supported amount of Pt in the catalyst of this sample was 30.0 wt%, and the particle size of the supported Pt was 1.6 to 1.8 nm. The BET specific surface area is 700m.²/ G.
[0088]
(Sample 5)
It is a fuel cell electrode catalyst produced in the same manner as Sample 1 except that 6.0 g of the high specific surface area carbon powder and 80 g (4.0 g in terms of platinum) of the hexahydroso platinum nitric acid aqueous solution were added.
[0089]
The supported amount of Pt in the catalyst of this sample was 40.0 wt%, and the particle size of the supported Pt was 1.7 to 1.9 nm. The BET specific surface area is 600m.²/ G.
[0090]
(Sample 6)
The fuel cell electrode catalyst was produced in the same manner as Sample 1 except that 5.0 g of the high specific surface area carbon powder and 100 g (5.0 g in terms of platinum) of the hexahydroso platinum nitric acid aqueous solution were added dropwise.
[0091]
The supported amount of Pt in the catalyst of this sample was 50.0 wt%, and the particle size of the supported Pt was 1.8 to 2.0 nm. The BET specific surface area is 500m.²/ G.
[0092]
(Sample 7)
The fuel cell electrode catalyst was produced in the same manner as Sample 1, except that 4.0 g of the high specific surface area carbon powder and 120 g (6.0 g in terms of platinum) of the hexahydrosoplatinic acid aqueous solution were added dropwise.
[0093]
The supported amount of Pt in the catalyst of this sample was 90.0 wt%, and the particle size of the supported Pt was 2.2 to 2.3 nm. The BET specific surface area is 100m.²/ G.
[0094]
(Sample 8)
A slurry was prepared by adding 7.0 g of the same high specific surface area carbon powder as used in Sample 1 to 0.2 L of pure water. While stirring the slurry, 60 g (3.0 g in terms of platinum) of a 5 wt% hexahydroxoplatinum nitric acid aqueous solution was dropped to allow the platinum and carbon to blend together. 1 L of pure water was further added dropwise to the obtained solution, and then filtered. The powder separated by filtration was washed with pure water until the drainage conductivity was 100 μS / cm or less.
[0095]
The obtained powder was dispersed in 1 L of pure water. 70 g of 3 wt% aqueous sodium borohydride solution was added dropwise and stirred sufficiently. Thereafter, the powder was filtered off. The powder separated by filtration was washed with pure water until the drainage conductivity was 100 μS / cm or less.
[0096]
The resulting powder was dried by heating at 80 ° C. for 48 hours.
[0097]
The fuel cell electrode catalyst of this sample was manufactured by the above means.
[0098]
The supported amount of Pt in the catalyst of this sample was 30.0 wt%, and the particle size of the supported Pt was 1.7 to 1.9 nm. Moreover, when the BET specific surface area was measured, it was 690 m.²/ G.
[0099]
  (Sample 9)
  Except for 6.0 g of high specific surface area carbon powder and 80 g of hexahydrosoplatinic acid nitric acid aqueous solution (4.0 g in terms of platinum),Sample 8It is the catalyst for fuel cell electrodes manufactured similarly.
[0100]
The supported amount of Pt in the catalyst of this sample was 40.0 wt%, and the particle size of the supported Pt was 1.9 to 2.2 nm. The BET specific surface area is 580 m.²/ G.
[0101]
  (Sample 10)
  Except for 5.0 g of the high specific surface area carbon powder and 100 g (5.0 g in terms of platinum) of the dropping amount of the hexahydroso platinum nitric acid aqueous solution,Sample 8It is the catalyst for fuel cell electrodes manufactured similarly.
[0102]
The supported amount of Pt in the catalyst of this sample was 50.0 wt%, and the particle size of the supported Pt was 2.1 to 2.3 nm. The BET specific surface area is 470m.²/ G.
[0103]
  (Sample 11)
  Except for 4.0 g of high specific surface area carbon powder and 120 g (6.0 g in terms of platinum) of dropping amount of hexahydrosoplatinic acid aqueous solution,Sample 8It is the catalyst for fuel cell electrodes manufactured similarly.
[0104]
The supported amount of Pt in the catalyst of this sample was 60.0 wt%, and the particle size of the supported Pt was 2.3 to 2.7 nm. The BET specific surface area is 350m.²/ G.
[0105]
  (Sample 12)
  Except for the high specific surface area carbon powder 2.5g and the dropping amount of the hexahydroso platinum nitric acid aqueous solution 150g (7.5g in terms of platinum),Sample 8It is the catalyst for fuel cell electrodes manufactured similarly.
[0106]
The supported amount of Pt in the catalyst of this sample was 75.0 wt%, and the particle size of the supported Pt was 3.0 to 3.3 nm. The BET specific surface area is 200m.²/ G.
[0107]
  (Sample 13)
  Except for 2.0 g of the high specific surface area carbon powder and 160 g (8.0 g in terms of platinum) of the dropping amount of the hexahydroso platinum nitric acid aqueous solution,Sample 8It is the catalyst for fuel cell electrodes manufactured similarly.
[0108]
The supported amount of Pt in the catalyst of this sample was 80.0 wt%, and the particle size of the supported Pt was 3.5 to 4.0 nm. The BET specific surface area is 150m.²/ G.
[0109]
(Evaluation)
First, FIG. 1 shows the relationship between the amount of platinum supported on the catalyst of each sample and the particle size of the supported platinum. In FIG. 1, a distinction is made between an example in which platinum is deposited under conditions where a buffering agent is present, and other examples.
[0110]
From FIG. 1, the catalyst of Samples 1 to 7 using the production method of the present invention has a smaller particle size of platinum particles than the catalysts of Samples 8 to 13. That is, since the electrode catalysts of Samples 1 to 7 can carry platinum particles having a small particle diameter even when the amount of platinum carried is increased, a large amount of platinum can be carried.
[0111]
Subsequently, an electrode for a single cell of a polymer electrolyte fuel cell and a single cell battery using this electrode were manufactured using the catalyst of each sample, and the battery characteristics were measured.
[0112]
(Manufacture of electrodes)
1.5 g of catalyst powder of each sample was mixed with 10% Nafion solution (Aldrich). Alcohol was added to this mixed solution to make the total weight 20 g. This mixed solution was subjected to a dispersion treatment for 5 minutes with an ultrasonic disperser to obtain a uniform dispersion.
[0113]
Thereafter, this dispersion was applied onto a fluororesin sheet to form a coating film. The obtained coating film was put into a vacuum dryer and dried at 100 ° C. for 1 hour to form a catalyst layer.
[0114]
And the manufactured catalyst layer was laminated | stacked via the electrolyte membrane (brand name: Nafion), and it hot-pressed on 120 degreeC, 10 kPa, and the conditions for 5 minutes, and bonded together.
[0115]
The electrode was manufactured as described above. The manufactured electrode has an electrode area of 1 cm.²The amount of catalyst per unit was 0.4 mg.
[0116]
(Manufacture of single cell batteries)
A gas distribution groove with a pitch of 5 mm is formed in a square portion of 40 × 40 mm on one side of a dense carbon plate, and a vinylidene fluoride / 6-propylene propylene copolymer (Viton made by DuPont) is formed around the groove. Two gas distribution plates serving as current collector plates were prepared by fitting the O-rings. These gas distribution plate grooves are fitted to contact the gas diffusion layers of the anode and cathode of the electrolyte membrane-electrode assembly prepared above, and the gas distribution plates on both sides are fitted to the gas distribution plates. It is sandwiched between a stainless steel plate provided with a supply port and a gas discharge port, and the stainless steel plate is uniformly tightened with bolts at several end portions to obtain an effective electrode area of 16 cm.²A single cell battery of a polymer electrolyte fuel cell having the following structure was prepared.
[0117]
(Measurement of battery characteristics)
Among the produced single cell batteries, the output characteristics (current-voltage) of the single cell batteries using the catalysts of Sample 1 and Sample 12 were measured, and the measurement results are shown in FIG.
[0118]
For measurement of output characteristics, hydrogen was supplied to the anode electrode (fuel electrode) of the single cell battery at a flow rate of 500 mL / min, and air was supplied to the cathode electrode (oxidant electrode) at a flow rate of 1 L / min. This was done by measuring the current-voltage characteristics.
[0119]
As shown in FIG. 2, the battery using the sample 1 which is the electrode catalyst of the present invention has a gas diffusive rate-determining 0.9 A / cm.²It can be seen that the voltage drop is small in the high current region. On the other hand, the battery using the sample 12 has a large voltage drop in the high current region.
[0120]
Moreover, 0.9 A / cm of the produced single cell battery²The battery voltage at was measured. The measurement results are shown in Tables 1 and 2 and FIGS.
[0121]
Battery voltage measurement is 0.9A / cm²For about 2 hours and measuring the stabilized voltage value.
[0122]
[Table 1]

[0123]
[Table 2]

[0124]
From FIG. 3, the battery using the electrode catalyst of Samples 1-7 was measured to have a higher battery voltage than the battery using the electrode catalyst of Samples 8-13. Furthermore, particularly high battery performance was obtained in a battery using a catalyst having a platinum loading of 60 to 80 wt%.
[0125]
Moreover, 0.1 A / cm of the produced single cell battery²The BET specific surface area and battery voltage were measured. The measurement results are shown in Tables 1 and 2 and FIG.
[0126]
From FIG. 4, the battery using the electrode catalyst of Samples 1 to 7 measured a higher battery voltage than the battery using the electrode catalyst of Samples 8 to 13. Furthermore, particularly high battery performance was obtained with an electrode catalyst having a BET specific surface area of 200 to 400.
[0128]
【The invention's effect】
  Of the present inventionThe method for producing an electrode catalyst for a fuel cell is that a large amount of platinum particles having a small particle size are supported on carbon.For fuel cellBecause we can manufacture electrode catalyst,When forming a fuel cellThis has the effect of forming a catalyst layer that does not inhibit gas diffusion while ensuring a sufficient amount of catalyst (platinum particle amount).
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between platinum loading and platinum particle size.
2 is a graph showing output characteristics of a single cell battery using the catalyst of Sample 1. FIG.
FIG. 3 is a diagram showing the relationship between platinum loading and battery voltage.
FIG. 4 is a graph showing the relationship between the BET specific surface area of the electrode catalyst and the battery voltage.

Claims (6)

A dispersion adjusting step for preparing a dispersion in which the carbon powder and the platinum complex are dissolved, and a washing step for filtering and washing the solid content from the dispersion, and dispersing the solid content in water. A dispersion solution adjusting step of preparing a dispersion solution in which the carbon powder maintained at ˜7 and the platinum complex are dispersed in water;
A buffering agent adding step of adding a buffering agent to the dispersion;
A reduction deposition step of adding a reducing agent to the dispersion solution to reduce and deposit platinum on the surface of the carbon powder;
And a fuel cell electrode catalyst having a BET specific surface area of 200 to 400 m ² / g is produced.   The method for producing a fuel cell electrode catalyst according to claim 1, wherein the buffer is selected from acetic acid, citric acid, propionic acid, ammonia, and ethanolamine. The method for producing an electrode catalyst for a fuel cell according to claim 1 , wherein the washing step is carried out with running water until the conductivity of the waste water becomes 100 μS / cm or less. A dispersion step of preparing a dispersion in which the carbon powder and the platinum complex are dissolved, a colloid generation step in which hydrogen peroxide water is added to the dispersion to generate colloid particles, and a solid content is separated from the dispersion and washed. A dispersion step for preparing a dispersion solution in which the carbon powder having the pH maintained at 4 to 7 and the platinum complex are dispersed in water.
A buffering agent adding step of adding a buffering agent to the dispersion;
A reduction deposition step of adding a reducing agent to the dispersion solution to reduce and deposit platinum on the surface of the carbon powder;
And a fuel cell electrode catalyst having a BET specific surface area of 200 to 400 m ² / g is produced. The method for producing an electrode catalyst for a fuel cell according to claim 4 , wherein the buffer is selected from acetic acid, citric acid, propionic acid, ammonia, and ethanolamine. The method for producing an electrode catalyst for a fuel cell according to claim 4 , wherein the washing step is carried out with running water until the conductivity of the waste water becomes 100 μS / cm or less.

Images