JP4204272B2 - Fuel cell electrode catalyst and fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode catalyst for a fuel cell and a fuel cell.
[0002]
[Prior art]
Solid polymer electrolyte fuel cells (PEFC) are attracting attention as an energy source for transportation instead of conventional internal combustion engines because they have high power density, operate at low temperatures, and emit almost no exhaust gas containing harmful substances. .
[0003]
The theoretical voltage of the output terminal of PEFC is 1.23V, but only a value far from this value is actually obtained due to various polarizations. The decrease in the voltage at the output terminal means a decrease in the efficiency of PEFC. In order to increase the practicality of PEFC that requires further improvement in efficiency, it is desired to suppress the polarization and increase the output density.
[0004]
The PEFC is configured by joining an anode to one surface of a solid polymer electrolyte membrane and a cathode to the other surface. For example, PEFC is supplied with hydrogen as a fuel and oxygen as an oxidant to the cathode. Then, the fuel is oxidized to protons at the anode, and oxygen is reduced to water at the cathode to generate power. A fuel cell electrode catalyst made of fine powder in which catalyst particles made of a noble metal such as Pt are supported on a carrier such as carbon is used for both the anode and the cathode.
[0005]
Here, the cathode of PEFC is a main factor that determines the power generation characteristics, and its activity improvement is an important issue. In addition to the metal supported as catalyst particles, improvement of the carrier itself is considered to be an effective means.
[0006]
Further, the catalyst particles supported on the carrier constituting the fuel cell electrode catalyst often have an expensive element such as Pt, and its low utilization factor contributes to an increase in cost.
[0007]
[Problems to be solved by the invention]
By the way, the improvement of the carrier used in the conventional fuel cell is limited to the improvement of the furnace black carbon obtained by burning oil and acetylene (surface improvement, etc.), and the investigation of the new carbon material has hardly been performed. Recently, new materials such as carbon nanofibers and carbon nanohorns have been studied, and improvements in catalytic activity due to improvements in electronic conductivity and Pt dispersibility have been reported.
[0008]
Accordingly, an object of the present invention is to provide a fuel cell electrode catalyst that can be used as a fuel cell having a higher output density than a conventional fuel cell electrode catalyst when used in a fuel cell, and a conventional carrier. The object is to provide a fuel cell having a higher power density than the fuel cell.
[0009]
[Means for Solving the Problems and Effects of the Invention]
In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result of conventional electrode catalysts for fuel cells, (1) when catalyst particles such as Pt are supported on a carbon material such as carbon black. (2) The high specific surface area carbon material has cavities inside, so the utilization rate of the supported catalyst particles is low, and (3) the fuel cell electrode catalyst is used as an electrode. It has been found that the path of reactive substances (protons, electrons, reactive gases) is not sufficient when applied to the catalyst, and the catalyst particles cannot be used effectively. The electrode catalyst for a fuel cell of the present invention that solves this problem is Carbon particle material having pores with a pore volume of 80% or more in the pore size distribution of 2 to 10 nm in the particles, based on the whole pore volume in the pore size distribution of 1 to 100 nm Partially included Carbon black, activated carbon and / or acetylene black And a catalyst particle supported on the carrier (claim 1).
[0010]
With general carbon materials Carbon particle material having the above particle size distribution The above problem can be solved by using a mixture of and. The above carbon particle material is Mesoporous carbon A kind of Since the pore size distribution is smaller than that of a general carbon material and the particle size distribution is uniform, the dispersibility of the supported catalyst particles is good, and the waste of the catalyst particles supported in the pores can be reduced. Carbon particle material By mixing carbon materials other than Carbon particle material When used alone, it is possible to solve the problem that the diffusibility of the reaction gas is not sufficient, and furthermore, it is possible to efficiently form an electron transfer network and to reduce the internal resistance of the fuel cell.
[0011]
Furthermore, the fuel cell of the present invention that solves the above problems is a solid High molecular A membrane-electrode assembly having an electrolyte membrane and a gas diffusion electrode including the fuel cell electrode catalyst according to any one of the above and sandwiching the solid electrolyte membrane (Claim 2). .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
(Electrocatalyst for fuel cell)
The electrode catalyst for fuel cells of the present invention is Carbon particle material having pores with a pore volume of 80% or more in the pore size distribution of 2 to 10 nm in the particles, based on the whole pore volume in the pore size distribution of 1 to 100 nm Partially included Carbon black, activated carbon and / or acetylene black And a catalyst particle supported on the carrier.
[0013]
The carbon material constituting the carrier is Carbon particle material Including Only , Carbon black, activated carbon And / or Acetylene black With In a mixture Ah The Carbon particle material Since the cohesiveness of the catalyst particles made of Pt or the like supported on the carrier can be suppressed by containing the catalyst, the dispersibility is improved and the catalyst particles can be efficiently used.
[0014]
Carbon particle material Since the pore diameter is small and well controlled, the catalyst particles supported in the pores are hardly wasted. That is, a carbon material having a high specific surface area such as carbon black has relatively large cavities inside the primary particles, and the catalyst particles supported in the cavities cannot contribute to the electrode reaction. Also, Carbon particle material Addition of other carbon materials to a single substance improves gas diffusivity such as fuel gas. When the gas diffusibility is improved, a voltage drop when a large current is taken out from the fuel cell can be suppressed. In particular Carbon particle material When a carbon material composed of a mixture of carbon black and carbon black is used as a support, a high-performance fuel cell electrode catalyst can be provided.
[0015]
Furthermore, the electrode prepared by dispersing the present fuel cell electrode catalyst in a proton conductive material such as Nafion is an electrode whose proton value is efficiently formed and the IR value is lowered, and the details are not clear. Improves water retention inside . Here, in this specification, Charcoal XRD and nitrogen adsorption methods are methods for measuring the pore size distribution of raw materials. It was adopted .
[0016]
here, Carbon particle material The mixing ratio with other carbon materials is not particularly limited, but is preferably in the range of 1: 9 to 9: 1 by mass ratio, particularly preferably 1: 1.
[0017]
The carrier preferably has a particle size distribution having two or more peak values. By mixing particles with different particle diameters, the number of points of physical contact between the electrode catalysts for the fuel cell that are finally produced increases, and the conductive path of the electrons generated by the cell reaction is efficiently formed. As a result, IR becomes small. The ratio of the magnitudes of two or more peak values is 2 or more, more preferably 5 or more. Here, the ratio of the magnitudes of the peak values is a value obtained by dividing the peak value having a large particle diameter out of the two by the other peak value. The particle size distribution of the carrier can be measured by TEM or SEM observation.
[0018]
Especially as a carbon material with a relatively large particle size distribution Carbon particle material By using this, a higher performance electrode catalyst for fuel cells can be obtained. The method of making the particle size distribution of the carbon material have two or more peak values can be achieved by mixing carbon materials having different particle size distributions. When mixing carbon materials having different particle size distributions, mixing may be performed at any time before and after the catalyst particles are supported. Mixing of carbon materials with different particle size distributions (or carbon materials supporting catalyst particles) may be performed by a simple physical method such as milling or mixing them in a proper solvent. Ultrasonic irradiation may be performed for dispersion.
[0019]
Carbon particle material The method for producing is not particularly limited. For example, after adsorbing and impregnating carbon-containing molecules such as sucrose, particularly preferably carbohydrates, to porous particles such as silica and titania having the desired pore distribution (mesoporous), carbon is added under an inert atmosphere. Turn into. Carbohydrates are preferred because the dehydration reaction proceeds easily.
After that, porous particles such as silica are used as a template by dissolving and removing particles that have become a template such as silica with hydrofluoric acid or NaOH / EtOH. Carbon particle material Can be manufactured. For example, silica mesoporous MCM-48 can be used as a porous particle as a template.
[0020]
The catalyst particles supported on the carrier are not particularly limited. For example, noble metal elements such as platinum, ruthenium, palladium, osmium, iridium, rhodium, gold and silver, base metal elements such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo and W Can be included. The mass ratio between the support and the catalyst particles is not particularly limited, but can be about 5% to 80%.
[0021]
The method for supporting the catalyst particles on the carrier is not particularly limited, and a known method and an improved method thereof can be applied. For example, (1) a carrier is brought into contact with a solution containing ions of elements constituting the catalyst particles (Pt, etc.), and the ions of those elements are adsorbed on the carrier, and then the carrier on which the ions are adsorbed is reduced in a reducing atmosphere. A method of reducing the ions adsorbed on the support held below to the original metal such as Pt to form catalyst particles, and (2) immersing the support in a solution containing the ions of these elements, There are a method of directly supporting catalyst particles on the support by reducing ions, and a method of supporting the metal elements constituting the catalyst particles directly on the support by a physical method.
[0022]
Specifically, in the method (1), a catalyst particle made of metal is formed by impregnating a carrier with a cation of a metal element constituting the catalyst particle and reducing the cation of the metal element impregnated on the carrier. A reduction process. In the impregnation step, after immersing the support in a solution containing cations, the evaporating / drying method of drying the solvent of the immersed solution and adsorbing the cation in the solution on the support until the adsorption to the support is in an equilibrium state. An equilibrium adsorption method or a spray method in which a solution containing a cation is directly sprayed and dried on a carrier can be employed. In the reduction step, the carrier on which the cation is adsorbed is brought into contact with a reducing gas such as hydrogen gas to reduce the cation to a metal. In this case, the reduction reaction in which the cation is reduced to the metal proceeds efficiently by having a heating step of heating the carrier. Specifically, after drying the support impregnated with the cation, hydrogen gas phase reduction is performed at about 100 to 800 ° C. for about 1 to 4 hours (calcination in a tubular furnace or the like in which hydrogen is flown). The cation can be reduced to a metal, and a metal having catalytic activity can be supported on the carrier.
[0023]
Specifically, the method (2) is a method in which the fine particles are deposited and supported on the support by immersing the support in a solution containing a cation of the metal element constituting the catalyst particles and then reducing the cation. is there. As a method of reducing cations, there are a chemical method of adding a reducing agent, a physical method of reducing by heating a solution, a method of combining both, and the like.
[0024]
Further, before mixing the reducing agent, it is preferable to deposit water in a solution containing a cation of a metal element to precipitate oxide fine particles such as Pt. For example, when a hexahydroxo Pt nitric acid solution is used as a Pt precursor (solution containing Pt cation), nitric acid is hydrolyzed by adding water to produce colloidal particles of Pt oxide, and fine particles are formed. It is formed. In addition to (or in place of) water, an acid such as nitric acid or acetic acid, or an organic solvent such as alcohol, acetone or chloroform improves the dispersibility of a carrier such as carbon powder or produces a metal It is preferable because the particle diameter of the oxide fine particles can be controlled.
[0025]
It does not specifically limit as a reducing agent, A normal reducing agent can be used in a normal quantity. For example, hydrides such as sodium borohydride, hydrogen, nonmetallic ions or acids (formic acid (soda), etc.), alcohols such as ethanol, lower oxides and lower oxygen salts, aldehydes such as hydrazine, formaldehyde and the like. Of these, alcohol, formic acid, hydrazine and the like can be rapidly reduced after being added as a reducing agent and further heated. Thus, the support | carrier which carry | supported the metal is filtered, dried, etc. May have a heating step to dry quickly.
[0026]
Examples of the solution containing cations used in the methods (1) and (2). Examples of a solution containing a cation of Pt among metal elements constituting the catalyst particles are hexahydroxo Pt sulfite solution, dinitrodiamino Pt sulfite solution, hexahydroxo Pt sulfite solution, divalent Pt ammine solution, and tetravalent Pt ammine solution. And Pt ammine solution, and a sulfite Pt solution.
[0027]
Furthermore, when a plurality of metal elements are supported on the support, catalyst particles can be obtained by having a heating step of heating and alloying the elements supported on the support in this way. The heating step in alloying is not particularly limited, and may be performed by a method usually used for alloying.
[0028]
(Fuel cell)
The fuel cell of this embodiment is PEFC. As the fuel cell of this embodiment, a stack in which fuel cells are singly or plurally stacked is formed. Fuel cell is solid High molecular An electrolyte membrane and a solid containing the fuel cell electrode catalyst described above High molecular A membrane-electrode assembly (MEA) having a gas diffusion electrode for sandwiching an electrolyte membrane is provided, and the MEA is sandwiched by a separator.
[0029]
The solid electrolyte membrane is not particularly limited, and a general solid polymer electrolyte membrane (perfluorosulfonic acid resin) such as Nafion can be used. The gas diffusion electrode is a membrane in which the fuel cell electrode catalyst is bound by a solid electrolyte. It can be formed by mixing a fuel cell electrode catalyst and a solid electrolyte membrane on both sides of the solid electrolyte membrane and applying paste-like ink with an appropriate solvent. The gas diffusion electrode of the present fuel cell includes the fuel cell electrode catalyst of the present invention, and is particularly preferably applied to the cathode.
[0030]
Gas supply devices for supplying fuel gas and oxidant gas to the reaction electrodes on both sides of the polymer electrolyte membrane are connected from the corresponding separators. As the fuel gas, air is defined for convenience, using hydrogen gas as an oxidant gas. The MEA can be further sandwiched between both sides by a diffusion layer.
[0031]
For the diffusion layer, for example, a mixture of general carbon powder and water-repellent polymer powder can be used. It can also be formed by containing a solid electrolyte.
[0032]
The separator can also use the material and form generally used. A flow path is formed in the separator, and a gas supply device for supplying a reaction gas is connected to the flow path, and at the same time, a means for removing the non-reacted reaction gas and generated water is connected. .
[0033]
【Example】
( Carbon particle material Preparation)
-Preparation of MCM-48
Carbon particle material Cubic-type silica mesoporous material (MCM-48) used as a template of [R. Ryo, S .; H. Joe, and J.A. M.M. Kim, J. et al. Phys. Chem. B103, 7435 (1999)].
[0034]
Silica gel powder (Wakogel Q-63: Wako Pure Chemical Industries) and sodium hydroxide were mixed at a molar ratio of silica: sodium hydroxide: water = 1: 2: 30 to obtain an aqueous sodium silicate solution. In order to promote dissolution of the silica gel powder, the mixture was heated and stirred in a warm water bath at 80 ° C. to obtain a substantially transparent solution. This was left tightly sealed in a polypropylene container at room temperature for 1 week to obtain a completely uniform transparent solution.
[0035]
Hexadecyltrimethylammonium bromide (C ₁₆ H ₃₃ N (CH _Three ) _Three Br) 12.4 g and Brij30 (C ₁₂ H _{twenty five} (OCH ₂ CH ₂ ) _Four A solution obtained by heating and dissolving 2.2 g of OH in 169.4 g of water was added to the above-mentioned aqueous sodium silicate solution (133.76 g), and then immediately sealed and mixed with shaking vigorously. The composition of the mixture is a mixed solution in a molar ratio of silica: hexadecyltrimethylammonium bromide: Brij30: sodium hydroxide: water = 5.0: 0.85: 0.15: 2.5: 400.
[0036]
This mixed solution was allowed to stand in a constant temperature layer at 100 ° C. for 2 days, and then 3.5 g of acetic acid was added dropwise to the mixed solution with stirring. Thereafter, the product left in a constant temperature layer at 100 ° C. was subjected to hot filtration, and then dissolved sodium ions were washed with ion-exchanged water. This was dried at 100 ° C. and calcined at 550 ° C. for 6 hours to obtain a Cubic type silica mesoporous material (MCM-48).
[0037]
・ Carbon particle material Preparation of
Carbon particle material Was prepared almost according to the method described in the literature [R. Ryo, S .; H. Joe, and S.J. Jun, J. et al. Phys. Chem. B103, 10670 (1999)].
[0038]
12.5 g of sucrose and 1.4 g of concentrated sulfuric acid are dissolved in 60 g of water, and after mixing this solution with 10 g of MCM-48 powder in a dry state, sucrose is allowed to stand at room temperature for 12 hours to obtain sucrose. It was impregnated and adsorbed in the pores of 48 particles. After the wet sample was dried at 100 ° C., the temperature was raised to 160 ° C. and a part of sucrose was dehydrated and carbonized. Further, the previous sample was mixed in a solution obtained by dissolving 12.5 g of sucrose and 0.7 g of concentrated sulfuric acid in 60 g of water, and left for 12 hours. After the wet sample was dried at 100 ° C., the temperature was raised to 160 ° C. to dehydrate and carbonize sucrose. The organic matter in the pores was completely carbonized by further heating at 900 ° C. in a nitrogen stream using a tubular furnace.
[0039]
The silica skeleton derived from the MCM-48 powder used as a mold was dissolved and removed with hydrofluoric acid. Specifically, the silica skeleton was dissolved and removed by immersing the sample in a mixed solution of 46% aqueous hydrofluoric acid and ethanol (volume ratio of 1: 1) at room temperature for 12 hours. This was separated by filtration and washed with a water-ethanol mixed solvent (volume ratio 1: 1). Again, air-dry the filtered powder after dispersion in a water-ethanol mixed solvent at room temperature. Carbon particle material Got.
[0040]
・ Carbon particle material Properties of
By XRD measurement and nitrogen adsorption measurement, Carbon particle material The properties of were examined. XRD measurement used RINT2200 made by Rigaku Denki, and CuKα was used as a radiation source. Nitrogen adsorption measurement was performed at a measurement temperature of 77.4K using AUTOSORB-1 manufactured by Quantachrome. Also, Carbon particle material And the particle size distribution of carbon black was measured by a TEM observation photograph.
[0041]
The results are shown in FIG. 1 (XRD) and FIG. 2 (nitrogen adsorption measurement). As is clear from FIG. 1, a peak based on the presence of periodic pores was observed. From the result of FIG. 2, the specific surface area is 1835 m. ² / G (BET analysis), the pore volume was 0.92 mL / g (αs analysis), and the average pore diameter was 2.9 nm (αs analysis). The pore size distribution is shown in FIG. FIG. 4 shows the pore size distribution of carbon black.
[0042]
Carbon particle material There are almost no pores of 10 nm or more, and the distribution is concentrated at 2 to 3 nm. Carbon black has uniform pores in the measured pore size distribution.
[0043]
3 and 4 also show the pore size distribution after Pt as catalyst particles is supported on each carbon material. A method for supporting Pt will be described later. Further, the abundance ratio of the pores is normalized per mass of the carbon material. From the results of pore size distribution after Pt loading, Carbon particle material The pores concentrated at 2 to 3 nm are greatly reduced, and it can be inferred that Pt fine particles were supported in the 2 to 3 nm pores existing from the beginning.
[0044]
・ Supporting catalyst particles on the carrier
The above Carbon particle material And about carbon black, it was set as the carbon dispersion liquid which was separately disperse | distributed 40g at a time in 10L of water. A 2 mol / L sulfuric acid aqueous solution of sulfite-based platinum containing 60 g of platinum was added to the carbon dispersion and stirred well.
[0045]
To each dispersion, 2 L of 30% hydrogen peroxide aqueous solution was added over 10 hours with stirring. Then, it heated to 95-100 degreeC and hold | maintained at the temperature for 2 hours.
After cooling to room temperature, the dispersion was collected by filtration. The filtrate was washed with distilled water until the pH of the filtrate reached 5. The product collected by filtration was vacuum-dried at 100 ° C. for 6 hours. Carbon particle material And Pt as catalyst particles were supported on carbon black and carbon black, respectively. The amount of Pt supported was 60% by mass with respect to the whole.
[0046]
(Fuel cell creation)
As carrier Carbon particle material A fuel cell electrode catalyst having catalyst particles supported thereon and a fuel cell electrode catalyst having catalyst particles supported on carbon black as a carrier were mixed at a mass ratio of 1: 1. Both electrode catalysts for fuel cells were mixed by shaking in a closed container. As a carbon material by mixing both Carbon particle material And the electrode catalyst for fuel cells of this invention which has carbon black as a support | carrier was obtained.
[0047]
As a result, the fuel cell electrode catalyst (sample 1) of the present invention is used as a carrier. Carbon particle material There were obtained three types of fuel cell electrode catalysts: a fuel cell electrode catalyst (sample 2) using a single catalyst and a fuel cell electrode catalyst (sample 3) using carbon black alone as a carrier.
[0048]
A fuel cell was prepared using these three types of fuel cell electrode catalysts. First, an electrode catalyst for a fuel cell is dispersed by using a solid polymer electrolyte alcoholic solution (NafionSE-20092) at a mass ratio of Nafion to carbon of 0.75: 1. It was applied to a transfer film made of Teflon (trademark), dried, and bonded to a solid electrolyte membrane (Gore 40 μm: Japan Gore-Tex) by thermal transfer to fix a gas diffusion electrode to obtain MEA. This is a method generally known as the Decal method. The manufactured MEA was sandwiched between separators to produce a single cell.
[0049]
(Evaluation test)
Fuel Cell Using Sample 1 Fuel Cell Electrode Catalyst (Example 1), Fuel Cell Using Sample 2 Fuel Cell Electrode Catalyst (Comparative Example 1), and Fuel Using Sample 3 Fuel Cell Electrode Catalyst The battery (Comparative Example 2) was subjected to power generation evaluation and AC impedance measurement. In the fuel cell of Example 1, the amount of the cathode fuel cell electrode catalyst is 0.422 mg / cm in terms of Pt. ² The anode is 0.368 mg / cm ² In the fuel cell of Comparative Example 1, the cathode is 0.369 mg / cm. ² The anode is 0.362 mg / cm ² In the fuel cell of Comparative Example 2, the cathode is 0.425 mg / cm. ² The anode is 0.372 mg / cm ² Met.
[0050]
The power generation conditions are such that hydrogen gas is supplied to the anode side at a humidification temperature of 85 ° C. so that the pressure is 500 mL / min and 0.1 MPa, and air is supplied to the cathode side at a humidification temperature of 70 ° C. so that the pressure is 1000 mL / min and 0.1 MPa. Supplied to. In power generation evaluation and AC impedance measurement, voltage change and IR change were measured when the current passed through the load was changed. The results are shown in FIGS.
[0051]
Compared to the fuel cells of Example 1 and Comparative Example 2, the fuel cell of Comparative Example 1 has a large voltage drop in the high current region. Since the value of IR is smaller than the fuel cell of Comparative Example 2, Carbon particle material It suggests that the gas diffusivity of the fuel cell electrode catalyst of Sample 2 consisting of a single sample is not sufficient. Carbon particle material Assuming that the gas diffusivity alone is not enough, (1) Carbon particle material Is a low structure and the gas diffusion channel is not formed efficiently, (2) Carbon particle material Has almost no pores of 10 nm or more which are considered to have a positive effect on gas diffusivity, and a solid polymer electrolyte membrane showing a particle size distribution of 10 nm or more cannot enter mesopores. Therefore, when the solid polymer electrolyte is added at the same mass ratio with respect to carbon, the solid polymer electrolyte for connecting the fuel cell electrode catalysts in the comparative example becomes excessive. For this reason, the proton conductivity is improved and the IR is reduced, but the gas diffusion channel is inhibited by the solid polymer electrolyte.
[0052]
The fuel cell of Example 1 has a smaller IR value by 1.5 to 2.5 mΩ than the fuel cell of Comparative Example 2. In addition, compared with the fuel cells of Comparative Examples 1 and 2, a unique profile is shown on the low current side. The IR value of the fuel cells of Comparative Examples 1 and 2 increases on the low current side because the water produced by the reaction decreases compared to the high current side, and the solid polymer electrolyte becomes slightly dry. It can be inferred. Therefore, it is considered that the fuel cell of Example 1 is less influenced by drying or difficult to dry on the low current side.
[0053]
In summary, the fuel cell of Example 1, that is, Carbon particle material A fuel cell using an electrode catalyst for a fuel cell using a carbon material comprising a mixture of carbon black and carbon black as a carrier is (1) Carbon particle material As in the fuel cell of Comparative Example 1 used alone, the gas diffusivity is not significantly impaired, (2) the proton conductive path is efficiently formed by the solid polymer electrolyte, and (3) the water retention is improved. (4) There is an advantage that the value of IR decreases as a whole. Due to the difference in the IR value, the terminal voltage of the fuel cell of Example 1 is 10 mV higher than the fuel cell of Comparative Example 2 in the medium current amount region (0.5 A / cm 2).
[0054]
In addition, using three types of fuel cell electrode catalysts, the dependence of the terminal voltage and IR value on the amount of Pt (the amount of fuel cell electrode catalyst used in the electrodes) was examined. Although details are not shown, for all fuel cell electrode catalysts, the terminal voltage increased as the amount of Pt increased. In the fuel cell of Example 1, the IR value decreased as the Pt amount increased, whereas in the fuel cells of Comparative Examples 1 and 2, the IR value increased as the Pt amount increased. When the thickness of the gas diffusion electrode is about 2 to 3 μm, the sample 1 used in Example 1 has an IR with substantially the same value as Comparative Examples 1 and 2. When the thickness of the gas diffusion electrode is more than that, the IR value of Example 1 is 1.5 to 2 mΩ smaller than those of Comparative Examples 1 and 2. This is presumed to be due to the effect of reducing proton and electron transfer resistance by mixing mesoporous carbon and other carbon materials as the gas diffusion electrode becomes thicker. In Samples 2 and 3 used in Comparative Examples 1 and 2, it is considered that the migration resistance of protons and electrons increases as the gas diffusion electrode applied to the solid polymer electrolyte membrane becomes thicker.
[0055]
(Observation of MEA)
For the MEAs used in the fuel cells of Example 1 and Comparative Examples 1 and 2, the cross section in the direction perpendicular to the membrane was observed with a transmission electron microscope (TEM). The results are shown in FIGS. The part that is particularly black in the TEM photograph is Pt.
[0056]
8 to 10 are those of Comparative Example 2 (carbon black). The observation magnification is increased from FIG. 8 to FIG.
[0057]
11 to 13 show Comparative Example 1 ( Carbon particle material )belongs to. The magnification increases as it becomes from FIG. 11 and 12, a large black portion is recognized and Pt aggregation is suspected, but according to FIG. 13 having a higher magnification, Pt that appears to be aggregated is also finely dispersed with a size of several nm. You can see that However, Carbon particle material The contact between them is not very close.
[0058]
14 to 16 show Example 1 (carbon black and Carbon particle material And a mixture thereof. As shown in FIGS. 14 to 16, the magnification increases. From the figure, the combined properties of Comparative Example 1 and Comparative Example 2 can be estimated. That is, in some places, aggregation of Pt is recognized and Pt is dispersed in a very small size. Also, the contact between the particles is very close. However, Pt aggregation is as small as about 100 nm to 200 nm, and it can be estimated that Pt can be used effectively.
[0059]
Carbon particle material In some cases, a large amount of Pt is supported on a part of the particles supporting Pt, and there is a possibility that the utilization efficiency of Pt is not sufficient. Therefore, Pt utilization efficiency can be improved by reducing the amount of Pt supported in the future. Carbon particle material On the other hand, it can be presumed that a fuel cell electrode catalyst that exhibits higher performance can be provided with a smaller amount of supported Pt.
[Brief description of the drawings]
FIG. 1 shows an example. Carbon particle material This is an XRD spectrum.
FIG. 2 in the embodiment Carbon particle material It is the graph which showed the result of nitrogen adsorption measurement of.
FIG. 3 in the embodiment Carbon particle material It is the graph which showed the pore diameter distribution.
FIG. 4 is a graph showing the pore size distribution of carbon black in Examples.
FIG. 5 is a graph showing the results of a power generation test of each fuel cell of Example 1 and Comparative Examples 1 and 2.
6 is a graph showing the current density dependence of IR of each fuel cell of Example 1 and Comparative Examples 1 and 2. FIG.
7 is a partially enlarged view of FIG. 5;
8 is a TEM photograph of an MEA cross section of a fuel cell of Comparative Example 2. FIG.
9 is a TEM photograph of an MEA cross section of a fuel cell of Comparative Example 2. FIG.
10 is a TEM photograph of an MEA cross section of a fuel cell of Comparative Example 2. FIG.
11 is a TEM photograph of an MEA cross section of a fuel cell of Comparative Example 1. FIG.
12 is a TEM photograph of an MEA cross section of the fuel cell of Comparative Example 1. FIG.
13 is a TEM photograph of an MEA cross section of the fuel cell of Comparative Example 1. FIG.
14 is a TEM photograph of an MEA cross section of the fuel cell of Example 1. FIG.
15 is a TEM photograph of an MEA cross section of the fuel cell of Example 1. FIG.
16 is a TEM photograph of an MEA cross section of the fuel cell of Example 1. FIG.

Claims (2)

Based on the total pore volume in the pore size distribution of 1 to 100 nm, viewed contains a portion of carbon particulate material having a pore pore volume is 80% or more in the pore size distribution of the 2~10nm in the particle , carbon black, activated carbon and / or a carrier consisting of acetylene black from including carbon material, fuel cell electrode catalyst of the catalyst particles supported on the carrier, characterized in that it has a. A fuel cell comprising a membrane-electrode assembly having a solid polymer electrolyte membrane and a gas diffusion electrode containing the fuel cell electrode catalyst according to claim 1 and sandwiching the solid electrolyte membrane.

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