WO2011074327A1 - Gas diffusion layer for fuel cell, and membrane electrode assembly using said gas diffusion layer for fuel cell - Google Patents

Gas diffusion layer for fuel cell, and membrane electrode assembly using said gas diffusion layer for fuel cell Download PDF

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WO2011074327A1
WO2011074327A1 PCT/JP2010/068849 JP2010068849W WO2011074327A1 WO 2011074327 A1 WO2011074327 A1 WO 2011074327A1 JP 2010068849 W JP2010068849 W JP 2010068849W WO 2011074327 A1 WO2011074327 A1 WO 2011074327A1
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gas diffusion
diffusion layer
fuel cell
graphite
layer
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PCT/JP2010/068849
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French (fr)
Japanese (ja)
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陽三 奥山
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日産自動車株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/96—Carbon-based electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8605—Porous electrodes
    • H01M4/861—Porous electrodes with a gradient in the porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M2008/1095—Fuel cells with polymeric electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention relates to a gas diffusion layer (GDL: Gas Diffusion Layer) used in a polymer electrolyte fuel cell (PEFC) and a membrane electrode assembly (MEA: Membrane Electrode Assembly) using the same.
  • GDL Gas Diffusion Layer
  • PEFC polymer electrolyte fuel cell
  • MEA Membrane Electrode Assembly
  • a polymer electrolyte fuel cell using a proton conductive solid polymer membrane operates at a lower temperature than other types of fuel cells, such as solid oxide fuel cells and molten carbonate fuel cells. It is also expected to be used as a power source for moving bodies such as automobiles, and its practical use has begun.
  • a gas diffusion electrode used for a polymer electrolyte fuel cell includes an electrode catalyst layer containing catalyst-supported carbon fine particles coated with an ion exchange resin (polymer electrolyte) of the same type or different type from a polymer electrolyte membrane, and the catalyst. It comprises a gas diffusion layer for supplying a reaction gas to the layer and collecting charges generated in the catalyst layer. And the membrane electrode assembly is formed by joining the electrode catalyst layer side of such a gas diffusion electrode in a state of facing the polymer electrolyte membrane, and a plurality of the membrane electrode assemblies are connected to the gas flow path.
  • a fuel cell is configured by stacking the separators provided.
  • the gas diffusion layer is generally made of carbon paper, woven fabric, or non-woven fabric made using carbon fibers.
  • the gas diffusion layer used in such a polymer electrolyte fuel cell, is used as an intermediate layer for reducing the electric resistance between the gas diffusion layer and the catalyst layer and improving the gas flow.
  • a catalyst having a fine porous layer mainly composed of a conductive material such as a carbon material is known on the catalyst layer side. By providing such a fine porous layer on the catalyst layer side of the gas diffusion layer, even if there is a whirling in the carbon fiber that constitutes the gas diffusion layer, it is possible that this will break through the electrolyte membrane.
  • the fine porous layer also functions as a protective layer for the electrolyte membrane.
  • a gas diffusion layer that can adjust the water repellency and drainage on the membrane side in order to cope with flooding and excessive drying
  • a gas diffusion layer has been proposed that includes a coating layer having a flaky conductive material, a powdered conductive material, and a water repellent and having active material permeability and conductivity.
  • a coating composition containing a flaky conductive material, a powdered conductive material, and a water repellent is applied to the surface of the porous substrate. (See Patent Document 1).
  • the above-described fine porous film and coating layer constitute part of the gas diffusion layer, and as long as the gas diffusion layer is questioned about overall conductivity and gas diffusivity, these fine porous film and coating layer It goes without saying that the coating layer is required to have excellent gas diffusibility as well as conductivity. However, these electrical conductivity and gas diffusivity are generally in a trade-off relationship. When an attempt is made to improve the diffusibility by increasing the porosity of the layer, the electrical resistance increases. There is a problem that it is extremely difficult to achieve both of these because it is necessary to form an organization and results in deterioration of diffusibility.
  • the present invention has been made by paying attention to the above problems in a polymer electrolyte fuel cell having a gas diffusion layer provided with a layer containing a conductive substance.
  • the purpose of the gas diffusion layer which can achieve both low resistance and high diffusion of the gas diffusion layer, which is usually in a trade-off relationship, contributes to the improvement of the performance of the polymer electrolyte fuel cell.
  • An object of the present invention is to provide a membrane electrode assembly using such a gas diffusion layer.
  • the inventor of the present invention has achieved a fine porous layer containing scaly graphite and a conductive path material. It has been found that the above object can be achieved by providing the present invention, and the present invention has been completed.
  • the present invention is based on the above knowledge, and the fuel cell gas diffusion layer of the present invention is disposed adjacent to the catalyst layer in the membrane electrode assembly for a polymer electrolyte fuel cell.
  • the membrane electrode assembly for a polymer electrolyte fuel cell of the present invention is characterized in that the gas diffusion layer of the present invention is laminated on both surfaces of an electrolyte membrane via a catalyst layer.
  • the gas diffusion layer of the present invention is manufactured by a wet method, an ink having a viscosity of 1000 to 10,000 mPa ⁇ s at a shear rate of 100 / s is applied to a porous substrate that has been subjected to a water repellent treatment. It is characterized by that.
  • the fine porous layer in the gas diffusion layer includes scaly graphite and a conductive path material having an average particle size smaller than this and contributing to electrical connection between scaly graphites. Therefore, it is possible to achieve both low resistance and high diffusion in the gas diffusion layer.
  • FIG. 2 is an enlarged schematic view (a) schematically showing the structure of a fine porous layer constituting a part of the gas diffusion layer for a fuel cell of the present invention, and a plan view showing the shape of scaly graphite constituting the fine porous layer. It is (b) and a side view (c). It is a schematic sectional drawing which shows the further another example of the membrane electrode assembly using the gas diffusion layer for fuel cells of this invention.
  • GDL fuel cell gas diffusion layer
  • MEA membrane electrode assembly
  • the GDL for a fuel cell according to the present invention includes a fine porous layer (hereinafter abbreviated as “MPL (Micro Porous Layer)”) containing scaly graphite and a conductive path material, and the scale in the MPL.
  • MPL Micro Porous Layer
  • the average particle size of the graphite is larger than the average particle size of the conductive path material.
  • the contact area between the graphite particles decreases, and the electrical resistance in the thickness direction of the MPL increases.
  • a conductive path material having an average particle size smaller than this is mixed to form MPL, so that the contact area between the graphite particles increases through the path material. Will do. That is, even when the pore size is increased by using scaly graphite and the diffusion is high, the contact area between the graphite particles increases due to the presence of the conductive path material, and the electrical resistance decreases.
  • the MPL made of it is possible to achieve both low resistance and high diffusion in the gas diffusion layer.
  • FIG. 1 An example of the structure of an MEA using the GDL for a fuel cell of the present invention is shown in FIG.
  • the catalyst layer (20), the MPL (31), and the GDL base material (32) are respectively disposed on the anode and cathode both centered on the electrolyte membrane (10).
  • GDL (30) is comprised by (31) and GDL base material (32).
  • the GDL (30) is composed of the GDL base material (32) and the MPL (31).
  • the GDL base material (32) it is not always necessary to use the GDL base material (32), as shown in FIG.
  • the MEA (1) including the GDL (30) made only of the MPL (31) can be used, and this enables the fuel cell to be thinned and miniaturized.
  • a hydrocarbon electrolyte membrane in addition to a perfluorosulfonic acid electrolyte membrane that is generally used, a hydrocarbon electrolyte membrane can also be used.
  • platinum or a platinum alloy supported on carbon carbon black such as oil furnace black, acetylene black, thermal black, channel black, ketjen black, graphite, activated carbon, etc. It is formed by mixing a fluorosulfonic acid electrolyte solution or a hydrocarbon electrolyte solution.
  • a water repellent and a pore increasing agent it is also possible to add a water repellent and a pore increasing agent as needed.
  • the MPL (31) forming a part of the GDL (30) is composed of scale-like graphite (35), a conductive path material (36), and PTFE as a binder and water repellent. Often composed of (polytetrafluoroethylene) or the like, the scaly graphite (35) often exists in a state along the surface direction of the MPL (31).
  • the thickness of the MPL (31) is preferably in the range of 10 to 100 ⁇ m.
  • the conductive path material (36) for example, carbon black such as oil furnace black, acetylene black, thermal black, channel black, graphite (natural graphite (flaky, massive, earthy)), artificial graphite, expanded Graphite), carbon fiber, and the like can be used. It is also possible to use a mixture of these plural types.
  • the use of a commercially available material such as carbon black, graphite, or carbon fiber as the conductive path material can prevent an increase in cost.
  • acetylene black as the carbon black, the dispersibility of the carbon particles is improved and the productivity is improved.
  • the average particle diameter of the conductive path material (36) is preferably 10 nm to 5 ⁇ m.
  • the flaky graphite (35) has a high crystallinity and has a scaly shape with a high aspect ratio (plane diameter D / thickness H) as shown in FIGS. 2 (b) and (c).
  • the flaky graphite means one having a thickness H of 0.05 to 0.3 ⁇ m and an aspect ratio of about 30 to 300.
  • the average particle diameter (average of planar diameter) of the flake graphite (35) is preferably 5 to 50 ⁇ m. If it is smaller than 5 ⁇ m, it cannot contribute to high diffusion, and if it exceeds 50 ⁇ m, the effect of the conductive path material is reduced.
  • the conductive path material has a low resistance function and the scale graphite has a high diffusion function. From the viewpoint of ensuring compatibility, it is desirable that the average particle diameter of the conductive path material is 0.02 to 80% of the scaly graphite, and more preferably within the range of 0.1 to 35%. More desirable.
  • the average particle size of the scaly graphite (35) is preferably 5 to 500% of the thickness of the MPL (31).
  • the thickness of MPL (31) is about 10 to 100 ⁇ m as described above.
  • the average particle size of the flake graphite is less than 5% of the MPL thickness, high diffusion can be achieved.
  • it exceeds 500% the conductivity tends to deteriorate, so that it is difficult to achieve both of these characteristics.
  • the content in the MPL is preferably 5 to 30% (mass ratio) from the viewpoint of ensuring both low resistance and high diffusion more reliably. . That is, when the content of carbon black is less than 5%, the contact area cannot be obtained and the resistance does not decrease. On the other hand, when the content exceeds 30%, the small particle diameter fills the pores, so that the diffusibility deteriorates. . It is also desirable to use carbon black having a specific surface area of 1000 m 2 / g or more, which can further reduce the resistance.
  • the thermal resistance is lowered and the low humidification performance is improved.
  • graphite having an average particle size of 3 ⁇ m or more in order for this to function as a conductive path material, it is necessary to add more graphite compared to carbon black or the like having a small particle size, and the content in MPL 30% (mass ratio) or more is required.
  • graphite having an average particle size of 3 ⁇ m or more has a large particle size, and even if the mixing amount is increased, the diffusivity does not deteriorate so much, so flake graphite is mixed and the necessary amount as a binder is included.
  • the graphite content As long as there is no particular upper limit to the graphite content as the conductive path material.
  • the resistance decreases even with a small blending ratio similar to that of carbon black, and the upper limit value needs to be set to about 50% from the viewpoint of ensuring diffusibility.
  • the GDL substrate is made of a material formed of carbon fibers such as carbon paper, carbon cloth, and nonwoven fabric.
  • a water repellent impregnated with PTFE or the like is used.
  • the substrate may not be subjected to water repellent treatment or may be subjected to hydrophilic treatment.
  • the GDL substrate may be impregnated with graphite, carbon black, or a mixture thereof.
  • the viscosity at a shear rate of 100 / s is 1000 to 10000 mPas on the porous substrate subjected to the water repellent treatment as described above. It is preferable to apply s ink. That is, when the viscosity is less than 1000 mPa ⁇ s, the ink penetration into the porous substrate made of carbon paper or the like increases, and the gas permeability of the gas diffusion layer tends to decrease. On the other hand, when it exceeds 10,000 mPa ⁇ s, although the ink does not enter the base material, it becomes difficult to apply the ink to a uniform thickness, and lump or bubbles may be easily generated on the surface.
  • the viscosity of the ink can be adjusted, for example, by increasing or decreasing the amount of thickening agent such as polyacrylic acid or polyether.
  • a membrane electrode assembly (MEA) for a polymer electrolyte fuel cell according to the present invention is obtained by laminating the GDL (30) on both surfaces of the electrolyte membrane (10) via a catalyst layer (20). Since (30) is compatible with conductivity and diffusivity, high power generation performance can be exhibited.
  • the GDL (30) is bonded to the electrolyte membrane (10) which is transferred or directly coated with the catalyst layer (20) by hot pressing, and the GDL (consisting of MPL and GDL base material).
  • the catalyst layer (20) previously applied to the MPL side may be joined to the electrolyte membrane (1) by hot pressing, either of which may be used.
  • the average particle size of the flaky graphite on the anode side smaller than that on the cathode side, thereby reducing the diffusibility of the anode. Since the diffusibility of the cathode is improved, both the low humidification performance and the high humidification performance are improved.
  • carbon black having a specific surface area of 1000 m 2 / g or more is used as the conductive path material, it is desirable to use it at least on the anode side. That is, since such carbon black has improved water vapor adsorption, low humidification performance can be improved by using it for the anode.
  • the above-mentioned carbon black having a specific surface area of 1000 m 2 / g or more is contained on the cathode side in such a way that it is more on the dry side and less on the wet side, thereby reducing the humidification performance and the high humidification performance. Both can be improved.
  • the dry side and the wet side in the cathode surface when the flow direction of the cathode gas and the cooling water is a counter flow, the cathode inlet is the dry side and the cathode outlet is the wet side.
  • the cathode inlet is on the wet side and the cathode outlet is on the dry side.
  • the MPL (31) of the gas diffusion layer (30) as shown in FIG. 1 is not limited to the arrangement on the catalyst layer (20) side, but as shown in FIG. It is also possible to add the MPL (31) of the gas diffusion layer (30) to the catalyst layer (20) side and arrange it on the separator side, that is, on the opposite side of the electrolyte membrane.
  • Invention Example 4 By replacing the flake graphite with one having an average particle diameter D50 of 6 ⁇ m and applying MPL ink having a viscosity of 4000 mPa ⁇ s, the same operation as in Invention Example 1 was repeated, thereby repeating the invention example. 4 GDLs were obtained.
  • the MPL basis weight was 30 g / m 2 and the MPL thickness was 20 ⁇ m.
  • Example 1 Example 1 except that MPL ink containing acetylene black and PTFE at a ratio (mass ratio) of 8: 2 and having a viscosity of 2000 mPa ⁇ s was applied without blending scale-like graphite. By repeating the same operation, the GDL of Comparative Example 1 was obtained.
  • the MPL basis weight was 27 g / m 2 and the MPL thickness was 20 ⁇ m.
  • Comparative Example 2 Other than having applied the MPL ink which contains the said scaly graphite and PTFE in the ratio (mass ratio) of 8: 2, and the said viscosity is 2000 mPa * s, without mix
  • the GDL of Comparative Example 2 was obtained.
  • the MPL basis weight was 20 g / m 2 and the MPL thickness was 20 ⁇ m.
  • the ink having a viscosity of 2000 to 4000 mPa ⁇ s at a shear rate of 100 / s is used.
  • the water repellent treatment is applied to the GDL base material in advance.
  • the MPL ink of Example 1 was applied to the GDL substrate without performing the water repellent treatment, the ink penetration depth was about twice that of the case where the water repellent treatment was performed. Has been confirmed to increase.
  • Table 1 shows the measurement results of the electrical resistance in the thickness direction of the GDLs obtained by the above invention examples and comparative examples.
  • both sides of GDL having an area of 0.95 cm 2 were sandwiched between gold foils, and measurement was performed by applying current in a state where a load was applied.
  • the current value was 1 A, up to 5 MPa was taken as one cycle, and the value at 1 MPa in the second cycle was compared.
  • the electrical resistance value in Table 1 it showed with the relative value which set the measured value of the comparative example 2 (no conductive path material) to "1".
  • the resistance value of the invention example including the conductive path material in addition to the flaky graphite is low, and in particular, carbon black having a specific surface area of 1000 m 2 / g or more is used.
  • a resistance value lower than that of Example 1 in which acetylene black having a specific surface area of 40 m 2 / g was used was confirmed.
  • the gas permeability of the invention example including the conductive path material in addition to the flaky graphite is lower than the comparative example 2 not including the conductive path material (the Gurley value is increased), The gas permeability is sufficiently high (the Gurley value is low) compared to Comparative Example 1 that does not contain scale-like graphite.
  • GDL of Invention Example 2 using carbon black having a specific surface area of 1000 m 2 / g or more is affected by deterioration of dispersibility as compared with acetylene black, and gas permeation from Invention Example 1 even with a small content.
  • the gas permeability is sufficiently high (the Gurley value is low) as compared with Comparative Example 1 that does not contain flake graphite.
  • FIG. 5 shows the results of power generation evaluation at 2 A / cm 2 when the relative humidity of the anode and cathode is 30% RH and 20% RH (drying conditions), respectively, and the relative humidity of the anode and cathode is 90% RH.
  • FIG. 6 shows the results of power generation evaluation at 2 A / cm 2 in the case of (wet conditions).
  • the cell voltage (vertical axis) in the figure is shown as a relative value when the value of MEA using GDL of Comparative Example 1 not containing scale-like graphite is “1”.
  • the GDL of Invention Example 1 contains acetylene black having a small particle diameter, but only contains scaly graphite and PTFE, and of course improves performance under dry conditions as compared with Comparative Example 2 that does not contain a conductive path material. In addition, no noticeable performance degradation was observed even under wet conditions, and it was confirmed that the power generation performance was improved by coexistence of low resistance and high diffusion.
  • Example PTFE Second fixing the amount of Example PTFE to 20% by mass ratio, the flake graphite (average particle size 15 [mu] m) at 80% of the balance between the acetylene black (particle diameter 40 nm, specific surface area 40 m 2 / GDL was obtained by similarly applying MPL inks with various ratios to g) to the carbon paper as a GDL substrate.
  • the electrical resistance in the thickness direction and the gas permeability (Gurley value) in the thickness direction of each GDL were measured by the same method as described above, and the influence of the acetylene black content on these properties is shown in FIG. .
  • the electrical resistance value (left side of the vertical axis) is indicated by a relative value of “1” when the acetylene black is “0” (corresponding to Comparative Example 2), and the Gurley value (right side of the vertical axis).
  • the relative value was set to “1” when the acetylene black was 80% (corresponding to Comparative Example 1) without containing scaly graphite.
  • the ratio of acetylene black is about 5%, the resistance value is considerably decreased, and as the ratio of acetylene black increases, the gas permeability decreases. From the viewpoint of gas permeability, the ratio of acetylene black is desirably 30% or less.
  • the electrical resistance in the thickness direction and the gas permeability (Gurley value) in the thickness direction of each GDL are measured by the same method as described above, and the influence of the artificial graphite content on these properties is shown in FIG. .
  • the reference value “1” in the figure is the same as in FIG.
  • the resistance value can be reduced by 30 compared with the case where carbon black or the like having a small particle size is used as the conductive path material. More blends of more than% are required. Moreover, since the particle size is large, it can be seen that the gas permeability does not deteriorate so much even if the mixing amount is increased.
  • MEA Membrane electrode assembly
  • GDL Gas diffusion layer
  • MPL Microporous layer
  • Scale-like graphite Conductive path material

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Abstract

Provided is a gas diffusion layer for a fuel cell, wherein it is possible to achieve both low resistance and high dispersibility in the gas diffusion layer, and to improve the performance of a solid polymer fuel cell. Also provided is a membrane electrode assembly for a solid polymer fuel cell equipped with such gas diffusion layer. A gas diffusion layer (30) is provided with a microporous layer (31) containing flake graphite and a conductive path material which has an average pore diameter smaller than that of the flake graphite, and which electrically connects the particles of the flake graphite with each other. A membrane electrode assembly (1) is formed by laminating the gas diffusion layer (30) on both surfaces of an electrolyte membrane (10) via a catalyst layer (20).

Description

燃料電池用ガス拡散層及びこれを用いた膜電極接合体Gas diffusion layer for fuel cell and membrane electrode assembly using the same
　本発明は、固体高分子形燃料電池（ＰＥＦＣ）に用いられるガス拡散層（ＧＤＬ：Ｇａｓ　Ｄｉｆｆｕｓｉｏｎ　Ｌａｙｅｒ）と、これを用いた膜電極接合体（ＭＥＡ：Ｍｅｍｂｒａｎｅ　Ｅｌｅｃｔｒｏｄｅ　Ａｓｓｅｍｂｌｙ）に関するものである。 The present invention relates to a gas diffusion layer (GDL: Gas Diffusion Layer) used in a polymer electrolyte fuel cell (PEFC) and a membrane electrode assembly (MEA: Membrane Electrode Assembly) using the same.
　プロトン伝導性固体高分子膜を用いた固体高分子形燃料電池は、他のタイプの燃料電池、例えば固体酸化物形燃料電池や溶融炭酸塩形燃料電池と比較して低温で作動することから、自動車などの移動体用動力源としても期待され、その実用も開始されている。 A polymer electrolyte fuel cell using a proton conductive solid polymer membrane operates at a lower temperature than other types of fuel cells, such as solid oxide fuel cells and molten carbonate fuel cells. It is also expected to be used as a power source for moving bodies such as automobiles, and its practical use has begun.
　固体高分子形燃料電池に使用されるガス拡散電極は、高分子電解質膜と同種あるいは異種のイオン交換樹脂（高分子電解質）で被覆された触媒担持カーボン微粒子を含有する電極触媒層と、この触媒層に反応ガスを供給すると共に触媒層に発生する電荷を集電するガス拡散層から成るものである。そして、このようなガス拡散電極の電極触媒層の側を高分子電解質膜に対向させた状態で接合することによって膜電極接合体が形成され、当該膜電極接合体の複数個をガス流路を備えたセパレータを介して積層することによって燃料電池が構成される。
　なお、ガス拡散層には、一般に、カーボン繊維を用いて作成されたカーボンペーパーや織布、不織布が用いられる。 A gas diffusion electrode used for a polymer electrolyte fuel cell includes an electrode catalyst layer containing catalyst-supported carbon fine particles coated with an ion exchange resin (polymer electrolyte) of the same type or different type from a polymer electrolyte membrane, and the catalyst. It comprises a gas diffusion layer for supplying a reaction gas to the layer and collecting charges generated in the catalyst layer. And the membrane electrode assembly is formed by joining the electrode catalyst layer side of such a gas diffusion electrode in a state of facing the polymer electrolyte membrane, and a plurality of the membrane electrode assemblies are connected to the gas flow path. A fuel cell is configured by stacking the separators provided.
The gas diffusion layer is generally made of carbon paper, woven fabric, or non-woven fabric made using carbon fibers.
　このような固体高分子形燃料電池に用いられるガス拡散層においては、当該ガス拡散層と触媒層との間の電気抵抗を下げると共に、ガスの流れを良くするための中間層として、ガス拡散層の触媒層側に、炭素材料などの導電性物質を主体とする微細多孔質層を備えたものが知られている。なお、このような微細多孔質層をガス拡散層の触媒層側に設けることによって、ガス拡散層を構成するカーボン繊維中にささくれがあったとしても、これが電解質膜を突き破るようなことを未然に防止することができ、当該微細多孔質層は電解質膜の保護層としても機能する。 In the gas diffusion layer used in such a polymer electrolyte fuel cell, the gas diffusion layer is used as an intermediate layer for reducing the electric resistance between the gas diffusion layer and the catalyst layer and improving the gas flow. A catalyst having a fine porous layer mainly composed of a conductive material such as a carbon material is known on the catalyst layer side. By providing such a fine porous layer on the catalyst layer side of the gas diffusion layer, even if there is a whirling in the carbon fiber that constitutes the gas diffusion layer, it is possible that this will break through the electrolyte membrane. The fine porous layer also functions as a protective layer for the electrolyte membrane.
　また、フラッディングや過剰乾きに対処するために、膜側における撥水性や排水性を調整することが可能な燃料電池用ガス拡散層として、活物質透過性と導電性を有する多孔質基材の表面に、薄片状導電物質と粉末状導電物質と撥水剤を含有し、活物質透過性と導電性を有する塗布層を備えたガス拡散層が提案されている。また、このようなガス拡散層の製造方法として、上記多孔質基材の表面に、薄片状導電物質と粉末状導電物質と撥水剤を含有する塗料組成物を塗布することが記載されている（特許文献１参照）。 Also, as a fuel cell gas diffusion layer that can adjust the water repellency and drainage on the membrane side in order to cope with flooding and excessive drying, the surface of a porous substrate having active material permeability and conductivity In addition, a gas diffusion layer has been proposed that includes a coating layer having a flaky conductive material, a powdered conductive material, and a water repellent and having active material permeability and conductivity. In addition, as a method for producing such a gas diffusion layer, it is described that a coating composition containing a flaky conductive material, a powdered conductive material, and a water repellent is applied to the surface of the porous substrate. (See Patent Document 1).
特開２００８－５９９１７号公報JP 2008-59917 A
　上記した微細多孔質膜や塗布層は、いずれもガス拡散層の一部を構成するものであり、ガス拡散層が全体としての導電性やガス拡散性が問われる以上、これら微細多孔質膜や塗布層についても、導電性と共にガス拡散性に優れていることが要求されることは言うまでもない。
　しかしながら、これら導電性とガス拡散性とは、一般にトレードオフ関係にあり、層の空孔率を増して拡散性を改善しようとすると電気抵抗が増大し、導電性を向上させるには、緻密な組織とすることが必要となって拡散性が悪化する結果となることから、これらを両立させることが極めて困難であるという問題があった。 The above-described fine porous film and coating layer constitute part of the gas diffusion layer, and as long as the gas diffusion layer is questioned about overall conductivity and gas diffusivity, these fine porous film and coating layer It goes without saying that the coating layer is required to have excellent gas diffusibility as well as conductivity.
However, these electrical conductivity and gas diffusivity are generally in a trade-off relationship. When an attempt is made to improve the diffusibility by increasing the porosity of the layer, the electrical resistance increases. There is a problem that it is extremely difficult to achieve both of these because it is necessary to form an organization and results in deterioration of diffusibility.
　本発明は、導電性物質を含む層を備えたガス拡散層を有する固体高分子形燃料電池における上記のような課題に着目してなされたものである。そして、その目的とするところは、通常、トレードオフ関係にあるガス拡散層の低抵抗と高拡散とを両立させることができ、固体高分子形燃料電池の性能向上に寄与するガス拡散層と、このようなガス拡散層を用いた膜電極接合体を提供することにある。 The present invention has been made by paying attention to the above problems in a polymer electrolyte fuel cell having a gas diffusion layer provided with a layer containing a conductive substance. The purpose of the gas diffusion layer, which can achieve both low resistance and high diffusion of the gas diffusion layer, which is usually in a trade-off relationship, contributes to the improvement of the performance of the polymer electrolyte fuel cell, An object of the present invention is to provide a membrane electrode assembly using such a gas diffusion layer.
　本発明者は、上記目的の達成に向けて、ガス拡散層を構成する材料の種類や、形状、サイズなどについて鋭意検討を繰り返した結果、鱗片状黒鉛と導電パス材を含んだ微細多孔質層を設けることによって、上記目的を達成することができることを見出し、本発明を完成するに到った。 As a result of intensive studies on the type, shape, size, etc. of the material constituting the gas diffusion layer, the inventor of the present invention has achieved a fine porous layer containing scaly graphite and a conductive path material. It has been found that the above object can be achieved by providing the present invention, and the present invention has been completed.
　すなわち、本発明は上記知見に基づくものであって、本発明の燃料電池用ガス拡散層は、固体高分子形燃料電池用膜電極接合体における触媒層に隣接して配置されるものであって、鱗片状黒鉛と、該鱗片状黒鉛を電気的に接続する導電パス材を含む微細多孔質層を備え、上記鱗片状黒鉛の平均粒径が導電パス材の平均粒径よりも大きいことを特徴としている。 That is, the present invention is based on the above knowledge, and the fuel cell gas diffusion layer of the present invention is disposed adjacent to the catalyst layer in the membrane electrode assembly for a polymer electrolyte fuel cell. A fine porous layer containing scaly graphite and a conductive path material electrically connecting the scaly graphite, wherein the average particle diameter of the scaly graphite is larger than the average particle diameter of the conductive path material. It is said.
　また、本発明の固体高分子形燃料電池用膜電極接合体は、本発明の上記ガス拡散層が電解質膜の両面に触媒層を介して積層されて成ることを特徴とする。
　そして、本発明の上記ガス拡散層を湿式法によって製造する場合には、撥水処理を施した多孔質基材に、１００／ｓのせん断速度における粘度が１０００～１００００ｍＰａ・ｓのインクを塗布することを特徴としている。 The membrane electrode assembly for a polymer electrolyte fuel cell of the present invention is characterized in that the gas diffusion layer of the present invention is laminated on both surfaces of an electrolyte membrane via a catalyst layer.
When the gas diffusion layer of the present invention is manufactured by a wet method, an ink having a viscosity of 1000 to 10,000 mPa · s at a shear rate of 100 / s is applied to a porous substrate that has been subjected to a water repellent treatment. It is characterized by that.
　本発明によれば、ガス拡散層における微細多孔質層を、鱗片状黒鉛と、平均粒径がこれよりも小さく、鱗片状黒鉛同士の電気的な接続に寄与する導電パス材を含むものとしたから、ガス拡散層における低抵抗と高拡散との両立が可能になる。 According to the present invention, the fine porous layer in the gas diffusion layer includes scaly graphite and a conductive path material having an average particle size smaller than this and contributing to electrical connection between scaly graphites. Therefore, it is possible to achieve both low resistance and high diffusion in the gas diffusion layer.
本発明の燃料電池用ガス拡散層を用いた膜電極接合体の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of the membrane electrode assembly using the gas diffusion layer for fuel cells of this invention. 本発明の燃料電池用ガス拡散層を用いた膜電極接合体の他の例を示す概略断面図である。It is a schematic sectional drawing which shows the other example of the membrane electrode assembly using the gas diffusion layer for fuel cells of this invention. 本発明の燃料電池用ガス拡散層の一部を構成する微細多孔質層の構造を模式的に示す拡大概略図（ａ）、この微細多孔質層を構成する鱗片状黒鉛の形状を示す平面図（ｂ）及び側面図（ｃ）である。FIG. 2 is an enlarged schematic view (a) schematically showing the structure of a fine porous layer constituting a part of the gas diffusion layer for a fuel cell of the present invention, and a plan view showing the shape of scaly graphite constituting the fine porous layer. It is (b) and a side view (c). 本発明の燃料電池用ガス拡散層を用いた膜電極接合体のさらに他の例を示す概略断面図である。It is a schematic sectional drawing which shows the further another example of the membrane electrode assembly using the gas diffusion layer for fuel cells of this invention. 本発明の燃料電池用ガス拡散層を用いた膜電極接合体の乾燥状態における発電性能を比較例と比較して示すグラフである。It is a graph which shows the electric power generation performance in the dry state of the membrane electrode assembly using the gas diffusion layer for fuel cells of this invention compared with a comparative example. 本発明の燃料電池用ガス拡散層を用いた膜電極接合体の湿潤状態における発電性能を比較例と比較して示すグラフである。It is a graph which shows the electric power generation performance in the wet state of the membrane electrode assembly using the gas diffusion layer for fuel cells of this invention compared with a comparative example. 本発明の燃料電池用ガス拡散層の電気抵抗及びガス透過性に及ぼす微細多孔質層中のアセチレンブラック含有量の影響を示すグラフである。It is a graph which shows the influence of acetylene black content in a microporous layer on the electrical resistance and gas permeability of the gas diffusion layer for fuel cells of this invention. 本発明の燃料電池用ガス拡散層の電気抵抗及びガス透過性に及ぼす微細多孔質層中の黒鉛含有量の影響を示すグラフである。It is a graph which shows the influence of the graphite content in a microporous layer on the electrical resistance and gas permeability of the gas diffusion layer for fuel cells of this invention.
　以下、本発明の燃料電池用ガス拡散層（ガス拡散層について、以下「ＧＤＬ」と略記する。）と、これを用いて成る膜電極接合体（以下、「ＭＥＡ」と略記する。）について、さらに詳細、かつ具体的に説明する。 Hereinafter, a fuel cell gas diffusion layer (hereinafter, abbreviated as “GDL”) and a membrane electrode assembly (hereinafter, abbreviated as “MEA”) using the same according to the present invention will be described. More detailed and specific description will be given.
　本発明の燃料電池用ＧＤＬは、上記したように、鱗片状黒鉛と導電パス材を含む微細多孔質層（以下、「ＭＰＬ（Ｍｉｃｒｏ　Ｐｏｒｏｕｓ　Ｌａｙｅｒ）」と略記する。）を備え、ＭＰＬ中の鱗片状黒鉛の平均粒径が導電パス材の平均粒径よりも大きいことを特徴としている。 As described above, the GDL for a fuel cell according to the present invention includes a fine porous layer (hereinafter abbreviated as “MPL (Micro Porous Layer)”) containing scaly graphite and a conductive path material, and the scale in the MPL. The average particle size of the graphite is larger than the average particle size of the conductive path material.
　通常、拡散性を向上するために、空孔径を大きくすべく鱗片状黒鉛を使用すると、黒鉛粒子間の接触面積が減少してＭＰＬの厚さ方向の電気抵抗が増加することになる。
　本発明のＧＤＬにおいては、上記鱗片状黒鉛に加えて、これよりも平均粒径の小さい導電パス材を混入してＭＰＬとしていることから、当該パス材を介して黒鉛粒子同士の接触面積が増加することになる。すなわち、鱗片状黒鉛を用いることによって空孔径を大きくし、高拡散とした場合でも、導電パス材の介在によって黒鉛粒子間の接触面積が増加し、電気抵抗が低下することから、このような材料から成るＭＰＬとすることによって、ガス拡散層における低抵抗と高拡散を両立させることができる。 In general, when scaly graphite is used to increase the pore diameter in order to improve the diffusibility, the contact area between the graphite particles decreases, and the electrical resistance in the thickness direction of the MPL increases.
In the GDL of the present invention, in addition to the scale-like graphite, a conductive path material having an average particle size smaller than this is mixed to form MPL, so that the contact area between the graphite particles increases through the path material. Will do. That is, even when the pore size is increased by using scaly graphite and the diffusion is high, the contact area between the graphite particles increases due to the presence of the conductive path material, and the electrical resistance decreases. By using the MPL made of, it is possible to achieve both low resistance and high diffusion in the gas diffusion layer.
　本発明の燃料電池用ＧＤＬを用いて成るＭＥＡとして、その構造例を図１に示す。
　図に示すＭＥＡ（１）は、電解質膜（１０）を中心とするアノード、カソード両極に、触媒層（２０）、ＭＰＬ（３１）、ＧＤＬ基材（３２）がそれぞれ配置されており、上記ＭＰＬ（３１）及びＧＤＬ基材（３２）によってＧＤＬ（３０）が構成されている。 An example of the structure of an MEA using the GDL for a fuel cell of the present invention is shown in FIG.
In the MEA (1) shown in the figure, the catalyst layer (20), the MPL (31), and the GDL base material (32) are respectively disposed on the anode and cathode both centered on the electrolyte membrane (10). GDL (30) is comprised by (31) and GDL base material (32).
　なお、上記図１では、ＧＤＬ（３０）がＧＤＬ基材（３２）とＭＰＬ（３１）とから成る場合を示したが、必ずしもＧＤＬ基材（３２）を用いる必要はなく、図２に示すように、ＭＰＬ（３１）のみから成るＧＤＬ（３０）を備えたＭＥＡ（１）とすることもでき、これによって、燃料電池の薄型・小型化が可能になる。 1 shows the case where the GDL (30) is composed of the GDL base material (32) and the MPL (31). However, it is not always necessary to use the GDL base material (32), as shown in FIG. In addition, the MEA (1) including the GDL (30) made only of the MPL (31) can be used, and this enables the fuel cell to be thinned and miniaturized.
　上記電解質膜（１０）としては、一般的に使用されているパーフルオロスルホン酸系電解質膜の他、炭化水素系電解質膜を使用することもできる。
　また、触媒層（２０）としては、白金又は白金合金をカーボン（オイルファーネスブラック、アセチレンブラック、サーマルブラック、チャンネルブラック、ケッチェンブラック等のカーボンブラック、黒鉛、活性炭等）に担持したものに、パーフルオロスルホン酸系電解質溶液や炭化水素系電解質溶液を混入して形成する。なお、必要に応じて、撥水剤や増孔剤を添加することも可能である。 As the electrolyte membrane (10), in addition to a perfluorosulfonic acid electrolyte membrane that is generally used, a hydrocarbon electrolyte membrane can also be used.
Further, as the catalyst layer (20), platinum or a platinum alloy supported on carbon (carbon black such as oil furnace black, acetylene black, thermal black, channel black, ketjen black, graphite, activated carbon, etc.) It is formed by mixing a fluorosulfonic acid electrolyte solution or a hydrocarbon electrolyte solution. In addition, it is also possible to add a water repellent and a pore increasing agent as needed.
　上記ＧＤＬ（３０）の一部をなすＭＰＬ（３１）は、図３（ａ）に示すように、鱗片状黒鉛（３５）と、導電パス材（３６）と、バインダ兼撥水剤としてのＰＴＦＥ（ポリテトラフルオロエチレン）等から成り、上記鱗片状黒鉛（３５）は、当該ＭＰＬ（３１）の面方向に沿った状態で存在することが多い。当該ＭＰＬ（３１）の厚さとしては、１０～１００μｍの範囲とすることが望ましい。 As shown in FIG. 3 (a), the MPL (31) forming a part of the GDL (30) is composed of scale-like graphite (35), a conductive path material (36), and PTFE as a binder and water repellent. Often composed of (polytetrafluoroethylene) or the like, the scaly graphite (35) often exists in a state along the surface direction of the MPL (31). The thickness of the MPL (31) is preferably in the range of 10 to 100 μm.
　ここで、導電パス材（３６）としては、例えば、オイルファーネスブラック、アセチレンブラック、サーマルブラック、チャンネルブラック等のカーボンブラック、黒鉛（天然黒鉛（燐片状、塊状、土状）、人造黒鉛、膨張黒鉛）、カーボン繊維等を用いることができる。これらの複数種を混合して使用することも可能である。
　なお、導電パス材として、カーボンブラック、黒鉛、カーボン繊維等の市販されている材料を用いることにより、コスト増を防止できる。また、カーボンブラックとして、アセチレンブラックを使用することにより、カーボン粒子の分散性がよくなり、生産性が向上する。導電パス材（３６）の平均粒径としては、１０ｎｍ～５μｍであることが好ましい。 Here, as the conductive path material (36), for example, carbon black such as oil furnace black, acetylene black, thermal black, channel black, graphite (natural graphite (flaky, massive, earthy)), artificial graphite, expanded Graphite), carbon fiber, and the like can be used. It is also possible to use a mixture of these plural types.
The use of a commercially available material such as carbon black, graphite, or carbon fiber as the conductive path material can prevent an increase in cost. Further, by using acetylene black as the carbon black, the dispersibility of the carbon particles is improved and the productivity is improved. The average particle diameter of the conductive path material (36) is preferably 10 nm to 5 μm.
　鱗片状黒鉛（３５）は、結晶性が高く、図２（ｂ）及び（ｃ）に示すように、アスペクト比（平面直径Ｄ／厚さＨ）が高いうろこ状の形状をなし、本発明において鱗片状黒鉛とは、厚さＨが０．０５～０．３μｍ、上記アスペクト比が３０～３００程度のものを意味する。
　当該鱗片状黒鉛（３５）の平均粒径（平面直径の平均）としては、５～５０μｍが好適である。５μｍよりも小さいと高拡散に寄与できず、５０μｍよりも大きくなると導電パス材の効果が小さくなる。 The flaky graphite (35) has a high crystallinity and has a scaly shape with a high aspect ratio (plane diameter D / thickness H) as shown in FIGS. 2 (b) and (c). The flaky graphite means one having a thickness H of 0.05 to 0.3 μm and an aspect ratio of about 30 to 300.
The average particle diameter (average of planar diameter) of the flake graphite (35) is preferably 5 to 50 μm. If it is smaller than 5 μm, it cannot contribute to high diffusion, and if it exceeds 50 μm, the effect of the conductive path material is reduced.
　上記鱗片状黒鉛（３５）と導電パス材（３６）の粒径比については、低抵抗の機能を導電パス材に、高拡散の機能を鱗片状黒鉛にそれぞれ持たせ、低抵抗と高分散の両立をより確実なものとする観点から、導電パス材の平均粒径を鱗片状黒鉛の０．０２～８０％とすることが望ましく、さらには０．１～３５％の範囲内とすることがより望ましい。 As for the particle size ratio between the scale-like graphite (35) and the conductive path material (36), the conductive path material has a low resistance function and the scale graphite has a high diffusion function. From the viewpoint of ensuring compatibility, it is desirable that the average particle diameter of the conductive path material is 0.02 to 80% of the scaly graphite, and more preferably within the range of 0.1 to 35%. More desirable.
　また、上記鱗片状黒鉛（３５）の平均粒径は、ＭＰＬ（３１）の厚さの５～５００％であることが望ましい。
　なお、ＭＰＬ（３１）の厚さは、上記したように１０～１００μｍ程度であるが、鱗片状黒鉛の平均粒径がＭＰＬ厚さの５％に満たない場合は、高拡散とすることができず、５００％を超えると、導電性が悪化する傾向があることから、これら特性の両立が難しくなる。 The average particle size of the scaly graphite (35) is preferably 5 to 500% of the thickness of the MPL (31).
The thickness of MPL (31) is about 10 to 100 μm as described above. However, when the average particle size of the flake graphite is less than 5% of the MPL thickness, high diffusion can be achieved. However, if it exceeds 500%, the conductivity tends to deteriorate, so that it is difficult to achieve both of these characteristics.
　導電パス材としてカーボンブラックを使用する場合の配合量については、低抵抗と高拡散をより確実に両立させる観点から、そのＭＰＬ中における含有量を５～３０％（質量比）とすることが望ましい。すなわち、カーボンブラックの含有量が５％よりも少ないと接触面積が稼げず、抵抗が下がらない一方、３０％よりも多くなると、小粒径が空孔を埋めてしまうため、拡散性が悪化する。
　また、カーボンブラックとして、その比表面積が１０００ｍ２／ｇ以上のものを使用することも望ましく、これによって抵抗をさらに低減することができる。 In the case of using carbon black as the conductive path material, the content in the MPL is preferably 5 to 30% (mass ratio) from the viewpoint of ensuring both low resistance and high diffusion more reliably. . That is, when the content of carbon black is less than 5%, the contact area cannot be obtained and the resistance does not decrease. On the other hand, when the content exceeds 30%, the small particle diameter fills the pores, so that the diffusibility deteriorates. .
It is also desirable to use carbon black having a specific surface area of 1000 m 2 / g or more, which can further reduce the resistance.
　導電パス材として、黒鉛を用いることにより、熱抵抗が低下し、低加湿性能が向上する。
　平均粒径が３μｍ以上の黒鉛を用いる場合、これが導電パス材として機能するためには、粒径の小さなカーボンブラック等に比べると、より多くの黒鉛を配合する必要があり、ＭＰＬ中の含有量として３０％（質量比）以上が必要となる。 By using graphite as the conductive path material, the thermal resistance is lowered and the low humidification performance is improved.
When graphite having an average particle size of 3 μm or more is used, in order for this to function as a conductive path material, it is necessary to add more graphite compared to carbon black or the like having a small particle size, and the content in MPL 30% (mass ratio) or more is required.
　なお、平均粒径が３μｍ以上の黒鉛では、粒径が大きく、混入量を増やしてたとしても拡散性はあまり悪化しないため、鱗片状黒鉛が混在し、バインダーとしての必要量が含まれている限り、導電パス材としての黒鉛含有量には、特に上限はない。
　ただし、粒径がさらに小さい黒鉛を用いる場合には、カーボンブラックと同様の少ない配合比でも抵抗が低下し、拡散性を確保する観点から、上限値を５０％程度に設定する必要がある。 In addition, graphite having an average particle size of 3 μm or more has a large particle size, and even if the mixing amount is increased, the diffusivity does not deteriorate so much, so flake graphite is mixed and the necessary amount as a binder is included. As long as there is no particular upper limit to the graphite content as the conductive path material.
However, when graphite having a smaller particle size is used, the resistance decreases even with a small blending ratio similar to that of carbon black, and the upper limit value needs to be set to about 50% from the viewpoint of ensuring diffusibility.
　図１に示したように、ＭＰＬ（３１）をＧＤＬ基材（３２）と接合して使用する場合、ＧＤＬ基材としては、カーボンペーパー、カーボンクロス、不織布等の炭素繊維で形成された材料に、撥水剤としてＰＴＦＥ等を含浸したものが用いられる。
　なお、当該ＧＤＬを適用するＭＥＡの排水特性やセパレータの表面性状によっては、基材の撥水処理を行わないことや、親水処理を行う場合もある。また、上記ＧＤＬ基材にも、黒鉛、カーボンブラック、あるいはこれらの混合物を含浸してもよい。 As shown in FIG. 1, when MPL (31) is used while being joined to a GDL substrate (32), the GDL substrate is made of a material formed of carbon fibers such as carbon paper, carbon cloth, and nonwoven fabric. A water repellent impregnated with PTFE or the like is used.
Depending on the drainage characteristics of the MEA to which the GDL is applied and the surface properties of the separator, the substrate may not be subjected to water repellent treatment or may be subjected to hydrophilic treatment. Further, the GDL substrate may be impregnated with graphite, carbon black, or a mixture thereof.
　なお、本発明の上記燃料電池用ガス拡散層を湿式法によって製造する場合には、上記したような撥水処理を施した多孔質基材に、１００／ｓのせん断速度における粘度が１０００～１００００ｍＰａ・ｓのインクを塗布するようになすことが好ましい。
　すなわち、上記粘度が１０００ｍＰａ・ｓより小さいと、カーボンペーパーなどから成る多孔質基材中へのインクの入り込みが増加し、ガス拡散層のガス透過性が低下する傾向がある。一方、１００００ｍＰａ・ｓより大きくなると、インクの基材中への入り込みは少なくなるものの、インクを均一な厚さに塗布することが困難となり、表面に塊や気泡が生じやすくなることがある。なお、インクの粘度を調整するには、例えばポリアクリル酸系やポリエーテル系などの増粘剤の添加量を増減することによって行うことができる。 When the gas diffusion layer for a fuel cell of the present invention is produced by a wet method, the viscosity at a shear rate of 100 / s is 1000 to 10000 mPas on the porous substrate subjected to the water repellent treatment as described above. It is preferable to apply s ink.
That is, when the viscosity is less than 1000 mPa · s, the ink penetration into the porous substrate made of carbon paper or the like increases, and the gas permeability of the gas diffusion layer tends to decrease. On the other hand, when it exceeds 10,000 mPa · s, although the ink does not enter the base material, it becomes difficult to apply the ink to a uniform thickness, and lump or bubbles may be easily generated on the surface. The viscosity of the ink can be adjusted, for example, by increasing or decreasing the amount of thickening agent such as polyacrylic acid or polyether.
　本発明の固体高分子形燃料電池用膜電極接合体（ＭＥＡ）は、上記ＧＤＬ（３０）が電解質膜（１０）の両面に触媒層（２０）を介して積層されたものであり、上記ＧＤＬ（３０）が導電性と拡散性とが両立できていることから、高い発電性能を発揮することができる。
　このＭＥＡの作製方法としては、電解質膜（１０）に触媒層（２０）をホットプレスで転写又は直接塗布したものに、ＧＤＬ（３０）を接合する場合と、ＧＤＬ（ＭＰＬとＧＤＬ基材から成る場合には、そのＭＰＬ側）に触媒層（２０）を予め塗布したものを電解質膜（１）にホットプレスで接合する場合があるが、そのどちらでも構わない。 A membrane electrode assembly (MEA) for a polymer electrolyte fuel cell according to the present invention is obtained by laminating the GDL (30) on both surfaces of the electrolyte membrane (10) via a catalyst layer (20). Since (30) is compatible with conductivity and diffusivity, high power generation performance can be exhibited.
As a method for producing this MEA, the GDL (30) is bonded to the electrolyte membrane (10) which is transferred or directly coated with the catalyst layer (20) by hot pressing, and the GDL (consisting of MPL and GDL base material). In some cases, the catalyst layer (20) previously applied to the MPL side) may be joined to the electrolyte membrane (1) by hot pressing, either of which may be used.
　本発明の固体高分子形燃料電池用ＭＥＡにおいては、アノード側の鱗片状黒鉛の平均粒径をカソード側のそれの平均粒径よりも小さくすることが望ましく、これによってアノードの拡散性が低下し、カソードの拡散性が向上するため、低加湿性能、高加湿性能共に向上することになる。 In the MEA for a polymer electrolyte fuel cell of the present invention, it is desirable to make the average particle size of the flaky graphite on the anode side smaller than that on the cathode side, thereby reducing the diffusibility of the anode. Since the diffusibility of the cathode is improved, both the low humidification performance and the high humidification performance are improved.
　また、比表面積が１０００ｍ２／ｇ以上のカーボンブラックを導電パス材として使用する場合、これを少なくともアノード側に使用することが望ましい。すなわち、このようなカーボンブラックは、水蒸気吸着性が向上するため、これをアノードに使用することによって、低加湿性能を向上させることができる。 Further, when carbon black having a specific surface area of 1000 m 2 / g or more is used as the conductive path material, it is desirable to use it at least on the anode side. That is, since such carbon black has improved water vapor adsorption, low humidification performance can be improved by using it for the anode.
　また、比表面積が１０００ｍ２／ｇ以上のカーボンブラックを導電パス材として使用する場合、このようなカーボンブラックをカソード側よりもアノード側に多く含有させることが望ましい。
　これによって、アノードの水蒸気吸着性をカソードよりも向上させることができ、カソードからアノードへの水の逆拡散が増加し、低加湿性能、高加湿性能共に向上することになる。 In addition, when carbon black having a specific surface area of 1000 m 2 / g or more is used as the conductive path material, it is desirable to contain more carbon black on the anode side than on the cathode side.
As a result, the water vapor adsorptivity of the anode can be improved as compared with the cathode, the back diffusion of water from the cathode to the anode is increased, and both the low humidification performance and the high humidification performance are improved.
　さらに、本発明のＭＥＡにおいては、比表面積が１０００ｍ２／ｇ以上の上記カーボンブラックをカソード面内の乾燥側に多く、湿潤側に少なくなるように含有させることによって、低加湿性能、高加湿性能共に向上させることができる。
　このとき、カソード面内の乾燥側、湿潤側については、カソードガスと冷却水の流れ方向が対向流の場合、カソード入口が乾燥側、カソード出口が湿潤側となる。一方、カソードガスと冷却水の流れが並行流の場合には、カソード入口が湿潤側、カソード出口が乾燥側となる。 Furthermore, in the MEA of the present invention, the above-mentioned carbon black having a specific surface area of 1000 m 2 / g or more is contained on the cathode side in such a way that it is more on the dry side and less on the wet side, thereby reducing the humidification performance and the high humidification performance. Both can be improved.
At this time, regarding the dry side and the wet side in the cathode surface, when the flow direction of the cathode gas and the cooling water is a counter flow, the cathode inlet is the dry side and the cathode outlet is the wet side. On the other hand, when the cathode gas and the cooling water flow are parallel flows, the cathode inlet is on the wet side and the cathode outlet is on the dry side.
　なお、本発明のＭＥＡにおいては、図１に示したようなガス拡散層（３０）のＭＰＬ（３１）を触媒層（２０）の側に配置したものに限定されず、図４に示すように、ガス拡散層（３０）のＭＰＬ（３１）を触媒層（２０）側に加え、セパレータ側、すなわち電解質膜の反対側に配置することも可能である。 In the MEA of the present invention, the MPL (31) of the gas diffusion layer (30) as shown in FIG. 1 is not limited to the arrangement on the catalyst layer (20) side, but as shown in FIG. It is also possible to add the MPL (31) of the gas diffusion layer (30) to the catalyst layer (20) side and arrange it on the separator side, that is, on the opposite side of the electrolyte membrane.
　以下、本発明を実施例に基づいて具体的に説明するが、本発明は、これらの実施例のみに限定されないことは言うまでもない。 Hereinafter, although the present invention will be specifically described based on examples, it is needless to say that the present invention is not limited only to these examples.
〔１〕第１実施例
（発明例１）
　ＧＤＬ基材として、ＰＴＦＥにより質量比で１０％の撥水処理した厚さ１５０μｍのカーボンペーパーを用いた。この上に、厚さ０．１μｍ、平均粒径Ｄ５０が１５μｍの燐片状黒鉛、平均粒径が４０ｎｍ、比表面積が４０ｍ２／ｇのアセチレンブラック、ＰＴＦＥを６：２：２の割合（質量比）で含み、せん断速度１００／ｓの時の粘度が３５００ｍＰａ・ｓであるＭＰＬインクを塗布し、当該発明例のＧＤＬを得た。なお、ＭＰＬ目付けは２３ｇ／ｍ２、ＭＰＬ厚さは２０μｍであった。 [1] First Embodiment (Invention Example 1)
As the GDL base material, carbon paper having a thickness of 150 μm treated with water repellent with a mass ratio of 10% by PTFE was used. On top of this, flake graphite having a thickness of 0.1 μm and an average particle diameter D50 of 15 μm, acetylene black having an average particle diameter of 40 nm and a specific surface area of 40 m 2 / g, PTFE in a ratio of 6: 2: 2 (mass The MPL ink having a viscosity of 3500 mPa · s at a shear rate of 100 / s was applied to obtain the GDL of the invention example. The MPL basis weight was 23 g / m 2 and the MPL thickness was 20 μm.
（発明例２）
　ＧＤＬ基材として、ＰＴＦＥにより質量比で１０％の撥水処理した厚さ１５０μｍのカーボンペーパーを用いた。そして、この上に、厚さ０．１μｍ、平均粒径Ｄ５０が１５μｍの燐片状黒鉛、平均粒径が２０ｎｍ、比表面積が１４００ｍ２／ｇのカーボンブラック（ケッチェンブラック）、ＰＴＦＥを７：１：２の割合（質量比）で含み、同様のせん断速度における粘度が３０００ｍＰａ・ｓであるむＭＰＬインクを塗布し、当該発明例２のＧＤＬを得た。 (Invention Example 2)
As the GDL base material, carbon paper having a thickness of 150 μm treated with water repellent with a mass ratio of 10% by PTFE was used. On top of this, flake graphite having a thickness of 0.1 μm and an average particle diameter D50 of 15 μm, carbon black (Ketjen black) having an average particle diameter of 20 nm and a specific surface area of 1400 m 2 / g, PTFE 7: An MPL ink containing a 1: 2 ratio (mass ratio) and having a viscosity of 3000 mPa · s at the same shear rate was applied to obtain the GDL of Invention Example 2.
（発明例３）
　上記燐片状黒鉛、平均粒径Ｄ５０が５μｍの人造黒鉛、ＰＴＦＥを５：３：２の割合（質量比）で含み、上記粘度が２５００ｍＰａ・ｓのＭＰＬインクを塗布したこと以外は、上記発明例１と同様の操作を繰り返すことによって、当該発明例３のＧＤＬを得た。 (Invention Example 3)
The invention described above except that the flake graphite, artificial graphite having an average particle diameter D50 of 5 μm, PTFE is contained at a ratio (mass ratio) of 5: 3: 2, and the MPL ink having the viscosity of 2500 mPa · s is applied. By repeating the same operation as in Example 1, the GDL of Invention Example 3 was obtained.
（発明例４）
　上記燐片状黒鉛を平均粒径Ｄ５０が６μｍのものに替え、上記粘度が４０００ｍＰａ・ｓであるＭＰＬインクを塗布したこと以外は、上記発明例１と同様の操作を繰り返すことによって、当該発明例４のＧＤＬを得た。なお、ＭＰＬ目付けは３０ｇ／ｍ２、ＭＰＬ厚さは２０μｍであった。 (Invention Example 4)
By replacing the flake graphite with one having an average particle diameter D50 of 6 μm and applying MPL ink having a viscosity of 4000 mPa · s, the same operation as in Invention Example 1 was repeated, thereby repeating the invention example. 4 GDLs were obtained. The MPL basis weight was 30 g / m 2 and the MPL thickness was 20 μm.
（発明例５）
　燐片状黒鉛、アセチレンブラック、ＰＴＦＥを７：１：２の割合（質量比）で含み、上記粘度が３０００ｍＰａ・ｓであるＭＰＬインクを塗布したこと以外は、上記発明例１と同様の操作を繰り返すことによって、当該発明例５のＧＤＬを得た。 (Invention Example 5)
Except that flake graphite, acetylene black and PTFE were included at a ratio (mass ratio) of 7: 1: 2, and the MPL ink having the viscosity of 3000 mPa · s was applied, the same operation as in Invention Example 1 was performed. By repeating, the GDL of the invention example 5 was obtained.
（発明例６）
　燐片状黒鉛、アセチレンブラック、ＰＴＦＥを７．５：０．５：２の割合（質量比）で含み、上記粘度が３０００ｍＰａ・ｓであるＭＰＬインクを塗布したこと以外は、上記発明例１と同様の操作を繰り返すことによって、当該発明例６のＧＤＬを得た。 (Invention Example 6)
Except for applying flake graphite, acetylene black, PTFE in a ratio (mass ratio) of 7.5: 0.5: 2, and applying the MPL ink having the viscosity of 3000 mPa · s, By repeating the same operation, the GDL of Invention Example 6 was obtained.
（比較例１）
　鱗片状黒鉛を配合することなく、上記アセチレンブラックとＰＴＦＥを８：２の割合（質量比）で含むと共に、上記粘度が２０００ｍＰａ・ｓであるＭＰＬインクを塗布したこと以外は、上記発明例１と同様の操作を繰り返すことによって、当該比較例１のＧＤＬを得た。なお、ＭＰＬ目付けは２７ｇ／ｍ２、ＭＰＬ厚さは２０μｍであった。 (Comparative Example 1)
Example 1 except that MPL ink containing acetylene black and PTFE at a ratio (mass ratio) of 8: 2 and having a viscosity of 2000 mPa · s was applied without blending scale-like graphite. By repeating the same operation, the GDL of Comparative Example 1 was obtained. The MPL basis weight was 27 g / m 2 and the MPL thickness was 20 μm.
（比較例２）
　導電パス材として機能する材料を配合することなく、上記鱗片状黒鉛とＰＴＦＥを８：２の割合（質量比）で含み、上記粘度が２０００ｍＰａ・ｓであるＭＰＬインクを塗布したこと以外は、上記発明例１と同様の操作を繰り返すことによって、当該比較例２のＧＤＬを得た。なお、ＭＰＬ目付けは２０ｇ／ｍ２、ＭＰＬ厚さは２０μｍであった。 (Comparative Example 2)
Other than having applied the MPL ink which contains the said scaly graphite and PTFE in the ratio (mass ratio) of 8: 2, and the said viscosity is 2000 mPa * s, without mix | blending the material which functions as a conductive path material. By repeating the same operation as in Invention Example 1, the GDL of Comparative Example 2 was obtained. The MPL basis weight was 20 g / m 2 and the MPL thickness was 20 μm.
　また、上記実施例においては、ＭＰＬインクのＧＤＬ基材への過剰な浸透を防止して、ＧＤＬのガス透過性を確保するために、せん断速度１００／ｓにおける粘度が２０００～４０００ｍＰａ・ｓのインクを用いると共に、ＧＤＬ基材に予め撥水処理を施すようにしている。
　これに対し、ＧＤＬ基材に、撥水処理を施すことなく、上記実施例１のＭＰＬインクを塗布した場合には、インクの浸透深さが撥水処理を行った場合に較べて約２倍に増加することが確認されている。 Further, in the above embodiment, in order to prevent excessive penetration of the MPL ink into the GDL substrate and to secure the gas permeability of GDL, the ink having a viscosity of 2000 to 4000 mPa · s at a shear rate of 100 / s is used. In addition, the water repellent treatment is applied to the GDL base material in advance.
On the other hand, when the MPL ink of Example 1 was applied to the GDL substrate without performing the water repellent treatment, the ink penetration depth was about twice that of the case where the water repellent treatment was performed. Has been confirmed to increase.
（ＧＤＬ単体電気抵抗の測定）
　上記各発明例及び比較例により得られたＧＤＬの厚さ方向の電気抵抗の測定結果を表１に示す。
　測定に当たっては、面積０．９５ｃｍ２のＧＤＬの両面を金箔で挟み、荷重をかけた状態で通電して測定した。電流値は１Ａで、５ＭＰａまでを１サイクルとし、２サイクル目の１ＭＰａにおける値を比較した。なお、表１における電気抵抗値については、比較例２（導電パス材なし）の測定値を「１」とする相対値で示した。 (Measurement of GDL single unit electrical resistance)
Table 1 shows the measurement results of the electrical resistance in the thickness direction of the GDLs obtained by the above invention examples and comparative examples.
In the measurement, both sides of GDL having an area of 0.95 cm 2 were sandwiched between gold foils, and measurement was performed by applying current in a state where a load was applied. The current value was 1 A, up to 5 MPa was taken as one cycle, and the value at 1 MPa in the second cycle was compared. In addition, about the electrical resistance value in Table 1, it showed with the relative value which set the measured value of the comparative example 2 (no conductive path material) to "1".
（ガス透過性の測定）
　上記各発明例及び比較例により得られたＧＤＬの厚さ方向のガス透過性として、ガーレー試験機法により１００ｍｌのガスが透過するのに要する時間（ガーレー値）を測定し、比較した。その結果を表１に併せて示す。なお、表１においては、比較例１（鱗片状黒鉛なし）の測定値を「１」とする相対値で示した。 (Measurement of gas permeability)
As the gas permeability in the thickness direction of the GDL obtained by each of the above inventive examples and comparative examples, the time (Gurley value) required for 100 ml of gas to permeate was measured and compared by the Gurley tester method. The results are also shown in Table 1. In Table 1, the measured value of Comparative Example 1 (no flaky graphite) is shown as a relative value with “1”.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　導電パス材を含まない比較例２に対して、鱗片状黒鉛に加えて導電パス材を含む発明例の抵抗値が低く、特に、比表面積が１０００ｍ２／ｇ以上のカーボンブラックを使用している実施例２のＧＤＬにおいては、比表面積が４０ｍ２／ｇのアセチレンブラックを使用している実施例１よりも低い抵抗値が確認された。
　また、ガス透過性については、導電パス材を含まない比較例２に対して、鱗片状黒鉛に加えて導電パス材を含む発明例のガス透過性は低くなる（ガーレー値は高くなる）が、鱗片状黒鉛を含まない比較例１に比べると、十分にガス透過性は高い（ガーレー値は低い）。又、比表面積が１０００ｍ２／ｇ以上のカーボンブラックを使用している発明例２のＧＤＬにおいては、アセチレンブラックよりも分散性が悪化することも影響し、少ない含有量でも発明例１よりガス透過性は低くなる（ガーレー値は高くなる）が、燐片状黒鉛を含まない比較例１に比べると、十分にガス透過性は高い（ガーレー値は低い）。 Compared to Comparative Example 2 that does not include a conductive path material, the resistance value of the invention example including the conductive path material in addition to the flaky graphite is low, and in particular, carbon black having a specific surface area of 1000 m 2 / g or more is used. In the GDL of Example 2, a resistance value lower than that of Example 1 in which acetylene black having a specific surface area of 40 m 2 / g was used was confirmed.
As for gas permeability, the gas permeability of the invention example including the conductive path material in addition to the flaky graphite is lower than the comparative example 2 not including the conductive path material (the Gurley value is increased), The gas permeability is sufficiently high (the Gurley value is low) compared to Comparative Example 1 that does not contain scale-like graphite. In addition, GDL of Invention Example 2 using carbon black having a specific surface area of 1000 m 2 / g or more is affected by deterioration of dispersibility as compared with acetylene black, and gas permeation from Invention Example 1 even with a small content. However, the gas permeability is sufficiently high (the Gurley value is low) as compared with Comparative Example 1 that does not contain flake graphite.
（セル発電性能の評価）
　まず、上記発明例１と、比較例１及び２により得られたＧＤＬを用いたＭＥＡを作製した。
　すなわち、パーフルオロスルホン酸系電解質から成る電解質膜の両面に、白金担持カーボンと上記電解質膜と同様のパーフルオロスルホン酸系電解質から成る触媒層を塗布した状態の接合体を上記ＧＤＬでそれぞれ挟み込み、ＭＥＡ（アクティブエリア：５×２ｃｍ）を得た。 (Evaluation of cell power generation performance)
First, an MEA using the GDL obtained in Invention Example 1 and Comparative Examples 1 and 2 was prepared.
That is, the GDL is sandwiched by the GDL with a platinum-supported carbon and a catalyst layer made of the same perfluorosulfonic acid electrolyte as the electrolyte membrane on both sides of the electrolyte membrane made of the perfluorosulfonic acid electrolyte, MEA (active area: 5 × 2 cm) was obtained.
　次に、上記により得られたＭＥＡから成る小型単セルを用いて、Ｈ２／Ａｉｒ、８０℃、２００ｋＰａ＿ａの条件で発電評価を行なった。
　そして、アノード及びカソードの相対湿度がそれぞれ、３０％ＲＨ、２０％ＲＨの場合（乾燥条件）における２Ａ／ｃｍ２での発電評価結果を図５に、アノード及びカソードの相対湿度が共に９０％ＲＨの場合（湿潤条件）における２Ａ／ｃｍ２での発電評価結果を図６に示す。なお、図中におけるセル電圧（縦軸）は、鱗片状黒鉛を含まない比較例１のＧＤＬを用いたＭＥＡの値を「１」とした場合の相対値で示した。 Next, power generation evaluation was performed under the conditions of H 2 / Air, 80 ° C., and 200 kPa_a using the small unit cell made of MEA obtained as described above.
FIG. 5 shows the results of power generation evaluation at 2 A / cm 2 when the relative humidity of the anode and cathode is 30% RH and 20% RH (drying conditions), respectively, and the relative humidity of the anode and cathode is 90% RH. FIG. 6 shows the results of power generation evaluation at 2 A / cm 2 in the case of (wet conditions). In addition, the cell voltage (vertical axis) in the figure is shown as a relative value when the value of MEA using GDL of Comparative Example 1 not containing scale-like graphite is “1”.
　本発明による発明例１のＧＤＬを用いたＭＥＡにおいては、上記比較例１によるものに比べ、乾燥条件にて約９％、湿潤条件においては約１５％の性能向上が確認された。
　なお、発明例１のＧＤＬでは、粒径の小さなアセチレンブラックを含むものの、鱗片状黒鉛とＰＴＦＥのみを含み、導電パス材を含まない比較例２と比べても、乾燥条件での性能向上はもちろんのこと、湿潤条件でも目立った性能低下は確認されておらず、低抵抗と高拡散の両立により、発電性能が向上していることが確認された。 In the MEA using GDL of Invention Example 1 according to the present invention, a performance improvement of about 9% under dry conditions and about 15% under wet conditions was confirmed as compared with that according to Comparative Example 1 above.
The GDL of Invention Example 1 contains acetylene black having a small particle diameter, but only contains scaly graphite and PTFE, and of course improves performance under dry conditions as compared with Comparative Example 2 that does not contain a conductive path material. In addition, no noticeable performance degradation was observed even under wet conditions, and it was confirmed that the power generation performance was improved by coexistence of low resistance and high diffusion.
〔２〕第２実施例
　ＰＴＦＥの配合量を質量比で２０％に固定し、残部の８０％における上記鱗片状黒鉛（平均粒径１５μｍ）と上記アセチレンブラック（粒径４０ｎｍ、比表面積４０ｍ２／ｇ）との割合を種々変更したＭＰＬインクをＧＤＬ基材としての上記カーボンペーパーにそれぞれ同様に塗布することによってＧＤＬを得た。 [2] Second fixing the amount of Example PTFE to 20% by mass ratio, the flake graphite (average particle size 15 [mu] m) at 80% of the balance between the acetylene black (particle diameter 40 nm, specific surface area 40 m 2 / GDL was obtained by similarly applying MPL inks with various ratios to g) to the carbon paper as a GDL substrate.
　そして、上記同様の方法によって、各ＧＤＬの厚さ方向の電気抵抗と、厚さ方向のガス透過性（ガーレー値）とを測定し、これら特性に及ぼすアセチレンブラック含有量の影響を図７に示す。
　なお、図において、電気抵抗値（縦軸左側）については、アセチレンブラックが「０」の場合（比較例２に相当）を「１」とする相対値で示すと共に、ガーレー値（縦軸右側）については、鱗片状黒鉛を含むことなく、アセチレンブラックが８０％の場合（比較例１に相当）を「１」とする相対値で示した。 Then, the electrical resistance in the thickness direction and the gas permeability (Gurley value) in the thickness direction of each GDL were measured by the same method as described above, and the influence of the acetylene black content on these properties is shown in FIG. .
In the figure, the electrical resistance value (left side of the vertical axis) is indicated by a relative value of “1” when the acetylene black is “0” (corresponding to Comparative Example 2), and the Gurley value (right side of the vertical axis). For, the relative value was set to “1” when the acetylene black was 80% (corresponding to Comparative Example 1) without containing scaly graphite.
　図７に示す結果から、アセチレンブラックの割合が５％程度となることによって、抵抗値がかなり低下することと共に、アセチレンブラックの割合が増加するにつれ、ガス透過性が低下していることが分かり、ガス透過性の観点から、アセチレンブラックの割合は、３０％以下であることが望ましい。 From the results shown in FIG. 7, it can be seen that when the ratio of acetylene black is about 5%, the resistance value is considerably decreased, and as the ratio of acetylene black increases, the gas permeability decreases. From the viewpoint of gas permeability, the ratio of acetylene black is desirably 30% or less.
〔３〕第３実施例
　ＰＴＦＥの配合量を質量比で２０％に固定し、残部の８０％における上記鱗片状黒鉛（平均粒径１５μｍ）と上記人造黒鉛（平均粒径５μｍ）との割合を種々変更したＭＰＬインクをＧＤＬ基材としての上記カーボンペーパーにそれぞれ同様に塗布することによってＧＤＬを得た。 [3] Third Example The amount of PTFE was fixed at 20% by mass ratio, and the ratio of the scale-like graphite (average particle size 15 μm) to the artificial graphite (average particle size 5 μm) in the remaining 80% was determined as follows. GDL was obtained by applying variously modified MPL inks to the carbon paper as a GDL substrate in the same manner.
　そして、上記同様の方法によって、各ＧＤＬの厚さ方向の電気抵抗と、厚さ方向のガス透過性（ガーレー値）とを測定し、これら特性に及ぼす人造黒鉛含有量の影響を図８に示す。
　なお、図における基準値「１」については、図７と変わらない。 Then, the electrical resistance in the thickness direction and the gas permeability (Gurley value) in the thickness direction of each GDL are measured by the same method as described above, and the influence of the artificial graphite content on these properties is shown in FIG. .
The reference value “1” in the figure is the same as in FIG.
　図８に示す結果から、平均粒径が比較的大きな人造黒鉛を用いる場合には、抵抗値を低減するには、導電パス材として粒径の小さなカーボンブラック等を使用した場合に較べて、３０％以上というより多くの配合が必要となる。また、粒径が大きいことから、混入量を増やしても、ガス透過性はあまり悪化しないことが判る。 From the results shown in FIG. 8, when artificial graphite having a relatively large average particle size is used, the resistance value can be reduced by 30 compared with the case where carbon black or the like having a small particle size is used as the conductive path material. More blends of more than% are required. Moreover, since the particle size is large, it can be seen that the gas permeability does not deteriorate so much even if the mixing amount is increased.
　１　膜電極接合体（ＭＥＡ）
１０　電解質膜
２０　触媒層　
３０　ガス拡散層（ＧＤＬ）
３１　微細多孔質層（ＭＰＬ）
３５　鱗片状黒鉛
３６　導電パス材 1 Membrane electrode assembly (MEA)
10 Electrolyte membrane 20 Catalyst layer
30 Gas diffusion layer (GDL)
31 Microporous layer (MPL)
35 Scale-like graphite 36 Conductive path material

Claims (10)

  1. 　固体高分子形燃料電池用膜電極接合体の触媒層に隣接するガス拡散層であって、鱗片状黒鉛と、該鱗片状黒鉛を電気的に接続する導電パス材を含む微細多孔質層を備え、上記鱗片状黒鉛の平均粒径が導電パス材の平均粒径よりも大きいことを特徴とする燃料電池用ガス拡散層。 A gas diffusion layer adjacent to a catalyst layer of a membrane electrode assembly for a polymer electrolyte fuel cell, comprising a fine porous layer containing scaly graphite and a conductive path material electrically connecting the scaly graphite A gas diffusion layer for fuel cells, wherein the average particle size of the flake graphite is larger than the average particle size of the conductive path material.
  2. 　上記導電パス材の平均粒径が鱗片状黒鉛の平均粒径の０．０２～８０％であることを特徴とする請求項１に記載の燃料電池用ガス拡散層。 The gas diffusion layer for a fuel cell according to claim 1, wherein the average particle diameter of the conductive path material is 0.02 to 80% of the average particle diameter of the flaky graphite.
  3. 　上記鱗片状黒鉛の平均粒径が上記微細多孔質層の厚さの５～５００％であることを特徴とする請求項１又は２に記載の燃料電池用ガス拡散層。 3. The fuel cell gas diffusion layer according to claim 1 or 2, wherein the scale-like graphite has an average particle diameter of 5 to 500% of the thickness of the fine porous layer.
  4. 　上記導電パス材がカーボンブラック、黒鉛及びカーボン繊維から成る群から選ばれた少なくとも１種であることを特徴とする請求項１～３のいずれか１つの項に記載の燃料電池用ガス拡散層。 The gas diffusion layer for a fuel cell according to any one of claims 1 to 3, wherein the conductive path material is at least one selected from the group consisting of carbon black, graphite, and carbon fibers.
  5. 　上記導電パス材が粒径３μｍ以上の黒鉛であって、上記微細多孔質層中の含有量が質量比で３０％以上であることを特徴とする請求項４に記載の燃料電池用ガス拡散層。 The gas diffusion layer for a fuel cell according to claim 4, wherein the conductive path material is graphite having a particle size of 3 µm or more, and the content in the fine porous layer is 30% or more by mass ratio. .
  6. 　上記導電パス材がカーボンブラックであって、上記微細多孔質層中の含有量が質量比で５～３０％であることを特徴とする請求項４に記載の燃料電池用ガス拡散層。 The gas diffusion layer for a fuel cell according to claim 4, wherein the conductive path material is carbon black, and the content in the fine porous layer is 5 to 30% by mass ratio.
  7. 　上記カーボンブラックがアセチレンブラックであることを特徴とする請求項６に記載の燃料電池用ガス拡散層。 The gas diffusion layer for a fuel cell according to claim 6, wherein the carbon black is acetylene black.
  8. 　上記カーボンブラックの比表面積が１０００ｍ２／ｇ以上であることを特徴とする請求項６に記載の燃料電池用ガス拡散層。 The gas diffusion layer for a fuel cell according to claim 6, wherein the specific surface area of the carbon black is 1000 m 2 / g or more.
  9. 　請求項１～８のいずれか１つの項に記載のガス拡散層が電解質膜の両面に触媒層を介して積層されて成ることを特徴とする固体高分子形燃料電池用膜電極接合体。 9. A membrane / electrode assembly for a polymer electrolyte fuel cell, wherein the gas diffusion layer according to any one of claims 1 to 8 is laminated on both surfaces of an electrolyte membrane via a catalyst layer.
  10. 　 請求項１～８のいずれか１つの項に記載のガス拡散層を湿式法により製造するに際し、撥水処理を施した多孔質基材に、１００／ｓのせん断速度における粘度が１０００～１００００ｍＰａ・ｓのインクを塗布することを特徴とする燃料電池用ガス拡散層の製造方法。 When the gas diffusion layer according to any one of claims 1 to 8 is produced by a wet method, the water repellent porous substrate has a viscosity at a shear rate of 100 / s of 1000 to 10000 mPa · A method for producing a gas diffusion layer for a fuel cell, wherein the ink of s is applied.
PCT/JP2010/068849 2009-12-18 2010-10-25 Gas diffusion layer for fuel cell, and membrane electrode assembly using said gas diffusion layer for fuel cell WO2011074327A1 (en)

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