Membrane electrode structure for polymer electrolyte fuel cell

Abstract

A membrane electrode structure for a polymer electrolyte fuel cell capable of offering excellent power generation performance both in high humidity conditions and low humidity conditions. The membrane electrode structure for a polymer electrolyte fuel cell is composed of a solid polymer electrolyte membrane 2 having proton conductivity, a cathode electrode catalyst layer 3, an anode electrode catalyst layer 4 and gas diffusion layers 5, 6. The gas diffusion layers 5, 6 have through holes with a mean diameter of 15 to 45 μm and a specific surface area of 0.25 to 0.5 m2/g, and have a bulk density of 0.35 to 0.55 g/cm3. An intermediate layer 7 is provided between the cathode electrode catalyst layer 3 and the gas diffusion layer 5, and the intermediate layer 7 has through holes with a diameter of 0.01 to 10 μm and a volume of 3.8 to 7.0 μl/cm2. The intermediate layer 7 is made of a water-repellent resin containing conductive particles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a configuration of the membrane electrode structure of the present invention;

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a fuel cell using the membrane electrode structure shown in FIG. 1; and

FIG. 3 is a graph showing the relationship between the volume of pores in the intermediate layer on the cathode side of the membrane electrode structure of the present invention and terminal voltage.

Claims

1. A membrane electrode structure for a polymer electrolyte fuel cell comprising a solid polymer electrolyte membrane having proton conductivity, a cathode electrode catalyst layer provided on one side of the solid polymer electrolyte membrane, an anode electrode catalyst layer provided on the other side of the solid polymer electrolyte membrane, and a gas diffusion layer provided on a side of the respective electrode catalyst layers opposite from the solid polymer electrolyte membrane, wherein the gas diffusion layer has pores with a mean diameter of 15 to 45 μm and a specific surface area of 0.25 to 0.5 m2/g, which extend through the gas diffusion layer in the thickness direction, and has a bulk density of 0.35 to 0.55 g/cm3.

2. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the pores extending through the gas diffusion layer in the thickness direction have a mean diameter of 15.8 to 21 μm.

3. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the pores extending through the gas diffusion layer in the thickness direction have a specific surface area of 0.33 to 0.46 m2/g.

4. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the gas diffusion layer has a bulk density of 0.37 to 0.46 g/cm3.

5. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 1, wherein the gas diffusion layer comprises water repellent-treated carbon paper.

6. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 1, further comprising an intermediate layer at least part of which is embedded in the gas diffusion layer formed between the cathode electrode catalyst layer and the gas diffusion layer provided on the cathode electrode catalyst layer,wherein the intermediate layer has pores with a diameter of 0.01 to 10 μm and a volume of 3.8 to 7.0 μl/cm2, which extends through the intermediate layer in the thickness direction.

7. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 6, wherein the intermediate layer comprises a water repellent resin containing conductive particles.

8. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 7, wherein the conductive particles are carbon powder.

9. The membrane electrode structure for a polymer electrolyte fuel cell according to claim 7, wherein the water-repellent resin is tetrafluoroethylene.