Gas diffusion composite material for fuel cells, and polymer electrolyte fuel cell

A gas diffusion composite material for fuel cells, the gas diffusion composite material comprising:

• a porous substrate sheet including a conductive material;
• and
• a microporous carbon layer containing a particulate and/or fibrous carbon material and a water-repellent resin,
• wherein
• the porous substrate sheet is a sheet-like member having a plurality of through-holes including a conductive material,
• a material of the porous substrate sheet is a carbon material,
• a form of the porous substrate sheet is a mesh sheet, a punching sheet, or an expanded sheet,
• the porous substrate sheet has a thickness of 5 μm or more and 100 μm or less, and
• the gas diffusion composite material has any one of the following structures (A) to (E):
• structure (A):
• a structure in which one surface of the porous substrate sheet is coated with the microporous carbon layer,
• structure (B):
• a structure in which both surfaces of the porous substrate sheet are coated with the microporous carbon layer,
• structure (C):
• a structure in which the microporous carbon layer covers one surface of the porous substrate sheet, and a part of the microporous carbon layer penetrates into the porous substrate sheet, and the microporous carbon layer does not reach from the one surface to the opposite surface of the porous substrate sheet,
• structure (D):
• a structure in which the microporous carbon layer covers one surface of the porous substrate sheet, a part of the microporous carbon layer penetrates into the porous substrate sheet, and the microporous carbon layer reaches from one surface to the opposite surface of the porous substrate sheet, and
• structure (E):
• a structure in which the entire porous substrate sheet is embedded in the microporous carbon layer.

A gas diffusion composite material for fuel cells, the gas diffusion composite material comprising:

• a porous substrate sheet including a non-conductive material;
• and
• a microporous carbon layer containing a particulate and/or fibrous carbon material and a water-repellent resin,
• wherein
• the porous substrate sheet has a thickness of 3 μm or more and 150 μm or less, and
• the gas diffusion composite material has the following structure (D) or (E):
• structure (D):
• a structure in which the microporous carbon layer covers one surface of the porous substrate sheet including the non-conductive material, a part of the microporous carbon layer penetrates into the porous substrate sheet including the non-conductive material, and the microporous carbon layer reaches from one surface to the opposite surface of the porous substrate sheet including the non-conductive material, and
• structure (E):
• a structure in which the entire porous substrate sheet is embedded in the microporous carbon layer.