Abstract: A porous carbon sheet contains carbon fiber and a binder, wherein the carbon sheet is characterized in that in a section from a plane having a 50% filling ratio closest to one surface to a plane having a 50% filling ratio closest to the other surface, when letting layer X be a layer with the largest filling ratio close to the one surface, layer Y be a layer with a filling ratio smaller than layer X close to the other surface, and layer Z be the layer positioned between layer X and layer Y for layers obtained by dividing the carbon sheet equally into three in a direction perpendicular to the surfaces, the filling ratio for the layers becomes smaller in order of layer X, layer Y, and layer Z.

Abstract: A porous carbon sheet includes a carbon fiber and a binding material, wherein when in a measured surface depth distribution, a ratio of an area of a portion having a depth of 20 ?m or less in a measured area of one surface is a surface layer area ratio X, and a ratio of an area of a portion having a depth of 20 ?m or less in a measured area of another surface is a surface layer area ratio Y, the surface layer area ratio X is larger than the surface layer area ratio Y, and a difference between the surface layer area ratios is 3% or more and 12% or less.

Abstract: A gas diffusion electrode substrate that is used in a fuel cell, wherein a microporous layer constituted by a carbon based filler and a fluororesin is formed on one surface of the electrode substrate, the sliding angle of water on the surface on the opposite side of the surface on which the microporous layer is formed is 30 degrees or less, and the through-plane gas permeation resistance is 15 to 190 mmAq.

Abstract: A gas diffusion electrode substrate that, is used in a fuel cell and is constituted by an electrode substrate and microporous parts, in which a microporous part (A) is formed on one surface of the electrode substrate, and a microporous part (B) is formed in a part, of the inside of the electrode substrate, the gas diffusion electrode substrate having a part in which the microporous part (B) is continuously present from the electrode substrate surface on the side on which the microporous part (A) is formed to a position near the electrode substrate surf ace on the opposite side, and a part in which pores are continuously distributed front the electrode substrate surface on the side on which the microporous part (A) is formed to the electrode substrate surface on the opposite side.

Abstract: A gas diffusion electrode substrate that is used in a fuel cell and is constituted by an electrode substrate and microporous parts, in which a microporous part (A) is formed on one surface of the electrode substrate with a thickness in the range of 10 ?m or more and 60 ?m or less, and in the gas diffusion electrode substrate, the pore volume of pores with a pore size of 0.1 ?m or more and less than 10 ?m is within the range of 0.9 times or more and 5 times or less of the pore volume of pores with a pore size of 10 ?m or more and less than 100 ?m.

Abstract: A fuel cell gas diffusion electrode medium has exceptional anti-flooding characteristic and anti-dry-out characteristic, the capability to achieve high cell performance across a wide temperature range from low to high temperatures, and exceptional mechanical properties, electrical conductivity, and thermal conductivity, a microporous layer being arranged on one surface of an electrode base material; wherein the fuel cell gas diffusion electrode medium is characterized in that linear carbon having an aspect ratio of 30-5000 is included in the microporous layer, and the areal weight of the gas diffusion electrode medium is 30-60 g/m2.

Abstract: A gas diffusion electrode medium is for a fuel cell, has a low in-plane gas permeability and favorable water drainage characteristics in addition to high conductivity, and is able to exhibit high cell performance across a wide temperature range from low temperatures to high temperatures. The gas diffusion electrode medium is characterized by a microporous region being disposed at least at one surface of an electrode substrate, and the microporous region containing flake graphite having an aspect ratio of 50-5000.

Abstract: A gas diffusion medium for a fuel cell includes a microporous region [A], an electrode base material, and a microporous region [B] arranged in the order mentioned, wherein the microporous region [A] has an areal ratio of 5 to 70%, and the microporous region [B] has an areal ratio of 80 to 100%.