Abstract: To provide a gas diffusion layer that allows reducing an increase in contact resistance with a separator and also allows reducing deterioration of gas diffusivity. The gas diffusion layer is disposed in contact with a separator including a grooved fluid flow passage. The gas diffusion layer includes a diffusion layer substrate and a water-repellent layer. The diffusion layer substrate has a ratio of a pore diameter to a thickness of 0.35 or more. The water-repellent layer is disposed on a surface of the diffusion layer substrate. The diffusion layer substrate is made of a carbon fiber. A content rate of the carbon fiber is 30% or more.

Abstract: A water-repellent layer for fuel cell contains a water-repellent material and a hydrogen peroxide decomposition catalyst. A mass ratio of the hydrogen peroxide decomposition catalyst to the water-repellent material is between 5 mass percent and 20 mass percent, inclusive.

Abstract: To provide a gas diffusion layer that allows reducing an increase in contact resistance with a separator and also allows reducing deterioration of gas diffusivity. The gas diffusion layer is disposed in contact with a separator including a grooved fluid flow passage. The gas diffusion layer includes a diffusion layer substrate and a water-repellent layer. The diffusion layer substrate has a ratio of a pore diameter to a thickness of 0.35 or more. The water-repellent layer is disposed on a surface of the diffusion layer substrate. The diffusion layer substrate is made of a carbon fiber. A content rate of the carbon fiber is 30% or more.

Abstract: A water-repellent layer for fuel cell contains a water-repellent material and a hydrogen peroxide decomposition catalyst. A mass ratio of the hydrogen peroxide decomposition catalyst to the water-repellent material is between 5 mass percent and 20 mass percent, inclusive.

Abstract: A fuel cell includes a separator and a power generating body. The separator and power generating body are laminated each other. The power generating body is equipped at least with an electrolyte membrane. The fuel cell comprises: a sealing part that seals reaction gas supplied for electrochemical reactions at the fuel cell between the power generating body and the separator at an outer circumference part of the fuel cell, wherein a convex part and a recess are fit together in the sealing part. The convex part is formed projecting in the lamination direction on one of the power generating body and the separator, and the recess is formed recessed in the lamination direction on the other of the power generating body and the separator. At least one of the convex part and the recess is formed with a polymer material that expands with moisture absorption.

Abstract: A fuel cell includes a separator and a power generating body. The separator and power generating body are laminated each other. The power generating body is equipped at least with an electrolyte membrane. The fuel cell comprises: a sealing part that seals reaction gas supplied for electrochemical reactions at the fuel cell between the power generating body and the separator at an outer circumference part of the fuel cell, wherein a convex part and a recess are fit together in the sealing part. The convex part is formed projecting in the lamination direction on one of the power generating body and the separator, and the recess is formed recessed in the lamination direction on the other of the power generating body and the separator. At least one of the convex part and the recess is formed with a polymer material that expands with moisture absorption.