Porous carbon base material, method for preparation thereof, gas-diffusing material film-electrode jointed article, and fuel cell

A gas diffusion material, comprising:

• a porous carbon substrate comprising a sheet which includes short carbon fibers dispersed in random directions and a carbonized resin binding the short carbon fibers,
• wherein the sheet has pores;
• the volume of pores having pore sizes of 10 μm and less among the pores, per unit weight of the sheet, is in the range of 0.05 to 0.16 cc/g;
• and
• a water repellent material added to the substrate.

A fuel cell which comprises a membrane-electrode assembly, the membrane-electrode assembly comprising:

• a solid polymeric electrolyte membrane;
• catalyst layers containing catalyst-loaded carbon provided on both of the surfaces of the membrane;
• and
• gas diffusion materials provided in contact with both of the catalyst layers,
• wherein at least one of the gas diffusion materials is a gas diffusion material comprising a water repellent material added to the substrate and a porous carbon substrate comprising a sheet which includes short carbon fibers dispersed in random directions and a carbonized resin binding the short carbon fibers, the sheet having pores, and the volume of pores having pore sizes of 10 μm and less among the pores, per unit weight of the sheet, being in the range of 0.05 to 0.16 cc/g.