TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The carbon powder is active carbon, active carbon fiber, carbon black, carbon aerosol, carbon nanotube, carbon nanofiber, carbon nanohorn, and/or natural or synthetic graphite. The carbon powder has an average particle size of 20-2000 nm and a specific surface area of 20-2000 m2/g. The carbon substrate is carbon cloth, carbon paper, carbon felt, and/or carbon sheet.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The fluorinated resin is PTFE, tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), and/or polyvinylidene fluoride (PVDF). The fluorinated resin is used at 5-100 pbw/100 pbw carbon powder. The aqueous polymer resin is polymer resin that can be carbonized at 250-400degreesC under air or oxygen atmosphere. The dispersant is anionic, cationic, amphoteric and/or nonionic surfactant. Preferred Method: The carbon substrate is pre-treated with water repellent, e.g. PTFE, PFA, FEP, PCTFE, ETFE, or PVDF, by impregnating in water repellent solution followed by drying. EXAMPLE - Ultra pure water (1000 g) and Vulcan XC-72(RTM: not defined) were blended in a high-speed mixer (2000 rpm). Triton X-100(RTM: polyethylene glycol tert octylphenyl ether) was added and the components were dispersed for 1 hour. Carboxymethylcellulose (30 g) was added and the components were further dispersed for 1 hour. PTFE (30 wt.%) was added and the components were stirred in a low-speed mixer (200 rpm) for 1 hour to make carbon slurry. The PTFE content was adjusted to 30 pbw/100 pbw carbon powder. Carbon substrates were immersed in a PTFE suspension for 5 minutes and dried in 80degreesC dry oven for 1 hour so that the content of PTFE was 30 wt.%. The carbon slurry was coated on the carbon substrates and dried in 80degreesC dry oven for 1 hour to obtain primer layers with a thickness of 10 microns. The same carbon slurry was coated on the primer layers and dried to obtain gas diffusion layers with a total thickness of 40 microns. The gas diffusion layers were sintered in 350degreesC oven for 30 minutes.