Gas diffusion layer (GDL) / carbon paper is a porous carbon-fiber sheet used in fuel cells. It distributes reactant gases evenly to the catalyst layer, removes excess water to prevent flooding, and conducts electrons and heat. The product features high porosity, strong electrical and thermal conductivity, good mechanical strength, and controlled hydrophobicity through PTFE treatment. It also supports the catalyst-coated membrane and maintains stable contact under compression. Available in different thicknesses and densities, it ensures efficient mass transport, durability, and reliable performance in proton exchange membrane fuel cells and electrolyzers.