Water permeation through gas diffusion layers of proton exchange membrane fuel cells

► Water permeation properties of commercial carbon papers are studied. ► The permeation threshold increases with thickness and PTFE loading. ► There was a significant reduction of the permeation threshold after the first repetition. ► The apparent permeability was not a function of GDL thickness. ► The majority of pores in the tested GDLs were not filled with water to hinder the reactant access to the catalyst layer.