This study uses fuel Cell gas diffusion layers (GDLs) fabricated in the laboratory front carbon fiber cloth with different concentrations of hydrophobic agents in proton exchange membrane fuel cells (PEMFCs). and investigates the relationship between the hydrophobic agent content of (lie carbon fiber cloth and fuel cell performance. The paper examines the effect of hydrophobic agent content on GDL thickness, contact angle, an permeability, and Surface and through-plane resistivity. Carbon fiber cloth is impregnated with hydrophobic agent concentrations of 0, 3, 5, 10, 30, and 50 wt%, and the resulting GDLs ale subjected to performance tests. When file test piece area is 25 cm(2), the test temperature 80 C, the gasket thickness 0.36 mm. and the hydrophobic agent content 5 wt%, a fuel cell using the GDL. has a Current density of 1430 mA cm (2) at 0.3v. (C) 2009 Elsevier B.V. All rights reserved.