Study on hydrophobicity loss of the gas diffusion layer in PEMFCs by electrochemical oxidation

Abstract

The hydrophobicity loss of the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) was investigated by an accelerated stress test of electrochemical oxidation at a constant potential. The fresh and oxidized GDLs were characterized by cyclic voltammetry, contact angle measurements and water permeability. Results showed the occurrence of the oxidation of carbon and the decrease of the hydrophobicity of GDL. To discuss the reasons for the hydrophobicity loss, scanning electron microscopy, X-ray photoelectron spectroscopy and thermogravimetry were analyzed. It was found that the hydrophobicity loss was closely associated with the losses of the carbon materials and polytetrafluoroethylene (PTFE) in GDL under test conditions. In addition, the mass loss of carbon materials was more than that of PTFE.