Analysis of Oxygen Concentration Distribution in a PEFC with Oxygen Quenching Dye (Investigation of Basic Characteristics and Measurement of Oxygen Concentration Distribution on Gas Diffusion Layer)

A measuring technique of oxygen concentration distribution on the gas diffusion layers (GDLs) along the cathode gas flow channels in polymer electrolyte fuel cells (PEFCs) has been developed. Oxygen quenching phosphorescent paint prepared by dissolving dye (PtTFPP) and binder in toluene is sprayed by air on a GDL, which is installed in a transparent PEFC, and excited by ultraviolet light. The phosphorescence of the GDL is measured with a CCD camera having an image intensifier through a 650 nm sharp cut color filter. Stern-Volmer coefficients Ksv under the operating condition (in-situ) are estimated from phosphorescent intensity for no oxygen quenching I0 with nitrogen gas supplied in the cathode and that for oxygen quenching I with air in the cathode at open circuit voltage. By obtaining Ksv at each measuring point, the irregularity of the air spray painting and the error due to product water wetting are cancelled. Measured oxygen concentration distribution deviates from the theoretical values at some characteristic points, suggesting cathode gas short cut between the separator rib and GDL.