Influence of MPL Structure Modification on Fuel Cell Oxygen Transport Resistance

Abstract

In this work the dependence of limiting current on gas pressure and temperature was measured to separate the oxygen transport resistance into its components: molecular diffusion resistance in the gas diffusion layer (GDL) and resistance in the catalyst layer (CL), which comprises Knudsen diffusion resistance and oxygen permeation resistance through ionomer. The effect of microporous layer (MPL) modification by laser perforation on the oxygen transport resistances was investigated. The resistance in CL contributed a significant portion, about one quarter, to the total oxygen transport resistance. A trend of decreasing CL resistance with increasing temperature was observed. This temperature effect was mainly attributable to the oxygen permeation in CL ionomer. The MPL modification had little influence on the total transport resistance as well as its individual component for the cells under dry operation, while the perforated MPL significantly reduced the transport resistance when water starts to condense in electrode. This finding indicated that the MPL plays important roles in the cathode water management.