Rational Design of Multimodal Porous Carbon for the Interfacial Microporous Layer of Fuel Cell Oxygen Electrodes.

Accumulation of water at the interface of the cathode catalyst layer (CCL) and the diffusion media is a major cause of performance loss in H2/air fuel cells. Proper engineering of the interface by the use of advanced materials and preparation methods can effectively reduce the extent of this loss by improving the transport of water and gas across this interface. Herein, we present detailed modeling results of water and gas transport across this interface for in-house synthesized carbon material with multiple levels of porosity and by considering the interfacial properties of the carbon material and the microporous layer (MPL). The oxygen reduction reaction and the counter-flow transport of oxygen and water within the CCL and MPL pores were modeled considering a partially flooded interface. Well-characterized multimodal porous carbon was chosen as a candidate material for this study, and the effects of all the various levels of porosity in the MPL, wettability, permeability, and the quality of contact between the MPL and CCL on the transport phenomena of fluids were investigated. This study provides new insights into the balance of opposing transport phenomena on the local and overall performance of the catalyst layer and rationalizes the design parameters for an MPL material based on both the material and interfacial properties.