Effects of MEA Fabrication and Ionomer Composition on Fuel Cell Performance of PGM-free ORR Catalyst

Carbon-based platinum group metal-free (PGM-free) catalysts for oxygen reduction reaction (ORR) have received increasing attention as potential candidates for low-cost fuel cell cathode catalysts. Mass-transport within the very thick catalyst layer (CL) presents a major challenge to further improve the fuel cell performance of PGM-free catalysts, which may be realized through the optimization of CL structure. Herein, we demonstrate that membrane electrode assemblies (MEAs) with not hot-pressed PGM-free cathode showed improved H-2-air fuel cell performance in mass transport region when compared to MEAs prepared via hot-pressing technique. Further, the effects of the ionomer content and equivalent weight (EW) on fuel cell performance were systematically explored. We observed that an increase in ionomer content resulted in performance improvement in the kinetic region, while negatively affecting the performance in the mass transport region. The overall optimum fuel cell performance was achieved with an ionomer EW of 830 g mol(-1).