Asymmetric gas diffusion layers for improved water management in PGM-free electrodes.

Proton-exchange-membrane fuel cells (PEMFCs) offer a long-term, carbon-emission free solution to the energy needs of the transportation sector. However, high cost continues to limit PEMFC commercialization. Replacing expensive platinum group metal (PGM) catalysts with PGM-free catalysts could reduce cost, but the low active site density of PGM-free catalysts necessitates the use of thick electrodes that suffer from substantial mass transport losses. In these thick PGM-free electrodes, effective water management and oxygen transport are crucial to achieve high performance. In this work, we investigate the role of anode and cathode gas diffusion layer (GDL) configurations in controlling water management. Asymmetric GDL configurations, in which the anode GDL exhibits higher permeability than the cathode GDL, showed higher performance compared to conventional symmetric configurations. Computational modeling showed that the improved performance is mainly due to improved water management, resulting in lower liquid water saturation and faster oxygen transport in the cathode.