Recent advances in integrating platinum group metal-free catalysts in proton exchange membrane fuel cells

Abstract

Platinum group metal (PGM)-free catalysts are promising low-cost materials for the oxygen reduction reaction in proton exchange membrane fuel cells (PEMFCs). A variety of chemical precursors and synthesis methods have been proposed to increase their catalytic activity. In comparison, significantly less attention has been dedicated to the integration of these PGM-free catalysts into operating electrodes by investigating the role of the membrane electrode assembly (MEA) fabrication on the PEMFC performance. We discuss here some remarkable performance improvements recently achieved by tuning catalyst loading, ionomer content, and ink solvent composition, and call for further explorations of the ink processing and MEA fabrication to improve performance. • Thick PGM-free catalyst layers suffer from proton and mass transport limitations. • Improving the active site accessibility is as important as their turnover frequency. • Progresses in ink processing and MEA fabrication can improve the PEMFC performances. • Good interactions between ionomer and catalyst agglomerates are crucial.