Platinum-free electrocatalysts for hydrogen oxidation reaction in alkaline media

Abstract

The renewed anion exchange membrane fuel cells (AEMFCs) are expected to minimize the cost constraints of fuel cells owing to the advantages of employing economic catalysts. However, high Pt dosage (almost ten times higher than that in acids) caused by the sluggish hydrogen oxidation reaction (HOR) kinetics in alkaline media hampers the development of AEMFCs. Developing alternative Pt-free electrocatalysts is desirable but is limited by the lack of mechanistic understanding and system-wide design guidance. Against this backdrop, this review starts with the alkaline HOR mechanisms about reaction pathways, hydrogen/hydroxyl binding energy theory, and theoretical interpretations on the low HOR kinetics in alkali. Next, recent advances in developing supports, cocatalysts, and active components for Pt-free HOR catalysts are summarized. The synergistic mechanism of supports and cocatalysts with active metals is for the first time systematically introduced. Finally, a brief perspective on the remaining challenges and future directions of Pt-free electrocatalysts for alkaline HOR is also outlined.