On the presence of surface bound hydroxyl species on polycrystalline Pt electrodes in the “hydrogen potential region” (0–0.4 V-RHE)

The development of highly efficient electrocatalysts toward hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cells (AEMFCs). However, the HOR kinetics in alkaline is two to three orders of magnitude slower than that in acid. More critically, fundamental understanding of the sluggish kinetics derived from the pH effect is still debatable. In this review, the recent development of understanding HOR mechanism and rational design of advanced HOR electrocatalysts are summarized. First, recent advances in the theories focusing on fundamental understandings of HOR under alkaline electrolyte are comprehensively discussed. Then, from the aspect of intermediates binding energy, optimizing hydrogen binding energy (HBE) and increasing hydroxyl binding energy (OHBE), the strategies for designing efficient alkaline HOR catalysts are summarized. At last, perspectives for the future research on alkaline HOR are pointed out.