Alleviating the competitive adsorption of hydrogen and hydroxyl intermediates on Ru by d–p orbital hybridization for hydrogen electrooxidation†

Abstract

Strengthening the hydroxyl binding energy (OHBE) on Ru surfaces for efficient hydrogen oxidation reaction (HOR) in alkaline electrolytes at the expense of narrowing the effective potential window (EPW) increases the risk of passivation under transient conditions for the alkaline exchange membrane fuel cell technique. Herein, an effective Ru/NiSe₂ catalyst was reported which exhibits a gradually enhanced intrinsic activity and slightly enlarged EPW with the increased degree of coupling between Ru and NiSe₂. This promotion could be attributed to the optimized electron distribution and d-band structures of Ru surfaces weakening the hydrogen binding energy and especially the OHBE through the strong d–p orbital hybridization between Ru and NiSe₂. Unlike the conventional way of strengthened OHBE enhancing the oxidative desorption of hydrogen intermediates (H_ad) via the bi-functional mechanism, the weakened OHBE on this Ru/NiSe₂ model catalyst alleviates the competitive adsorption between H_ad and the hydroxyl intermediates (OH_ad), thereby accelerating the HOR kinetics at low overpotentials and hindering the full poisoning of the catalytic surfaces by strongly adsorbed OH_ad spectators at high overpotentials. The work reveals a missed but important approach for Ru-based catalyst development for the fuel cell technique.