(561a) Towards Establishing Apparent Hydrogen Binding Energy As the Descriptor for Hydrogen Oxidation/Evolution Reactions (Invited)

This perspective article formalizes our proposal that the apparent hydrogen binding energy (HBE_app), which takes into account of the water adsorption energy as well as the intrinsic hydrogen binding energy (HBE) on metal surfaces, is the descriptor for hydrogen oxidation/evolution reactions (HOR/HERs). We show that the HBE_app, not HBE, is pH dependent and can be determined from the underpotential-deposited hydrogen peaks in cyclic voltammograms for platinum group metals including Pt, Ir, Pd, and Rh, and the decrease of their HOR/HER activities with pH is the result of a strengthened HBE_app resulted from a weakened water adsorption. Also discussed are the needs of further experimental and theoretical work to prove this hypothesis.