Surface and Interface Engineered Hydrated Nickel Hydroxide on Nickel Enables Rapid Active Species Shuffling in Alkaline Hydrogen Electrocatalysis

Abstract

Achieving acid-like hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) activity in alkaline media using low-cost, non-precious metal catalysts is essential for energy conversion technologies. Here, we demonstrate the indispensable role of water within the catalyst layer in enhancing HOR/HER kinetics, mediated by hydrated and dehydrated oxophilic sites on nickel (Ni) catalysts coated with nickel hydroxide (Ni(OH)2). Electrochemical measurements combined with density functional theory (DFT) calculations show that an acid-like environment creates at the electrified interface through water molecules that bridge active hydrogen and oxygen species within the catalyst surface layer. This interfacial behavior differs from that described in conventional bulk and interface models. Our findings highlight the importance of interfacial hydrogen bonding network across the interface in hydrogen electrocatalysis and provide guidance for the design of efficient catalysts for alkaline fuel cell and electrolyzer applications.