Hydrogen Coverage-Driven Interfacial Water Restructuring Boosts Alkaline Hydrogen Oxidation

Hydrogen binding energy (HBE) is a key thermodynamic descriptor for the hydrogen oxidation reaction (HOR), yet its influence on the interfacial water structure in the electric double layer (EDL) and reaction kinetics, particularly as modulated by adsorbed hydrogen (H ad ) coverage, remains poorly understood. Here, we employ a WO 3 -supported Ir nanoparticle catalyst (WO 3 –Ir) to elucidate the impact of H ad coverage on the EDL structure and HOR kinetics in alkaline media. By integrating electrochemical measurements, in situ surface-enhanced infrared absorption spectroscopy, and theoretical calculations, we demonstrate that strong electronic interaction with WO 3 downshifts the Ir d-band center, thereby weakening the HBE and H ad coverage compared with pure Ir. This lower H ad coverage alleviates repulsive H ad –H 2 O interactions, facilitating hydrogen desorption and proton transfer. Simultaneously, the reduced H ad -induced surface hydrophobicity enhances water–electrode interactions and narrows the interfacial gap, thereby enriching asymmetric and weakly hydrogen-bonded water at the interface and forming a more connected interfacial water network that facilitates proton-coupled electron transfer across the EDL and accelerates alkaline HOR kinetics. These findings highlight the critical role of H ad coverage in modulating the interfacial water structure and in governing HOR kinetics in alkaline media.