Enhanced Hydrogen Adsorption on InO(111) via Oxygen Vacancy Engineering.

The emergence of InO as an efficient catalyst for selective hydrogenation has attracted significant attention. However, the mechanism of hydrogen (H) dissociation on InO remains experimentally elusive. In this work, we show that the interaction of H with InO is strongly influenced by the presence of oxygen vacancies. Using a combination of near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS), ultraviolet photoelectron spectroscopy (UPS), infrared reflection absorption spectroscopy (IRRAS), and density functional theory (DFT) calculations, we systematically investigated the interaction of H on well-defined oxidized InO(111) and partially reduced InO (111) surfaces. Our results reveal that H dissociates and adsorbs as hydroxyl groups (OH), which are exclusively stabilized on the InO (111) surface. The adsorbed hydrogen species act as electron donors, contributing to interfacial electron accumulation near the surface and inducing downward band bending. DFT calculations further indicate that oxygen vacancies in InO (111) are critical for facilitating the heterolytic dissociation of H, leading to the stabilization of In-H and OH species. These findings provide valuable implications for the catalytic behavior of indium oxide in hydrogenation and hydrogen-involved redox reactions.