Abstract
The emergence of In(2)O(3) as an efficient catalyst for selective hydrogenation has attracted significant attention. However, the mechanism of hydrogen (H(2)) dissociation on In(2)O(3) remains experimentally elusive. In this work, we show that the interaction of H(2) with In(2)O(3) is strongly influenced by the presence of oxygen vacancies. Using a combination of in situ 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(2) on well-defined oxidized In(2)O(3)(111) and partially reduced In(2)O(3-x) (111) surfaces. Our results reveal that H(2) dissociates and adsorbs as hydroxyl groups (OH), which are exclusively stabilized on the In(2)O(3-x) (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 In(2)O(3-x) (111) are critical for facilitating the heterolytic dissociation of H(2), 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.