Generation of Surface Ga-H Hydride and Reactivity toward CO2

Abstract

Hydrogen adsorption on gallium oxide was investigated by in situ infrared (IR) spectroscopy over a temperature range of 30–450 °C. Both hydroxyl groups and Ga-H hydrides with a pair of characteristic bands at 3685 (3532) cm^–1 and 2011 (1988) cm^–1 were detected on the surface gallium oxide. The formation and stability of surface Ga-H hydrides were found to be highly dependent on the temperature of H₂ dissociation. Through a combination of density functional theory (DFT) calculations and isotopic experiments, a mechanism involving both heterolytic and homolytic pathways for hydrogen dissociation was proposed for the generation of Ga-H hydrides. Furthermore, the reactivity of surface Ga-H hydrides was explored by their interactions with various probe molecules such as carbon dioxide, oxygen, and nitrogen. A potential reaction mechanism involving the attraction between nucleophilic hydrogen and positively charged intermediates was suggested during those hydrogenations.