Monoclinic Ga2O3 (100) surface as a robust photocatalyst for water-splitting

Abstract

The β-Ga₂O₃ (100) surface, with or without defects, as a robust photocatalyst for water decomposition was studied on the basis of density functional theory (DFT). The surface defects considered, herein, were oxygen vacancies and doping with higher chalcogens, such as S, Se and Te. Narrowed bandgaps of the defective surfaces, leading to a high utilization of solar energy with respect to pure Ga₂O₃, were observed. By optimizing the geometrical structures of the initial molecular adsorption states (IS), the transition states (TS) and the final dissociative adsorption states (FS), the reaction activation energy and the adsorption energy of each species in the reaction pathway were obtained. Water acts as a Lewis base and provides electrons to the surfaces. The presence of water on the surfaces more likely preferred the molecular modes. The reaction results demonstrate that the surface is robust for water decomposition, where the defects, both vacancies and doping with high chalcogens, have no evident influence on the reaction parameters. The reaction pathway can be improved by vacancies or Se doping. These findings for water decomposition on Ga₂O₃ (100) surfaces can be used in synthesis of photocatalysts and for understanding the interactions across the reaction pathway.