Theoretical Understanding of the Structure–Property Relationship of Oxygen-Doped Gallium Selenide as an Efficient Photocatalyst for Oxygen Evolution Reaction

A single-layer of GaSe is widely regarded as one of the most promising photocatalysts for a solar-driven water-splitting reaction. However, its catalytic performance is limited by the high onset potential for the oxygen evolution reaction (OER). Achieving the ideal adsorption strength of each intermediate (HO*, O*, and HOO*) involved in the OER process simultaneously via the surface modification of two-dimensional (2D) materials is a significant challenge. In this study, the effects of partial replacement of Se atoms of GaSe with O atoms on the catalytic activity of the resulting 2D GaSe1–xOx surface toward OER have been systematically examined using density functional theory calculations. Our theoretical results revealed that manipulating the atomic configuration of O dopants largely improves the catalytic activity of GaSe1–xOx. When the O-dopants are separated by a −Ga–Se–Ga– unit, the OER is limited by the strong adsorption of the O* intermediate. On the contrary, when a −Ga– unit is bonded with three O-dopants, this O-saturated Ga atom serves as the best site to initiate the OER and exhibits high catalytic performance with a predicted overpotential of 0.38 V, which is comparable with the values of many state-of-the-art precise-metal-based catalysts.