High solar-to-hydrogen efficiency in AsP/GaSe heterojunction for photocatalytic water splitting: A DFT study

Abstract

Photocatalytic water splitting hydrogen production is a promising method to cope with the environmental issue and energy crisis, where the key factor is seeking high efficient photocatalysts. Here, the AsP/GaSe heterojunction is designed and its stacking configurations, energetic stability, electronic properties and strain effects are systematically studied. The results show that the AsP/GaSe heterojunction has a type-Ⅱ band alignment, which is beneficial to the separation of photogenerated electron-hole pairs. Moreover, the band edges of the heterojunction can straddle the redox potentials of water. The solar-to-hydrogen efficiency of the AsP/GaSe can reach a relatively high level, with a value of 28.3%. Furthermore, the optical and electronic properties of the AsP/GaSe heterojunction can be tuned when exerting strains. A red shift of the absorption spectrum in low energy region is observed under strains from −5% to 5%. The band alignment will transform from type-Ⅱ to type-Ⅰ under the strain of −5% ∼ −3% and 1%–5%. Under the compressive strain of −1% and −2%, the type-Ⅱ band alignment can be maintained. These results demonstrate that the AsP/GaSe heterojunction can be a promising photocatalyst for water splitting.