High solar-to-hydrogen efficiency in the novel derivatives of group-III trichalcogenides for photocatalytic water splitting: the effect of elemental composition

Abstract

Two-dimensional (2D) materials with intrinsic electric fields (EF) are considered promising photocatalysts for hydrogen production from water splitting, but are still restricted by the solar-to-hydrogen (STH) efficiency. Here, we designed and investigated the derived 2D MNX₃ and MNXY₂ (M, N = In/Ga/Al; X, Y = S/Se/Te) monolayers as potential photocatalysts for water splitting applications. The light absorption of most MNX₃/MNXY₂ derivatives is significantly enhanced compared with their parent M₂X₃ monolayers. The introduction of Te with more diffuse valence orbitals than S/Se can effectively reduce the band gap of the MNX₃/MNXY₂ derivatives, enhancing their light absorption abilities. Some 2D MNX₃ and MNXY₂ monolayers with STH efficiencies ≥20% are further screened. Interestingly, driven by vacancy defects, the GaAlSSe₂-β monolayer can achieve the overall water-splitting process purely by the photoexcited carriers without the need for cocatalysts. Our work provides a prospective strategy for designing new highly efficient photocatalysts for water splitting applications based on the available parent materials by modulating the synergistic relation of bandgap, intrinsic EF, and overpotential.