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

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 & GE;20% are further screened. Interestingly, driven by vacancy defects, the GaAlSSe2-& beta; 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.