Two-dimensional CrSe2/GaN heterostructures for visible-light photocatalysis with high utilization of solar energy

Nowadays, designing a two-dimensional (2D) van der Waals heterostructure (vdWH) is one of the most promising methods for improving photocatalytic performance and harvesting solar energy. Here, we proposed a novel CrSe2/GaN vdWH as an efficient photocatalyst for overall water splitting. The elastic constants, phonon dispersion, and ab-initio molecular dynamics simulation show high mechanical and thermodynamic stability. The HSE06 functional reveals that CrSe2/GaN vdWHs possess a direct bandgap. The DFT scheme suggests that the current vdWH belongs to the type-II band alignment and has enough kinetic redox potentials for overall photocatalytic water splitting. The intrinsic electric-field accelerates the photogenerated carrier separation. The carrier mobility of the CrSe2/GaN vdWH is observed to be enhanced as compared to the mobility of the CrSe2 monolayer. Additionally, the optical absorption of the vdWH is found to be high in the visible and ultraviolet regions. The CrSe2/GaN vdWH has a high efficiency of solar-to-hydrogen energy conversion (33.41%). The Gibbs free energy shows that the redox reactions (HER & OER) could be sustained under the action of an external electric-field. Finally, the external strain can tune the band edge and optical absorption of the CrSe2/GaN vdWH for desired applications. Therefore, the CrSe2/GaN vdW heterostructure could be an excellent photocatalyst for water splitting with high solar energy conversion.