Pristine and Janus chromium dichalcogenides: Potential photocatalysts for overall water splitting in wide solar spectrum under strain and electric field

Abstract

Two-dimensional (2D) materials have been considered as promising applicants, to address the existing energy crisis, for solar energy conversion and photocatalytic water splitting. Here as efficient photocatalysts for water splitting under a wide spectrum from near-infrared, visible to ultraviolet radiation, chromium pristine and Janus monolayers are proposed. A comprehensive investigation of electronic and optical properties of CrS2, CrSe2 and CrTe2 pristine dichalcogenide, CrSSe, CrSTe and CrSeTe Janus monolayers under biaxial strain and electric field using ab-initio method are presented. Binding energy, phonon spectrum and elastic constants illustrate their high dynamic and mechanical stability. The hybrid functional (HSE06) is employed to accurately assess the electronic properties of all monolayers. Band alignment investigation using empirical and DFT methods have revealed that CrSe2 and all Janus monolayers are potential candidates for photocatalytic overall splitting of water. All dichalcogenides and Janus structures have high optical absorption coefficients (~1.0–1.4 ×105 cm−1) which lies from infrared to UV region. Furthermore, it is also observed that due to increase in applied strain, the bandgaps almost decrease linearly. Conversely, there is no significant influence of external electrical field on pristine and Janus dichalcogenides except CrSTe and CrSeTe monolayers. While, strong absorption intensity is slightly increased and move towards high energy in ultraviolet region. Present work not just only highlights the photocatalytic efficiency of pristine CrA2 (A=S, Se, Te) and Janus CrAB (A/B= S, Se, and Te, A≠ B) monolayers but also offers an approach to tune the electronic and optical properties by strain and external electrical field engineering.