Strain-engineered ZrSSe/Ga2SSe vdW heterostructure with enhanced visible light harvesting and high solar-to-hydrogen efficiency

Abstract

The growing global energy demand challenges the scientific community to develop innovative technologies, including the design of van der Waals (vdW) heterostructures, to address this issue. In response, we constructed a ZrSSe/Ga₂SSe vdW heterostructure by stacking ZrSSe on Ga₂SSe monolayers and investigated its potential applications in optoelectronics and as a photocatalyst for water splitting using first-principles calculations. The stability of this vdW heterostructure was confirmed through binding energy calculations and ab initio molecular dynamics (AIMD) simulations, further supported by determining various elastic coefficients, which demonstrated its mechanical stability. The calculated indirect band gap revealed a Type-I band alignment that can shift to Type-II by applying tensile biaxial strain up to 4 %. A substantial electrostatic potential drop (7.21 eV) across the ZrSSe/Ga₂SSe interface is expected to inhibit electron-hole pair recombination and facilitate effective separation, thereby enhancing photocatalytic activity. Notably, under tensile strain, the band edges of this heterostructure straddle the water redox potential at pH = 7, solar energy utilization is demonstrated by the high efficiency of solar-to-hydrogen conversion (17.64 %) at tensile strain of 1 %. The Gibbs free energy of HER is also calculated, indicating promising potential for experimental preparation as a photocatalyst. Moreover, our findings suggest that the ZrSSe/Ga₂SSe vdW heterostructure exhibits significantly stronger optical activity than the individual monolayers, with strain-enhanced absorption covering the ultraviolet, visible, and infrared regions, reaching a maximum light absorption value of 3 × 10⁵ cm⁻¹ in the visible range at 6 % strain. Consequently, this newly designed ZrSSe/Ga₂SSe vdW heterostructure demonstrates substantial potential for solar energy conversion applications and serves as a promising photocatalyst for water splitting.