First-principles study of the Sc2CF2/WS2 heterostructure: Electronic structure and strain effects

Abstract

This study, based on first-principles density functional theory calculations, explores the stability, electronic structure, and optical properties of the Sc2CF2/WS2 heterostructure, with particular emphasis on analyzing its properties under strain effects. Results show it has an indirect bandgap of 1.416 eV—smaller than 1.886 eV of Sc2CF2 and 2.311 eV of WS2 monolayers—and adopts a Z-scheme heterojunction. A 7.861 eV built-in electric field from Sc2CF2 to WS2 promotes efficient electron transfer. Compared with monolayers, it has significantly enhanced optical absorption: Its ultraviolet absorption coefficient reaches 17.9 × 105 cm−1 (250.9% higher than Sc2CF2) and visible-region absorption coefficient is 0.86 × 105 cm−1 (16.2% higher than Sc2CF2). At pH = 0, its band edges cross water’s redox potential, enabling hydrogen/oxygen evolution. For −6% to 6% biaxial strain: −6% to −3% compressive strain turns it into type-I, which is bad for photocatalysis; −2% to 2% retains Z-scheme, suitable for pH = 0 photocatalysis with a maximum built-in electric field of 7.927 eV at −1% strain; and 3% to 6% shifts band edges upward, suitable for pH = 7 while preserving Z-scheme. Moreover, strain engineering further enhances the optical absorption coefficient. These findings confirm its excellent photocatalytic performance, validate strain engineering, and guide MXene/transition metal dichalcogenides-based photocatalyst design.