Mono- and Bilayer ZnSnN₂ Sheets for Visible-Light Photocatalysis: First-Principles Predictions

The search for two-dimensional semiconductor materials suitable for visible-light photocatalysis is an active research field. In this work, using first-principles calculations, we explore the stability, electronic structure, and optical property of monolayer and bilayer ZnSnN 2 sheets. The phonon spectra confirm their dynamical stability. The PBE0 hybrid functional calculations predict that monolayer and bilayer ZnSnN 2 are direct-band gap semiconductors with band gaps of 2.39 and 2.62 eV, respectively. Based on band alignment and optical property calculations, we find that monolayer and bilayer ZnSnN 2 possess not only sufficient band gaps but also appropriate band edge positions for photocatalytic water splitting in the visible light region. Moreover, the band gaps and band edge positions of monolayer and bilayer ZnSnN 2 can be effectively tuned by applying biaxial strain, which may enhance photocatalytic performance. Our results provide guidance for experimental synthesis efforts and future application of two-dimensional ZnSnN 2 sheets.