Direct Z-scheme Sc2CF2/SnS2 heterojunction with high solar-to-hydrogen efficiency for photocatalytic water splitting

Rational design of two-dimensional (2D) van der Waals (vdW) heterojunction enables effective separation of photogenerated carriers, providing a viable solution for low photocatalytic efficiency of single-component 2D materials. Herein, a novel Sc₂CF₂/SnS₂ heterojunction was designed and its feasibility as a photocatalyst for solar-driven water splitting was comprehensively investigated using first-principles calculations. The Sc₂CF₂/SnS₂ heterojunction exhibits type-II staggered band alignment with band edges straddling water splitting redox potentials, while interfacial charge transfer pathway follows a direct Z-scheme mechanism. By integrating the optical merits of Sc₂CF₂ and SnS₂ monolayers, the Sc₂CF₂/SnS₂ heterojunction attains enhanced spectral response and remarkable solar-to-hydrogen (STH) efficiency of 42.40 %. Thermodynamic spontaneity of overall photocatalytic water splitting is demonstrated on the Sc₂CF₂/SnS₂ surface within a pH range of 5.60–12.37. Furthermore, within the 0 %–4 % strain window, the band edges of the Sc₂CF₂/SnS₂ heterojunction satisfy the thermodynamic requirements for solar-driven water splitting across acidic, neutral and alkaline environments. External electric fields further enable precise modulation of the bandgap and band edges, offering tunable photocatalytic performance. These findings suggest the significant potential of the Sc₂CF₂/SnS₂ heterojunction for solar-driven water splitting and provide new strategies for developing high-efficiency photocatalysts.