A dual S-scheme heterojunction SrTiO₃/SrCO₃/C-doped TiO₂ as H₂ production photocatalyst and its charge transfer mechanism

Constructing an S-scheme heterojunction is a highly effective approach for enhancing photocatalytic performance. However, the impact of a single S-scheme heterojunction on charge transfer is limited. To overcome this constraint, a dual S-scheme heterojunction, SrTiO₃/SrCO₃/C-doped TiO₂ (referred to as ST/SC/CT), is designed for UV-vis-driven hydrogen production. The mass-normalized and effective surface area-normalized hydrogen production activities of ST/SC/CT are higher than those of ST and CT, respectively. The enhancement in photocatalytic performance is primarily attributed to the improved separation and transfer of photogenerated charge carriers by the dual S-scheme heterojunction. Moreover, C-doping effectively extends the light absorption range from UV to visible and greatly improves the absorption intensity. The heterojunction and charge transfer mechanism are also investigated through microscopy and spectroscopic techniques, as well as density functional theory (DFT) calculations. This work offers valuable insights for the design of novel composites by combining surface modification with heterojunction engineering.