Low‐Temperature Construction of a Ti–O–C‐Linked S‐Scheme Heterojunction for Efficient Visible‐Light Photocatalytic Redox Reactions

The rational design of photocatalysts with superior efficiency and stability is essential for addressing the pressing global challenges of energy shortages and environmental remediation. However, the performance of conventional TiO₂ is limited by its wide bandgap and rapid charge recombination, while single-component photocatalysts generally exhibit restricted catalytic efficiency. Herein, a low-cost green synthesis strategy is developed to construct an S-scheme heterojunction through grafting of yeast-derived carbon dots (Y-CD) onto uncalcined anatase TiO₂ (UC-TiO₂) at 40°C via interfacial Ti─O─C bonds. The optimized heterojunction demonstrates exceptional visible-light photocatalytic activity, exhibiting reaction rate constants for Rhodamine B degradation and Cr(VI) reduction that are 29.5 and 60.2 times higher than P25-TiO₂, respectively. Recycling tests confirm excellent reusability and structural stability. Mechanism studies reveal that UC-TiO₂ possesses a small size and high surface area, contributing to high electron density and abundant active sites. Meanwhile, Y-CD not only extends visible-light absorption but also induces electronic states and intermediate energy levels that act as an energy-level bridge, facilitating S-scheme charge transfer. Driven by the built-in electric field and interfacial interactions, this pathway significantly promotes carrier separation and migration, thereby enhancing photocatalytic performance. This work demonstrates a sustainable route for developing high-performance photocatalysts for wastewater treatment.