Precisely Engineered Band Edges of Phase-Selectively Reduced TiO 2 via Dual Doping for Antimicrobial Photocatalysis with Enhanced Indoor Light Harvesting

Bacterial contamination of natural waters poses a serious threat to public health, and a TiO₂-based photocatalyst has been explored as one of the promising solutions to address this challenge. However, its practical application remains limited by the wide band gap, weak visible-light response, and rapid charge recombination. Here, we report a selectively disordered TiO₂-based dual strategy that integrates selective anatase reduction with S and Cu codoping (Cu-S-BTO). Selective reduction generated stable oxygen vacancies that enabled effective dopant incorporation and were preserved after doping, leading to a narrow band gap, enhanced charge separation, and improved visible-light harvesting. Under low-energy indoor light (700 lx), Cu-S-BTO achieved 99.9% antibacterial efficiency against four bacterial and one fungal strains while maintaining cytocompatibility with human skin cells. Moreover, in natural water samples from a valley, stream, and lake, Cu-S-BTO induced rapid 3-4 log bacterial reductions. This catalyst offers a practical and scalable solution for antimicrobial applications.