Atomic Ti-Nx sites with switchable coordination number for enhanced visible-light photocatalytic water disinfection

Photocatalytic sterilization represents one of the promising strategies for efficient utilization of solar energy to remove hazardous materials, mainly based on the development of intrinsic materials with intact structures that actually cannot be absolutely remained under light irradiation but ignored in most cases. Herein, novel single titanium atoms anchored on g-C3N4 photocatalysts were facilely prepared by calcination of g-C3N4 with bis(cyclopentadienyl)dicarbonyl titanium. The introduction of single Ti atoms in g-C3N4 promoted photocatalytic efficiency by improving the separation efficiency of carriers with a broad visible-light-responsive range and reducing the energy barrier for the transfer of superoxide radicals to hydroxyl radicals. Especially, upon light-driven interaction with adsorbed O2, the photocatalyst coordination number could be remarkably regulated in situ from Ti–N6 to Ti–N4, which led to a more efficient generation of clean active substances in disinfectants (O2•− and •OH). As a result, the single Ti catalyst showed superior activity in the photocatalytic disinfection of bacteria and excellent recyclability. The inactivation of E. coli for the CN–Ti50 sample was 91.2% under irradiation for 30 min, which was 9.9 times that of pure g-C3N4. This in situ activation approach opens a new avenue for engineering efficient and energy-saving catalysts for water sterilization.