In-situ nitrogen-doped black TiO2 with enhanced visible-light-driven photocatalytic inactivation of Microcystis aeruginosa cells: Synthesization, performance and mechanism

A series of nitrogen-doped black TiO2 nanocatalysts were successfully synthesized by a one-step method. It is novel to find that calcination in an N-2 atmosphere completed N doping and oxygen vacancies production simultaneously. In contrast, the urea addition as N precursor inhibited the nitrogen incorporation and the oxygen vacancies production. However, it is the sample using urea as N precursor that had the higher visible-light absorption, the narrower bandgap, the more efficient excited charges separation and higher degradation efficiency for removing chlorophyll-a in Microcystis aeruginosa algae cells. Mechanism exploration indicated that the intermediate energy states existed within the bandgap of TiO2, and center dot O-2(-) and center dot OH were the dominant radicals responsible for algae cell damage and organic matter degradation. This research will provide additional insight into the roles of N precursors and a calcining atmosphere to improve the photocatalytic activity of nitrogen-doped black TiO2 for algae inactivation and metabolites degradation.