Directing photocatalytic pathway to exceedingly high antibacterial activity in water by functionalizing holey ultrathin nanosheets of graphitic carbon nitride

Metal-free polymeric carbon nitride (C3N4) photocatalysts offer attractive technological advantages over the conventional transition metal oxides or sulfides -based photocatalysts in water disinfection, but their antimicrobial activities are limited by their rapid charge carrier recombination and low specific surface areas. By controlling photocatalytic pathways, we obtained in amino-rich holey ultrathin g-C3N4 nanosheets (AHUCN) a highly efficient inactivation rate against E-coli, which is the highest among the monolithic g-C3N4 and exceeds the antibacterial performance of the most of the previously reported g-C3N4-based photocatalysts. Both the experiments and theoretical calculations demonstrated that the high photocatalytic disinfection performance of AHUCN was derived from the synergistic advantages of their unique holey ultrathin structure and the amino - rich surface in controlling the charge separation and transfer, and most importantly in increasing the photo-production of the dominant antibacterial species, H2O2. From the analysis of the reactive oxygen species and rotating disk electrode (RDE) measurements, it was found that the presence of abundant surface amino groups enabled the switch of the oxygen-reduction pathway from the two-step single-electron indirect reduction on holey ultrathin g-C3N4 nanosheets (HUCN) to the one-step two-electron direct reduction on AHUCN. The switch of the H2O2 production pathway not only facilitated the separation of photogenerated electron-hole pairs but also promoted the generation of reactive oxygen species, greatly enhancing photocatalytic disinfection efficiency.