Magnetic carbon nanotubes/red phosphorus/graphitic carbon nitride heterojunction for highly efficient visible-light photocatalytic water disinfection

The development of recyclable antimicrobial catalysts with high photocatalytic disinfection efficiency is urgently needed. To this end, a ternary heterojunction of magnetic carbon nanotubes/red phosphorus/graphitic carbon nitride (MCNTs/RP/CN) is designed and applied as a recyclable photocatalytic disinfectant for the first time. Significantly, the MCNTs/RP/CN outperforms the most-studied P25 TiO2 under both visible-light and real-sunlight illumination, and its disinfection efficiency ranks as one of the best among various CN-based catalysts developed previously. The bacterial inactivation processes, such as the membrane damage at metabolic and structural levels, the leakage of intracellular components, the entrance of extracellular reactive oxygen species (ROS) to cytoplasm, and the decomposition of genomic DNA, are thoroughly investigated. The characterization and theoretical calculation results corroborate the interfacial interaction between the three moieties in the heterojunction, and thus efficient charge transfer occurs, thereby enhancing the photocatalytic ROS generation amount for efficient water disinfection. The bacterial inactivation mechanism is investigated in a scavenger study, •O2− and H2O2 are identified as the major ROS for bacterial inactivation. In addition, the MCNTs/RP/CN shows applicability in the authentic water matrices, toward a variety of pathogenic microorganisms (Gram-positive and Gram-negative bacteria, antibiotic-resistant bacteria, and oocysts of C. parvum), and in the large-scale demonstration application. The results of this work suggest that MCNTs/RP/CN can serve as a high-performance and recyclable photocatalyst for real-world photocatalytic disinfection operations.