Photoelectrocatalytic generation of miscellaneous oxygen-based radicals towards cooperative degradation of multiple organic pollutants in water

In the present photoelectrochemical (PEC) system utilizing MoS2 nanoflakes as a wide spectrum absorptive photoanode, simultaneous PEC degradation of different organic pollutants was achieved by employing in situ generated oxysulfur radicals, superoxide and hydroxyl radicals as strong oxidants. In order to better understand the cooperative PEC degradation of representative organic pollutants including rhodamine B dye (RhB), chlorpyrifos (CPF) and ciprofloxacin (CIP), the influences by bias potential, solution pH, radical scavenger, dissolved oxygen concentration and electrolyte concentration have been investigated. The selective PEC degradation efficiency follows the order of CPF > RhB > CIP in mixed substrates condition. In addition, the degradation rate for the single substrate degradation was about two times higher compared to that in mixed substrates degradation. The experimental results verified that reactive oxidation species (ROS) including oxysulfur radicals, superoxide and hydroxyl radicals can be efficiently produced on both anode and cathode under visible light irradiation, and they work together for simultaneous degradation of different pollutants, but the contribution of each ROS for pollutant degradation is substrate dependent. These results indicate that cooperative oxidation of multiple pollutants by miscellaneous oxygen-based radicals should be further considered as a promising advanced oxidation technique.