Modulating reactive oxygen species in O, S co-doped C3N4 to enhance photocatalytic degradation of microplastics

Abstract

Photocatalytic microplastic (MP) degradation via reactive oxygen species (ROS) is a considered environmentally friendly and sustainable approach for eliminating MP pollution in aquatic environments. However, it faces challenges due to the low migration and rapid recombination efficiency of charge carriers in photocatalysts. Herein, oxygen and sulfur co-doped carbon nitride (OSCN) nanosheets were synthesized through thermal polymerization coupled with a thermosolvent process. The O and S co-doping can reduce the bandgap and improve the light response of carbon nitride (C₃N₄). Meanwhile, O/S dopants effectively improve the delocalization of electron distribution, leading to increased carrier separation capacity, thereby promoting the formation of ROS and enhancing photocatalytic performance. Compared to C₃N₄, OSCN demonstrated significantly higher photocatalytic degradation and mineralization rates for MPs, including polyethylene (PE, traditional petroleum-based MPs) and polylactic acid (PLA, biodegradable bio-based MPs). Specifically, the mass loss of PE and PLA increased by 32.8 ​% and 34.1 ​%, respectively. Notably, ^•OH and ¹O₂ generated by OSCN synergistically catalyzed the degradation of PE, while ^•OH was the primary radical triggering the photolysis and hydrolysis of PLA. This study holds significant implications for the application of photocatalysis technology in the remediation of MP pollution in aquatic environments.