Singlet-Oxygen-Driven CeO 2 Quantum Dots/Hollow Spherical g-C 3 N 4 S-Scheme Heterojunction Photocatalyst for the Degradation of Tetracycline

Antibiotics in water have an important impact on human health, and the advanced oxidation process (AOP) is an environmentally friendly method to solve the problem of antibiotics in water. Still, research lacks the main active substances for photocatalytic degradation and their generation mechanism. In this article, cerium oxide quantum dots (CeO2-QDs)/hollow spherical carbon nitride (CNHS) photocatalysts were synthesized to evaluate the photocatalytic activity through the degradation of tetracycline (TC). Copula CeO2-QDs with CNHS to form S-scheme heterojunctions enhance photogenerated carrier migration and diffusion and broaden the photoresponsivity range. 5% CeO2-QDs/CNHS had the best photocatalytic performance and reached tetracycline degradation equilibrium within 10 min. The theoretical system of degrading TC with single oxygen (1O2) as the main active substance was also established, and it was confirmed that the combination of •O2– and H2O was the main pathway to produce 1O2 by this catalyst. A mechanism of TC degradation with 1O2 as the main active substance was proposed to provide a reference for constructing g-C3N4-based photocatalysts with efficient photodegradation activity.