Photochemical transformation of C3N4 under UV irradiation: Implications for environmental fate and photocatalytic activity

In this study, the photo-transformations of bulk C 3 N 4 (CN) and oxidized C 3 N 4 (OCN) under UV-irradiation were examined. Through NO 3 − release measurements, we found that the photo-transformation rate of OCN is higher than that of CN. Various characterization results revealed the structural and chemical properties changes of CN and OCN after photo-transformation. We proposed that under reactive oxygen species attack, CN and OCN were gradually broken into smaller fragments and finally mineralized into NO 3 -, CO 2 , and H 2 O through the circular reactions of deamination-hydroxylation-decarboxylation. Through the zeta potential measurements and sedimentation experiments, the influence of photo-transformation on the water stabilities of CN and OCN were assessed. The stability of CN in water increased while the water stability of OCN decreased after photo-transformation, implying that the changes to C 3 N 4 -based materials caused by photo-transformation may significantly impact their environmental behaviors. Moreover, the photocatalytic activities of the photo-transformed OCN and CN substantially decreased, indicating that the structural changes might be the main reason for their photocatalytic activity loss. These findings highlight the non-negligible influence of photo-transformation on the fate of C 3 N 4 in aquatic environments, as well as on the photochemical stability during its use.