Boosting photocatalytic ozonation activity through F or I doping in g-C3N4: A trade-off between stability and performance

g-C 3 N 4 (CN) based catalysts were effective for photocatalytic ozonation (PCO), but their stability during reaction remained a mystery. This study investigated the change on PCO activity and stability of CN induced by F or I doping. Compared with CN, F-CN had the greater VB potential while I-CN had a greater CB position, which both led to their better O 3 activation. F-CN and I-CN PCO showed the greater oxalic acid (OA) degradation than that of CN PCO process. Though the enhanced activity, both F-CN and I-CN demonstrated the lower stability compared with that of CN. Because of the existing of reactive oxygen species (ROS) like •OH, •O 2 - and h vb + , CN, F-CN and I-CN were partially oxidized, generating NO 3 - and organic molecules such as cyanuric acid. h vb + and •OH mainly accounted for the decomposition of three CN. Triazine ring oxidation resulted in internal tearing and edge fracture as well as the formation of O-containing groups on all CN-based catalysts. O contents in catalysts initially increased and then decreased with reaction time, indicating that surface O-containing groups were unstable. The structural destroy could be eased with the present of organic pollutants. This study deepened the understanding of fate of CN based catalysts during PCO application.