Mechanism insight into double S-scheme heterojunctions and atomic vacancies with tunable band structures for notably enhanced light-driven enrofloxacin decomposition

Building narrow band gap semiconductors and fast separation of photogenerated electron-hole (e - -h + ) structures are of great significance for photocatalytic process. In this contribution, the CeO 2-x /C 3-y N 4 /Ce(CO 3 )(OH) double S-scheme heterojunctions with atomic vacancies tunable band gap (2.54 eV) have been designed and fabricated as a boost photocatalyst for enrofloxacin (ENR) photodegradation. Compared with the control samples, the experimental results indicate that the typical sample (CeO 2-x /C 3-y N 4 /Ce(CO 3 )(OH)-2) achieves the highest ENR photodegradation efficiency (93.6 %) in 240 min under a pH of 6, and the possible photodegradation pathways are also proposed. The superior performance is ascribed to the CeO 2-x /C 3-y N 4 /Ce(CO 3 )(OH) double S-scheme heterojunctions for selective recombination of photogenerated electrons with weak-reduction ability in conduction band (CB) of CeO 2-x , C 3-y N 4 and the photogenerated holes with weak-oxidation nature in valance band (VB) of C 3-y N 4 , Ce(CO 3 )(OH), which increase the retention rate of photogenerated electrons in CB of Ce(CO 3 )(OH) and photogenerated holes in VB of CeO 2-x to degrade ENR. This is the first systematic study of CeO 2-x /C 3-y N 4 /Ce(CO 3 )(OH) double S-scheme heterojunctions for ENR photodegradation.