Enhanced electron transfer and hydrogen peroxide activation capacity with N, P-codoped carbon encapsulated CeO2 in heterogeneous electro-Fenton process

Designing catalysts that can effectively activate oxygen and hydrogen peroxide is a huge challenge in electro-Fenton (EF) process. Considering the superior ability of electrons transport and activation of H2O2, ceria encapsulated with N, P-codoped carbon material was a promising catalyst for EF reaction. Herein, CeO2-NPCTX (where T and X represented the calcination temperature and the initial mass of CeO2, respectively) materials were synthesized via pyrolysis process and used as catalysts to degrade ciprofloxacin (CIP) in EF process. The results indicated that CeO2-NPC1000100 catalyst had good degradation performance under the optimal conditions. Compared with CeO2 and CeO2-NC1000100 catalysts, CeO2-NPC1000100 catalyst had more content of graphite N and more oxygen vacancies, which were beneficial to activation of oxygen and hydrogen peroxide. Scavenging experiments and electron paramagnetic resonance analysis confirmed ·O2- and ·OH were the main reactive oxygen species in the CIP degradation process. And three logical degradation routes of CIP were given. In addition, CeO2-NPC1000100 catalyst still had good stability after three times of continuous operation, and presented good universality for the treatment of a variety of antibiotic wastewaters. Finally, a convincing mechanism in the EF system with CeO2-NPC1000100 for CIP degradation was proposed.