A self-circulating cerium-rich CeO2-x/Bi2MoO6 heterojunction catalyst for boosting photo-Fenton degradation of fluoroquinolone antibiotics

Stoichiometric CeO2 as a Fenton-like cocatalyst generally suffers from low H2O2 activation efficiency and multitudinous metal leaching because of its sluggish circulation of Ce3+/Ce4+ redox couple. Herein, a cerium-rich non-stoichiometric CeO2-x cocatalyst was developed to accelerate the circulation of Ce3+/Ce4+, which greatly promoted the H2O2 activation and avoided the production of metal sludge. In this case, cerium-rich CeO2-x nanodots were perfectly anchored onto Bi2MoO6 nanosheets to fabricate a self-circulating CeO2-x/Bi2MoO6 (CEO/BIM) photo-Fenton system. Systematic studies showed that the optimized CEO/BIM-3 (the mole ratio of Ce to Bi was 0.75) sample manifested the highest photo-Fenton degradation rate (0.026 min−1) of ofloxacin (OX) only under 5 W white LED irradiation, which was 8.66 and 6.50 times that of individual Bi2MoO6 and CeO2-x, respectively. The enhanced performance was mainly attributed to the excellent and continuous circulation of Ce3+/Ce4+, which can greatly accelerate the H2O2 activation to produce more OH radicals. This study demonstrates the great potential of the self-circulating photo-Fenton system in degrading antibiotic pollutants and provides an alternative strategy for designing stable and efficient catalysts.