Mineralization of norfloxacin in a CoFe–LDH/CF cathode-based heterogeneous electro-fenton system: Preparation parameter optimization of the cathode and conversion mechanisms of H2O2 to ·OH

Abstract

• The H 2 O 2 conversion mechanisms in Heterogeneous electro-Fenton system were obtained. • The functional roles of CoFe–LDH/CF cathode for H 2 O 2 conversion were researched. • Optimal preparation temperature of CoFe–LDH/CF for NFXN removal was obtained. • Excellent mineralization of NFXN was observed at all pH values after 8 h treatment. • The active metal sites of ·OH generation were researched based on DFT calculations. This study demonstrates an efficient heterogeneous electro-Fenton system with a CoFe–layered double hydroxide/carbon felt (CoFe–LDH/CF) cathode for norfloxacin (NFXN) removal. Two-dimensional CoFe–LDH prepared at the optimal temperature of 90 °C could produce sufficient catalyst dosages and highly crystallized honeycomb hexagonal nanoplates, revealing extraordinary (at least 90%) mineralization of NFXN at all pH values after 480 min of treatment. The brilliant catalytic activity presented over ~ 97% for the mineralization of NFXN after 5 cycles experiments, indicating the good reusability of the prepared cathode. According to density functional theory (DFT) calculations, ·OH could be generated easily since the lower energy barriers were achievable for intermediates absorbed on Co atoms rather than those absorbed on Fe atoms, demonstrating that the activity trend remained Co > Fe on CoFe–LDH. In addition, the mechanisms of H 2 O 2 generation on practical CoFe–LDH/CF cathodes were explored. The CF in the CoFe–LDH/CF cathode is a highly active and stable 2-electron ORR catalyst for H 2 O 2 production, which provides sufficient substrates for ·OH generation. This study potentially provides new insight into exploring the nature of reactions in hetero-EF systems.