Fabrication of Boron modified bi-functional air diffusion electrode for ciprofloxacin Degradation: In-situ H2O2 generation and self-activation

Abstract

In order to improve H₂O₂ in-situ generation in electrochemical system, a boron (B) modified air diffusion electrode (B@ADE) was fabricated in the present study. Carbon black (CB) doped by B was deposited on ADE surface as catalytic layer. Performance of B@ADE with different B/C mass ratios has been investigated and 0.3 was identified as the optimal one·H₂O₂ yield can be achieved 204.85 mg L^-1 within 45 min at 0.3-B@ADE, which was 1.51 times for that of ADE. Meanwhile, H₂O₂ self-activation on B@ADE surface was observed and effects of different operating parameters on ^•OH formation have been analyzed. XPS analyzation demonstrated that BC₂O, BC₂O and C = O/O-C = O were related to H₂O₂ generation. DFT calculation revealed that BCO₂ was benefit for O₂ adsorption, while BC₂O promoted *OOH desorption with lower free energy barriers for H₂O₂ and ^•OH generation. Quenching experiments for ciprofloxacin (CIP) demonstrated that ^•OH, O•-2 and ¹O₂ were co-existed in the system with their contribution quantified. Four possible degradation pathways were proposed through active sites identification by DFT calculation and intermediates detection by HPLC-MS/MS. Bio-toxicity analyzation results showed that the toxicity of most intermediates was lowered than CIP. These results proved that electrochemical oxidation system with B@ADE enhanced in-situ H₂O₂ generation and self-activation, with great potential for practical application.