Electrocatalytic dechlorination of halogenated antibiotics via synergistic effect of chlorine-cobalt bond and atomic H*

Although noble metal electrocatalysts are highly efficient in the dehalogenation of halogenated antibiotics, the prohibitive cost hinders their practical applications. In this study, a cobalt-phosphorous/oxide (Co–P/O) composite prepared via a one-step electrodeposition was for the first time applied in electroreductive dechlorination of halogenated antibiotics (HA), including chloramphenicol (CAP), florfenicol (FLO) and thiamphenicol (TAP). Co–P/O had a higher FLO dechlorination efficiency (91%) than Pd/C (69.3%) (t = 60 min, C₀ = 20 mg L⁻¹, applied voltage of −1.2 V vs. saturated calomel electrode (SCE)). Furthermore, the dechlorination efficiencies of Co–P/O for CAP and TAP reached to 98.7 and 74.2%, respectively. The electron spin resonance and in situ Raman characterizations confirmed that atomic H* was produced via the Co–P and the formation of Co–Cl bonds occurred on the Co–O in Co–P/O. The Co–Cl bond formation could trap HA molecules onto Co–P/O and weaken the C–Cl bond strength. The synergistic effect of H* attack and Co–Cl bond was responsible for the high dechlorination efficiency. This study offers new insights into the interface mechanism of electroreductive dehalogenation process, and shows a great potential for the remediation of halogenated antibiotics contaminated wastewater.