Boosting Hydroxyl Radical Yield via Synergistic Activation of Electrogenerated HOCl/H 2 O 2 in Electro-Fenton-like Degradation of Contaminants under Chloride Conditions

Hydroxyl radical production via catalytic activation of HOCl is a new type of Fenton-like process. However, metal–chlorocomplex formation under high chloride conditions could deactivate the catalyst and reduce the process efficiency. Herein, in situ electrogenerated HOCl was activated to • OH via a metal-free, B/N-codoped carbon nanofiber cathode for the first time to degrade contaminant under high chloride condition. The results show 98% degradation of rhodamine B (RhB) within 120 min ( k = 0.036 min –1 ) under sulfate conditions, while complete degradation ( k = 0.188 min –1 ) was obtained in only 30 min under chloride conditions. An enhanced degradation mechanism consists of an Adsorb & Shuttle process, wherein adsorption concentrates the pollutants at the cathode surface and they are subsequently oxidized by the large amount of • OH produced via activation of HOCl and H 2 O 2 at the cathode. Density functional theory calculations verify the pyridinic N as the active site for the activation of HOCl and H 2 O 2 . The process efficiency was also evaluated by treating tetracycline and bisphenol A as well as high chloride-containing real secondary effluents from a pesticide manufacturing plant. High yields of • OH and HOCl allow continuous regeneration of the cathode for several cycles, limiting its fast deactivation, which is promising for real application.