Hydrophobic carbon black-PTFE electrode for improved phenol mineralization in electro-peroxone with the synergy of O3/O2 reduction and catalytic ozonation

The mass transfer of O 2 /O 3 was improved at three-phase interface of CB‑PTFE. • CB enabled the synergistic reduction of O 2 /O 3 for •OH generation. • O 3 reduction and catalytic ozonation accelerated phenol mineralization. • Phenol removal and mineralization were 100% and 85% in ten-cycles. The electro-peroxone (E-peroxone) process suffered from the limited mass transfer and insufficient utilization of gaseous O 2 /O 3 mixture. Herein, a hydrophobic carbon black‑polytetrafluoroethylene (CB‑PTFE) electrode was fabricated to construct a gas‑liquid‑solid three-phase interface for improving phenol mineralization. The CB-PTFE electrode exhibited a high contact angle of 143.3°, which enhanced the mass transfer of O 2 /O 3 effectively. Compared with the hydrophilic carbon black‑polyvinylidene fluoride (CB‑PVDF) cathode (72.9°, 51.8%), CB‑PTFE achieved 86.0% TOC removal (0.016 min −1 ) at 120 min in E-peroxone, significantly outperforming sole ozonation (O 3 , 40.0%, 0.004 min −1 ) and electro‑oxidation (EO, 7.2%, 0.004 min −1 ). The greater TOC removal in CB-PTFE/O 3 (66.3%, 0.0095 min −1 ) than that in O 3 indicated that CB-PTFE had catalytic ozonation activity. Electrochemical analysis by a rotating ring‑disk electrode (RRDE) revealed that CB enabled simultaneous 2‑electron oxygen reduction reaction (ORR) to H 2 O 2 (n = 2.23) and efficient 1‑electron O 3 electro‑reduction for increased cathodic current and hydroxyl radical (•OH) generation under the O 2 /O 3 atmosphere. The highest •OH yield (280.5 μmol/L) was obtained using hydrophobic CB-PTFE in E‑peroxone, and theoptimal conditions were the applied current of 20 mA, in‑gas O 3 concentration of 50 mg/L and neutral pH of 7.0. Furthermore, the hydrophobic CB‑PTFE electrode maintained nearly 86.0% TOC removal over ten-cycles with stable structural integrity, despite a slight decrease of hydrophobicity. The reduction of O 2 /O 3 , catalytic ozonation and peroxone reaction were coupled in E-peroxone synergistically, which offered a promising strategy for efficient pollutant abatement. Download: Download high-res image (262KB) Download: Download full-size image