Synergistic effect on the four-electron ORR of the electro-Fenton system to remove micropollutants using an MOF-derived catalyst with carbon black

Highlights: • The pristine morphology of MIL(Fe) was maintained after thermal treatment. • The 310T sample introduced oxygen vacancies, singlet oxygen and hydroxyl groups. • CB with a 4e⁻ORR tendency exhibited an increased H₂O₂ yield. • The EF process with the 310T/CB@NF GDE combined 4e⁻ORR and Fenton-like reactions. The electro-Fenton (EF) process combines an oxygen reduction reaction (ORR) and Fenton-like reaction for application in water treatment. However, many electrode designs simply aim at H₂O₂ production or catalyze either the ORR or Fenton-like reaction. This paper explored the effect of pyrolysis on MIL-101(Fe) and found that a thermal treatment at 310 °C (310T) partly maintained the original crystal structure but exposed more Fe sites and oxygen vacancies (OVs). The fabricated 310T/CB@NF gas diffusion electrode had a 4e-ORR tendency, although it exhibited good performance even at low voltages (1.2 V) with the detected current below 10 mA. In the assessment of the H₂O₂ production, ability as a Fenton reagent and DCF removal, the EF process exhibited a synergy between 310T and carbon black (CB). 310T manifested good Fenton activity on the Fe sites and OVs and directly worked toward the DCF degradation. CB with a high ORR catalytic activity provided a basis for the high H₂O₂ yield, which is indirectly conducive to the DCF removal.