Electro-reduction induced fast metal redox cycle on Co3O4-CuO@CNTs/Copper foam cathode for enhanced Fenton-like reaction.

In this study, free-standing Co3O4-CuO/CF electrodes are synthesized via an electrodeposition-annealing process and then protected by dip-coated carbon nanotubes (CNTs). The obtained Co3O4-CuO@CNTs/CF is employed as cathode to activate peroxymonosulfate (PMS) for the degradation of Bisphenol A (BPA) in an electrochemical system. The electrochemical assistant (EA) plays a critical role to accelerate metal redox by donating electrons sustainably, and the fast regeneration of Co2+/Cu+ could be achieved to promote chemical-catalysis for PMS activation, which is proved via the pre-electroreduction treatment. The rate constant of Co3O4-CuO@CNTs/CF/PMS system with EA is ∼ 4.4 times compared to the system without EA. It also exhibits an excellent stability, which could still remove over 90% of BPA after eight cycles in 45 min. In addition, the coating of CNTs could decrease leaching of metals effectively. According to quenching tests and electron spin-resonance spectroscopy (ESR), the presence of EA could enhance the radical route by producing more SO4•- and •OH greatly, which is also proved by much faster degradation of carbamazepine (CBZ) and atrazine (ATZ) than that without EA. This work reveals activation mechanism of PMS in the electrochemical system, and provides an effective strategy to achieve the fast metal redox cycle for effective and long-term pollutant degradation.