Key role of carbon as an efficient electron bridge in CuO@C@Fe2O3 for enhancing H2O2 activation during photo-assisted Fenton-like reaction

The Fe 3+ /Fe 2+ cycle has been identified as the rate-limiting step in the Fenton system, and many efforts have been made to promote the Fe 3+ reduction via external electrons provided by various electron donors. However, how to design an efficient electron transport pathway and then inhibit the invalid electron shuttle has been largely underestimated. In this study, two kinds of heterogeneous Fenton catalysts of CuO@Fe 2 O 3 and CuO@C@Fe 2 O 3 were prepared. The key role of carbon in transporting electrons as an electron bridge and its enhancement mechanism in photo-assisted Fenton-like performances were explored in detail. Compared with CuO@Fe 2 O 3 , the removal efficiency of tetracycline (TC) and the corresponding pseudo-first order reaction rate constants over CuO@C@Fe 2 O 3 increased significantly from 88.6 % and 0.1054 min −1 to 99.7 % and 0.2058 min −1 , respectively. Based on a series of probe experiments, visible light irradiation can promote the reduction of Cu 2+ to Cu + , then the carbon in CuO@C@Fe 2 O 3 can effectively transfer electrons from Cu + to Fe 3+ , enhancing the Fe 3+ /Fe 2+ cycle and the following Fenton-like efficiency. Since more ·OH while less ∙O 2 - was produced over CuO@C@Fe 2 O 3 , which further supports the fact that the enhanced Fe 3+ /Fe 2+ cycle was due to the transfer electron from Cu + to Fe 3+ instead of the Haber-Wiss mechanism. Hence, this study provides new insight for effectively improving the transfer efficiency and effective utilization of electrons in Fenton systems.