Enhanced degradation of tetracycline via Visible-light-assisted peroxymonosulfate activation over oxygen vacancy rich Fe2O3-CoFe2O4 heterostructures

Oxygen vacancy (OV) plays important role in photocatalysis as well as in peroxymonosulfate activation. In this work, OV rich Fe2O3-CoFe2O4 heterostructures were synthesized using a combustion method and tested for visible-light assisted PMS activation. With the presence of visible light, the Fe2O3-CoFe2O4/PMS/Vis system can efficiently degradation of tetracycline (TC) with removal rate of 98.1% within 20 min. While only 79.1% TC can be removed in the Fe2O3-CoFe2O4/PMS system without the presence of visible light. The SO4•- and O2•- are the main free radicals for TC degradation in Fe2O3-CoFe2O4/PMS/vis system, while SO4•- is the main free radical in Fe2O3-CoFe2O4/PMS system. Besides enhancing the TC degradation, the presence of visible light can also increase the reusability and stability of Fe2O3-CoFe2O4. The mechanism for the visible-light-assisted PMS activation over Fe2O3-CoFe2O4 was proposed based on systematically characterization of the photoelectronic properties of Fe2O3-CoFe2O4 and analyzing the ROS formed during reaction. The results also revealed that the presence of visible light could help to keep the concentration of OV in Fe2O3-CoFe2O4, which is vital for maintain the catalytic performance of the Fe2O3-CoFe2O4 catalyst. Therefore, we propose that the presence of visible light can replenish the OV of Fe2O3-CoFe2O4 catalyst consumed by PMS activation in time. This work provides a new insight into the role of OV in metal oxides/PMS/vis system, which is beneficial to design better photocatalyst for photo-assisted PMS activation.