Boosting activation of molecular oxygen on the surface of fluorine doped g-C3N4 for efficient degradation of tetracycline: Synergistic effect of surface double central atom coordination and photo-Fenton oxidation

Abstract

Largely limited by the high dissociation energy of the O-O bond, how to effectively promote the activation of molecular oxygen (O2) on the surface of the graphitic carbon nitride (g-C3N4) has always been the key to improving the photocatalytic performance of g-C3N4. In this study, by utilizing the coordination reaction between F-Fe and O-Fe, a complex (ox-Fe-F-g-C3N4) with F and Fe as central atom, oxalate (ox) and g-C3N4 as ligand molecule was successfully constructed. Relevant characterizations and density functional theory (DFT) calculations together verify that the electron transfer of complex was significantly promoted. It not only beneficial to enhance the ability of photogenerated holes (h+) to directly oxidize tetracycline (TC), but also helps to accelerate the activation of O2 to generate reactive oxygen species (ROS). In addition, under the action of photoelectron reduction, a photo-Fenton oxidation platform based on Fe (III) and Fe (II) cycling can be established on the surface of F-g-C3N4. This facilitates the conversion of H2O2 generated by activating O2 into hydroxyl radicals (•OH) with higher oxidative activity. Batch degradation experiments confirmed that under the synergistic promotion of surface coordination and photo-Fenton oxidation, the photocatalytic efficiency of ox-Fe-F-g-C3N4 is nearly 4 times that of pristine g-C3N4.