Carbon quantum dots can enable efficient photochemical interfacial activation of molecular oxygen in iron oxides/oxalate system

Abstract

Photochemical reactions between natural iron oxides and oxalic acid (OA) have attracted wide attentions in environmental decontamination, but the critical interfacial ligand-to-metal charge transfer process (LMCT) is difficult to occur. In this study, carbon quantum dots modified maghemite (γ-Fe2O3/CQDs) with excellent photo-electrochemical properties has been successfully synthesized, which achieved rapid decomposition of sulfamethoxazole (SMX) with OA under UV. It was found that the complexed [≡FeIII(C2O4)n]3-2n on the γ-Fe2O3 surface could occur efficient interfacial LMCT, followed by fast internal transmission of electrons to CQDs part for activating its surface adsorbed O2 to efficiently produce O2•− and •OH. The heterogeneous LMCT would be dominant in UV/γ-Fe2O3/CQDs/OA system for the initial rapid SMX degradation, despite the non-reductive leaching of aqueous FeIII(C2O4)n3-2n would cause additional homogeneous LMCT. Bonded CQDs at iron oxides could highly improve utilization of the photo-generated electrons from complexed OA for O2 activation, and also broaden its application under visible light.