Effects of electronic structure and interfacial interaction between metal-quinoline complexes and TiO 2 on visible light photocatalytic activity of TiO 2

Two metal-quinoline complexes, Fe(III)-8-hydroxyquinoline-5-sulfonic acid (Fe-HQS) and Er(III)-8-hydroxyquinoline-5-sulfonic acid (Er-HQS), were used as sensitizers of TiO 2 for improving visible light photocatalytic activity of TiO 2 . UV-vis spectra, X-ray Diffraction, X-ray Photoelectron Spectroscopy, Scanning Electron Microscope and Transmission Electron Microscope were put to use to characterize the structure and morphology of Fe-HQS-TiO 2 and Er-HQS-TiO 2 . The effects of interfacial electron transfer and energy level matching between each complex and TiO 2 were researched intensively. Er-HQS-TiO 2 and Fe-HQS-TiO 2 exhibited enhanced photocatalytic activity on photodecomposition of phenol in aqueous solution under visible light irradiation comparing to that of pure TiO 2 . According to photoelectrochemical response property and theoretical calculation of energy levels, two possible energy matching modes and photoelectron transmission pathways were proposed to explain the effects of Fe-HQS and Er-HQS on the interfacial interaction between metal-HQS complex and TiO 2 , and their different photocatalytic activities under visible light irradiation. The work in this paper indicated that metal-HQS complex with appropriate electronic structure and HOMO-LUMO energy levels relative to the band gap of TiO 2 played a major role in improving TiO 2 photocatalytic activity