Photo-catalytic degradation of methyl orange and formaldehyde by Ag/InVO 4–TiO 2 thin films under visible-light irradiation

Abstract

Novel Ag/InVO 4–TiO 2 composite thin films were synthesized via a sol–gel method in order to elucidate their visible-light-driven photo-catalytic performance. A wide range of techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photo-electron spectroscopy (XPS), UV–vis absorption spectroscopy (UV–vis) and electron spin resonance (ESR) were applied to characterize the obtained composite thin films. The results revealed that the Ag/InVO 4–TiO 2 thin films extended the light absorption spectrum toward the visible region. Visible-light-induced photo-catalytic degradation of aqueous methyl orange (MO) and gaseous formaldehyde over Ag and InVO 4 co-doped TiO 2 thin films was observed. CO 2 and SO 4 2− were detected in the products of formaldehyde and methyl orange, respectively, indicating that formaldehyde and methyl orange were mineralized over the Ag/InVO 4–TiO 2 films under visible light. The effects of doped noble metal Ag by acting as electron traps and InVO 4 as a narrow band gap sensitizer in the Ag/InVO 4–TiO 2 films were also discussed. This study may provide an approach to treatment of organic pollutants by using visible light.