Progress and Perspectives in Visible-Light-Driven Photocatalysis

Abstract

The development of nanotechnology for the synthesis of nanomaterials is providing unprecedented opportunities to deal with emerging environmental problems associated with water and air contamination along with worldwide energyrelated concerns.Advanced oxidation technologies (AOTs) and nanotechnologies (AONs) have been extensively investigated for the destruction of toxic and recalcitrant organic compounds and inactivation of microorganisms in water and air.Photocatalysis as a part of AOTs is an effective method to completely decompose organic pollutants in air and aqueous solutions/natural waters.However, conventional wide band gap semiconducting materials (TiO 2 , ZnO, etc.) usually employed in photocatalytic processes absorb radiation below 400 nm, which is in the UV region, being only 5% of the solar light.In order to effectively utilize solar light as the source of energy, modified materials that can also absorb in the visible spectrum need to be synthesized.Recently, doping TiO 2 with different heteroatoms (metal and/or nonmetal ions) made it possible to shift the absorption towards longer wavelengths and, thus, allow TiO 2 sensitization in the visible region.Due to the visible light absorption abilities, doped TiO 2 -based powders and films can also be used for improving the photocatalytic process in the visible region.Several attempts have been directed towards the development of modified TiO 2 with visible light response by dye sensitization, metal (Fe, Co, Ag), and nonmetal (N, F, C, S) doping of the catalyst to reduce TiO 2 band gab energy