Photocatalytic degradation of organic compounds by Au-TiO2/sepiolite composites as the highly efficient catalysts

Abstract

Photocatalytic oxidation of methyl orange (MO) and Congo red (CR) as typical model organic contaminants was investigated in aqueous solution within a cooperating Au/TiO2/sepiolite heterostructure system under UV light irradiation. The Au/TiO2/sepiolite composites with a single-crystalline (anatase) framework was synthesized by a facile sol-gel method using titanium tetrachloride as a TiO2 precursor and depositing metal Au on the surface of TiO2 nanostructures via a facile chemical reduction process. The crystal structure, surface area, light adsorption and the photoinduced charge separation rate of the photocatalyst prepared were characterized in detail. As compared with the pristine TiO2, the Au/TiO2/sepiolite hybrid material exhibited good photocatalytic efficiency (90%) for the UV-light photooxidation of methyl orange, which is four-fold of that of reference TiO2. In addition, Au/TiO2/sepiolite hybrid material also shows a good photodegradation performance toward Congo red removal. The highly efficient photocatalytic activity is associated with the strong adsorption ability of sepiolite for aromatic dye molecules, fast photogenerated charge separation due to the formation of Schottky junction between TiO2 and metallic Au. This work suggests that the combination of the excellent adsorption properties of sepiolite and the efficient separation effect of noble metallic nanoparticles provides a versatile strategy for the synthesis of novel and highly efficient photocatalysts.