Copper impregnated ionic liquid assisted mesoporous titania: visible light photocatalyst

Abstract

Mesoporous titania (Ms-TiO₂) is successfully prepared using water immiscible room-temperature ionic liquid 1-butyl-3-methyl-imidazolium-tetrafluoroborate as a template and an effective additional solvent via the sol–gel method at low temperature. Ms-TiO₂ is designed as an efficient visible light photocatalyst by copper (Cu) impregnation. X-ray diffraction analysis presents the nanocrystalline anatase phase. Cu impregnated Ms-TiO₂ (Cu/Ms-TiO₂) samples extend the absorption edge to the visible region. The X-ray photoelectron spectrum indicates the mixed valence states of Cu as Cu⁺ and Cu²⁺. The beneficial effect of Cu can be explained by the formation of oxygen vacancies with more Cu⁺ state. Cu/Ms-TiO₂ samples exhibit superior visible light photocatalytic activities to Ms-TiO₂, P-25 and 2.0% Cu/P-25 in the case of 2,4-dichlorophenol and methyl orange. Efficient charge separation due to the formation of Ti–O–Cu bonding at the surface and the associated appearance of oxygen vacancies together form the reason for higher degradation rate of organic compounds under illumination.