Thioacetamide and thiourea impact on visible light activity of TiO2

Visible-light activated titanium dioxide photocatalysts were prepared by hydrolysis of titanium (IV) isopropoxide with thioacetamide or thiourea, followed by calcinations at 450 degrees C. The experiments demonstrated that phenol and 4-chlorophenol in aqueous solutions were successfully degraded under visible light (lambda > 400 nm) using doped TiO2. The major effort was aimed at evaluation of the effect of thioacetamide and thiourea amount (from 0.5 to 5 wt%) used during synthesis on the photodegradation efficiency. It was found that thioacetamide and thiourea dosage of 5% in doped TiO2 resulted in the most pronounced photocatalytic activity - phenol was photooxided in 93 and 97% within 60 min, respectively. Gradual loss of photoactivity was observed due to ageing of modified TiO2 - even 70% after six months of storage. The catalyst powder was characterized by X-ray diffraction (XRD), X-ray photoelectron emission spectroscopy (XPS) and UV-vis absorption measurements. For TiO2 modified with thiourea, light absorption in the visible region gradually increased with the increasing dopant content. (C) 2007 Elsevier B.V. All rights reserved.