Mesoporous Fe-doped TiO2 sub-microspheres with enhanced photocatalytic activity under visible light illumination

Mesoporous Fe-doped TiO2 sub-microspheres (m-Fe-TMS) with high surface area, accessibility, and crystallinity were prepared using a rapid and continuous aerosol-assisted self-assembly (AASA) process for visible-light photocatalytic degradation of persistent pharmaceuticals. The results of X-ray absorption near-edge structure (XANEX) spectroscopy indicate that iron exists as octahedrally coordinated Fe3+ ions substituting Ti4+ in the TiO2 lattice. The similarity of the Fe/Ti ratios in the bulk and on the surface, as determined by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), reveals that the substitution of Ti4+ by Fe3+ ions uniformly occurs within m-Fe-TMS. UV-vis diffuse reflectance spectroscopy shows that m-Fe-TMS exhibits a shift in the absorption threshold toward the visible spectrum. Under visible light irradiation, m-Fe-TMS exhibits a maximum rate of pharmaceutical photodegradation four times that of m-TMS. The photocatalytic degradation rates are reproducible with m-Fe-TMS, even after 10 repeated runs. The formation of chemical Fe-O-Ti bonds, and not of isolated Fe2O3 particles, leads to the inhibition of photocorrosion and leaching in the photocatalytic reactions. The ease and scalable production of m-Fe-TMS using the AASA process will facilitate the development of visible light-driven photocatalysts for decomposition of environmental contaminants. (C) 2012 Elsevier B.V. All rights reserved.