Direct hydro-alcohol thermal synthesis of special core–shell structured Fe-doped titania microspheres with extended visible light response and enhanced photoactivity

Fe-doped titanium dioxide (TiO2) microspheres with special core–shell structure were prepared by a simple hydro-alcohol thermal method. The morphology and microstructural characteristics of Fe-doped titania microspheres with different Fe3+ doping concentrations were characterized by means of BET, TEM, SEM, XPS, UV–vis DRS, PLS and XRD. The Fe3+ doped TiO2 samples showed the best photocatalytic activity, which were much superior to P25 under both visible and ultraviolet light irradiations. The concentration of Fe3+ was found playing a key role in the photocatalytic degradation of phenol, moreover, 0.5 mol% Fe3+ doping was an optimal amount. The probable mechanism was proposed: it was presumed that doping Fe3+ ions into TiO2 structure may overlap the conduction band of TiO2 and the d orbital of Fe3+, which leads to the marked narrowing of the band gap and the extension of visible light response. Meanwhile, since the Fe3+/Fe2+ energy level was just lower than the conduction band of TiO2 while the Fe3+/Fe4+ energy level was slightly above the valence band of TiO2, the Fe3+ dopant can not only play as a temporary trapping sites of photo-induced electrons but can also act as shallow capturing sites of photo-induced holes, which will efficiently separate the photoexcited electrons and holes, prolong the lifetime and at last improve the photocatalytic activity. The superior activity of Fe3+–TiO2 photocatalysts can also be ascribed to the special core–shell structure with high surface area, mesoporous pore and well-crystallized anatase phase.