Visible-light responsive carbon-anatase-hematite core-shell microspheres for methylene blue photodegradation

Core shell carbon-anatase-hematite (C@TiO2@alpha-Fe2O3) microspheres with sandwich-like structures were synthesized by an effective three-step approach. Specifically, using carbonaceous saccharide microspheres as template directs the sequential deposition of TiO2 layer by the modified Staff method and subsequent alpha-Fe2O5 layer via the impregnating-calcination process. The samples were characterized by SEM, TEM, XRD, and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity towards degradation of methylene blue aqueous solution under visible light irradiation was significantly improved, as compared to that of the TiO2 hollow microspheres and TiO2@alpha-Fe2O3 hollow microspheres counterparts. This enhancement in photoactivity is mainly attributed to two positive effects of the coupling TiO2 between the C core and alpha-Fe2O3 shell. Firstly, a matching heterostructure between TiO2 and alpha-Fe2O3 could dramatically improve the separation of photoinduced electron hole pairs. Secondly, C-core could enhance the absorption in the visible light region, serve as good adsorbent towards dye molecules, and provide a network to rapidly transfer the photoexcited electrons from the conduction band of TiO2 during the photocatalytic process. The study also provides a general and effective method in the fabrication of core shell composites with sound heterojunctions that may show a variety of applications. (C) 2014 Elsevier Ltd. All rights reserved.