Structure and activity of iron-doped TiO2-anatase nanomaterials for gas-phase toluene photo-oxidation

The structural (from local to long range order) and electronic evolution of Fe-doped anatase nanomaterials is evaluated using in situ synchrotron based X-ray total scattering/diffraction and absorption techniques and Raman spectroscopy. These methods are combined with UV-visible spectroscopy and infrared diffuse reflectance (DRIFTS) to maximize the level of structural and morphological information regarding these materials. Fe doping of anatase nanomaterials generates solids having Fe at substitutional positions of the structure, and anion vacancies as charge neutrality entities. These structural modifications lead to materials with decreasing band gap energy as a function of Fe content. Concomitantly, mid-gap electronic states are observed to appear. At the same time, the presence of Fe alters the primary particle shape of the anatase without changing significantly the primary particle size. In contrast with previous results, analysis of the combined results strongly indicates that UV and visible photocatalytic activity are here dominated by morphological rather than structural/electronic issues.