Electronic and atomic structure of TiO2 anatase spines on sea-urchin-like microspheres by X-ray absorption spectroscopy

Abstract Titania mesoporous sea-urchin-like microspheres were successfully synthesized by two-step template-free hydrothermal method. The sea-urchin-like microspheres have TiO2 anatase phase spines. The size and shape remain unchanged with amorphous TiO2 in all the microsphere samples. Controlling the spines quantity of sea-urchin-like microspheres with different concentrations of NaBH4 precursor are expected to improve the photocatalytic ability. The 0.8 wt% NaBH4 precursor showed the highest photocatalytic activity in the degradation of acetaminophen. X-ray absorption spectroscopy results indicated that the surface spines have an anatase phase structure, slight lattice distortion as well as a variation in Ti 3d orbital orientation. The microspheres with different NaBH4 precursor concentration have a significant effect in the electronic structure and showed a strong correlation to the oxygen defect in the spines and local structural symmetry of TiO6 octahedra (Oh). More detailed spectral analysis in the unoccupied states above the Fermi level strongly points to a photon degradation. Since Ti3+ strongly influences the surface chemistry of anatase phase, the structure along with the oxygen defect and the Ti3+ ions in the spines are considered to have an essential role in the photocatalytic process of TiO2 for the photogenerated electrons and an indication of an increase in the photocatalytic activity.