Formation of the Ti4O7 phase through interaction between coated carbon and TiO2

Fine particles of photocatalytic anatase TiO2 prepared through hydrolysis of titanium tetraisopropoxide were coated by carbon. A reduced phase, Ti4O7 was formed through interaction between TiO2 and the coating carbon. EXAFS analysis on this Ti4O7 phase showed an intermediate Ti-Ti distance between those in anatase and rutile, which agreed with the structure composed of two-dimensional slabs of Ti-O octahedra separated by a shear plane. This carbon-coated Ti4O7 was confirmed to have photocatalytic activity, even though a little lower than anatase, examining the decomposition of methylene blue in water under UV irradiation.