UV and Visible Light-Driven Production of Hydroxyl Radicals by Reduced Forms of N, F, and P Codoped Titanium Dioxide.

The photocatalytic activities of reduced titanium dioxide (TiO) materials have been investigated by measuring their ability to produce hydroxyl radicals under UV and visible light irradiation. Degussa P25 TiO was doped with nitrogen (N), fluorine (F), and/or phosphorus (P) and then subjected to surface modification employing a thermo-physicochemical process in the presence of reducing agent sodium borohydride (NaBH). The reduced TiO materials were characterized by a number of X-ray, spectroscopic and imaging methods. Surface doping of TiO was employed to modulate the band gap energies into the visible wavelength region for better overlap with the solar spectrum. Hydroxyl radical generation, central to TiO photocatalytic water purification applications, was quantitated using coumarin as a trap under UV and visible light irradiation of the reduced TiO materials. At 350 nm irradiation, the yield of hydroxyl radicals generated by the reduced forms of TiO was nearly 90% of hydroxyl radicals generated by the Degussa P25 TiO. Hydroxyl radical generation by these reduced forms of TiO was also observed under visible light irradiation (419 and 450 nm). These results demonstrated that simple surface modification of doped TiO can lead to visible light activity, which is important for more economical solar-driven applications of TiO photocatalysis.