Nitrogen-Doped Titanium(IV) Oxide Particles as a Visible-Light-Responsive Photocatalyst Prepared from Exfoliated Titanate Nanosheets

抄録

Nitrogen-doped titanium(IV) oxide (NT) particles were synthesized from titanate nanosheets prepared by exfoliation of lepidocrocite-like layered titanic acid using tetrabuthylammonium hydroxide. The layered composites of nanosheets with ammonium ions intercalated in the interlayer spaces, which were prepared by treatment of the nanosheets with a solution containing ammonium ion at room temperature, were transformed to anatase crystallites of titanium(IV) oxide (TiO2) by calcination in air at 723 K. The powders exhibited a yellow color corresponding to photoabsorption in the visible region (400-500 nm) presumably due to generation of a localized dopant level within the band gap. Incorporation of nitrogen anion species was confirmed by N 1s X-ray photoelectron spectroscopy. In the case of visible light irradiation (400 nm and higher), the NT particles showed photocatalytic activity for oxidative decomposition of acetic acid in the presence of iodate anion (IO3-) as an electron acceptor, while a commercial TiO2 showed no photocatalytic activity under similar photoirradiation conditions. The fact that the photocatalytic reaction occurred negligibly over NT particles in the absence of IO3- indicates that IO3- acts as an electron acceptor in the visible-light-induced photocatalytic reaction and retards recombination of photo generated carriers in the NT particles.