Photodegradtion of Methyl Orange in the Water on Undoped and Fe-doped TiO2 Nanotubes

Undoped and Fe-doped TiO2 nanotubes were fabricated by hydrothermally treating the solgel- derived undoped and Fe-doped TiO2 nanoparticles in a KOH aqueous solution. The light absorption edge the nanotubes extended to visible light region of ~449 nm at a maximal Fe molar content (3.86 %). Correspondingly, the optical bandgap narrowed to ~2.76 eV. The sunlight-excited degradation rate of methyl orange aqueous solution on the nanotubes increased as increasing Fe-doping content and initial solution pH. The photodegradation followed pseudo-first order reaction kinetics. The pseudo-kinetic rate constant increased from 0.133 to 0.513 h-1 as the increase of Fe content and initial pH. A maximal value was achieved at Fe molar content of 3.86 % and initial solution pH=9. The measurement of oxidation-reduction potential revealed a dominant reductive photocatalytic behavior of the nanotubes. The mechanism of enhancing photocatalysis of TiO2 nanotubes by Fe-doping was proposed.