Electrochemical fabrication and properties of highly ordered Fe-doped TiO 2 nanotubes

Abstract

Highly-ordered Fe-doped TiO 2 nanotubes (TiO 2nts) were fabricated by anodization of co-sputtered Ti-Fe thin films in a glycerol electrolyte containing NH 4F. The as-sputtered Ti-Fe thin films correspond to a solid solution of Ti and Fe according to X-ray diffraction. The Fe-doped TiO 2nts were studied in terms of composition, morphology and structure. The characterization included scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, UV/Vis spectroscopy, X-ray photoelectron spectroscopy and Mott-Schottky analysis. As a result of the Fe doping, an indirect bandgap of 3.0 eV was estimated using Tauc's plot, and this substantial red-shift extends its photoresponse to visible light. From the Mott-Schottky analysis, the flat-band potential (E fb) and the charge carrier concentration (N D) were determined to be -0.95 V vs Ag/AgCl and 5.0 ×10 19 cm -3 respectively for the Fe-doped TiO 2nts, whilst for the undoped TiO 2nts, E fb of -0.85 V vs Ag/AgCl and N D of 6.5×10 19 cm -3 were obtained. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.