Niobium oxide (Nb2O5) nanofibers have been synthesized by sol-gel based electrospinning technique. Pure hexagonal phase (H-Nb2O5) and orthorhombic phase (O-Nb2O5) nanofibers were obtained by thermally annealing the electrospun Nb2O5/polyvinylpyrrolidone composite fibers in air at 500 degrees C and 700 degrees C, respectively. The fibers were characterized using the X-ray diffraction, scanning electron microscopy, specific surface area analyzer and UV-vis diffuse reflectance spectroscopy. Photocatalytic activities of the obtained nanofibers were evaluated depending on the degradation of methyl orange. The results indicate that the heat-treatment temperature, the crystalline structure and the morphology affected the physical and chemical properties of the as-prepared Nb2O5 nanofibers. The H-Nb2O5 nanofibers obtained at lower temperature showed better potential for the application as a promising photocatalyst. (C) 2012 Elsevier Ltd. All rights reserved.