Nitrogen-doped TiO₂ fibers for visible-light-induced photocatalytic activities

Nitrogen-doped TiO₂ fibers (N–TiO₂ Fs) were successfully and efficiently fabricated using titanium diisopropoxide bis(acetylacetonate) and polyvinylpyrrolidone (PVP) as a carrier polymer and nitrogen source via centrifugal spinning and subsequent calcination methods. XRD analysis confirmed that N–TiO₂ Fs contains only anatase and rutile phases. XPS analysis revealed that N-atoms (from PVP) were successfully incorporated into the lattice of TiO₂ whereas DTA and FTIR analysis confirmed that calcination at 550 °C for 1 h is appropriate to remove all organic impurities from the N–TiO₂ Fs. SEM images showed that the N–TiO₂ Fs of diameter (0.65 μm–1.2 μm) were produced and controlled with the amount of Ti-precursor. BET analysis confirmed that the addition of commercial TiO₂ nanoparticles increased the specific surface area of the N–TiO₂ Fs. UV–Vis diffuse reflectance measurements showed that N–TiO₂ Fs exhibited a stronger light absorption in the visible region and a red-shift which is responsible for narrow band gap energy owing to the presence of N-atoms in the TiO₂ lattice. This results in enhanced photocatalytic activity of the synthesized N–TiO₂ Fs for degradation of methylene blue under visible light irradiation.