Enhancing photocatalytic performance of iron-doped TiO2 nanoparticles: Effects of annealing temperature on anatase-rutile mixed phase structure

Abstract

The photocatalytic activity of the methylene blue in metal oxide anatase-rutile mixed phase TiO2 nanoparticles doped with iron after annealing at various temperature has been investigated. The ratio Fe/Ti (wt 3 %) was prepared using the conventional co-precipitation technique with annealing treatment. X-ray Diffraction (XRD) analysis showed anatase (∼25 %) and rutile (∼75 %) phase structures, and the crystallite size increased with increasing temperature. The Fourier transform infrared (FTIR) transmittance band at 517 cm−1 for TiO2 stretching vibration mode was examined using Kramer-Kronig relation for determining the optical characteristic such as the refractive index (n), the extinction coefficient (k), the dielectric function, and the energy loss function. Further analysis of the optical properties of Fe-doped TiO2 NPs shows the Δ (LO−TO) is shrinker after annealing above 200oC that indicated more stable bonding. The field emission scanning electron microscopy (FESEM) micrographs show agglomerations formed into clusters like as edelweiss flowers and roses on the surface. UV–Vis measurement reveals that the optical energy gap decreased from 3.05 eV annealed at 200oC to 2.88 eV annealed at 500oC. The UV–Vis absorbance with varying the time from 30 to 120 min to MB as a pollutant is reduced as time irradiation increases with photocatalytic rates for annealing at 500oC is 0.0071/min. The predominant anatase phase alignment, stable bonding, and unique surface make iron doped TiO2 NPs a promising catalyst.