Effect of Annealing Temperature on Structural Phase Transformations and Band Gap Reduction for Photocatalytic Activity of Mesopores TiO2 Nanocatalysts

Abstract

The titanium dioxide nanocatalyst (TiO2:NC) was fabricated by chemical precipitation method and annealed at different temperatures. The texture parameters was estimated by Barrett–Joyner–Halenda (BJH) and Brunauer–Emmett–Teller (BET) utilizing nitrogen adsorption–desorption data. The crystal phase transition, enhanced crystallinity and increase in crystallite sizes with temperature were studied by using X-ray diffractograms (XRD). Coinciding with an increase in crystallite size supervising annealing temperatures, the surface area of the TiO2:NC decreases. The average grain size as calculated from scanning electron microscopy (SEM) initially decreases with increasing annealing temperature (300 °C), whereas further increase in annealing temperature (600 °C), is accompanied by the increase in grain size. A red shift was observed in the diffuse reflectance spectra (DRS) caused by a decrease in band gap energy with rising annealing temperatures. The chemical composition was examined by using Fourier transform infrared (FTIR) and energy dispersive X-ray (EDX) spectroscopies. All the annealed TiO2:NC samples were used as photocatalysts for the degradation of rhodamine 6G (R6G) under simulated solar light source. The TiO2:NC annealed at 600 °C have a higher degradation rate constant than the other samples.