Enhanced photocatalytic performance of TiO2 particles via effect of anatase–rutile ratio

• Comprehensive investigation on anatase–rutile phase transformation.
• Phase composition ratio can be controlled through annealing temperature.
• The effect of annealing temperature on physical and chemical properties were intensively investigated.
• The photocatalysis efficiency of TiO2 particles were evaluated.
• The results indicated the advantages of mixed phase anatase–rutile on photocatalysis mechanism.

In the present work anatase–rutile transformation temperature and its effect on physical/chemical properties as well as photocatalytic activity of TiO2 particles were investigated. The characterisation of the synthesised and annealed TiO2 particles were determined by X-Ray Powder Diffraction (XRD), scanning electron microscope (SEM), dynamic light scattering (DLS) and Brunauer–Emmett–Teller surface area analysis (BET). The refraction in the ultraviolet–visible (UV–vis) range was assessed using a dual-beam spectrophotometer. The photocatalytic performance of the particles was tested on methylene blue solution. The XRD data indicated that the percentage of rutile increased with the annealing temperature and almost 100% of anatase transformed to rutile at 1000 °C. In addition, the phase transformation was a linear function of annealing temperature so phase composition of TiO2 can be controlled by changing the annealing temperature. The SEM and BET results presented the increase of agglomerate size and the decrease of specific surface area with the increasing annealing temperature. This proved that anatase has smaller particle size and higher surface area than rutile. The photocatalytic activity of the annealed TiO2 powders reduced with the increase of annealing temperature. The samples annealed at 900 °C and 925 °C with anatase: rutile ratio of 92:8 and 77:23, respectively, showed the best activity. These results suggested that the photocatalytic activity of TiO2 particles is a function of phase composition. Thus it can be enhanced by changing its phase composition which can be controlled by annealing temperature.