Influence of crystalline phase and defects in the ZrO2 nanoparticles synthesized by thermal plasma route on its photocatalytic properties

The photocatalytic activity of pure ZrO2 samples, prepared by a thermal plasma route, and characterized by X-ray diffraction technique was tested for the degradation of methylene blue, which is known to be a hazardous dye. Although, all these samples synthesized at different operating pressures of the thermal plasma reactor showed the photocatalytic activity; the sample synthesized at 1.33 bar of operating pressure showed the highest photocatalytic activity. The blue shift in the band gap of monoclinic phase, as observed from the photo-absorption spectroscopy, may be attributed to the enhanced photocatalytic activity. The existence of different defect states and their concentration as, inferred from the photoabsorption measurements were also found to be responsible for the enhanced photocatalytic activity of the as synthesized samples. (c) 2012 Elsevier Ltd. All rights reserved.