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 photo-absorption measurements were also found to be responsible for the enhanced photocatalytic activity of the as synthesized samples.

Graphical abstractThermal plasma synthesized nanophase zirconia showing the blue shift in the band gap of monoclinic phase as found from the photoabsorption spectroscopy was found to be the dominant parameter for the enhancement in its photocatalytic activity. The existence of different defect states and their concentration in as synthesized samples also inferred from the photoabsorption measurements were also found to be responsible for the enhanced photocatalytic activity of the samples.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Phase controlled structural formation of nanophase ZrO2 by thermal plasma route. ► Enhanced photocatalytic degradation rate of methylene blue dye. ► The blue shift in the band gap of monoclinic phase of nanocrystalline ZrO2. ► Existence of different defect states in the as synthesized nano phase ZrO2. ► Several competing processes which controls the photocatalytic degradation rate.