Photocatalytic activity of ZnO nanoparticles with optimization of defects

- Pristine and air quenched ZnO nanoparticles were synthesized by simple combustion method.
- Synthesized ZnO for air quenched ZnO has better optoelectronic properties.
- ZnO nanoparticles for air quenched ZnO exhibiting complete photodegradation of Methyl Orange dye under UV irradiation.
- Photocatalytic activities for all the samples were observed in 150 min.

Tuning of defect levels is the major concern for the application of ZnO nanoparticles. These nanoparticles with different defect concentration were prepared by simple combustion method at 700 °C and subsequent quenching in air. The catalyst was characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), UV-vis spectroscopy measurements. XRD reveals that the cell volume increased with large temperature difference between 700 °C and quenched media. FTIR confirmed that the vibrational frequencies shifted from 519 cm−1 to 535 cm−1 point out the role of quenching defects. FESEM shows the size is of the order of 20-45 nm and found irregular distribution of grain boundaries in the quenched induced defects. Different morphology plays a major role in the enhancement of photocatalytic efficiency of synthesized nanoparticles. PL intensity indicates more oxygen vacancies for air quenched ZnO whereas; DTA study demonstrates that the synthesized ZnO is thermally stable. Kinetics study confirmed the photodegradation of methyl orange (MO) dye using this photocatalyst follows first order rate constant. It exhibits the complete degradation of dye only in 150 min under UV irradiation. Kinetic study revealed the rate constant of nanoparticles is 0.0165 min−1. Air quenched sample showed the higher intensity of defect band as compared to pristine ZnO.

Systematic scheme for photocatalytic activity.Pristine and air quenched ZnO nanoparticles were effectively synthesized by simple combustion method and effectively used as photocatalyst for photodegradtion of methyl orange dye. It was observed that air quenched ZnO nanoparticles shows the better properties as compared to pristine ZnO. The complete degradation of dye was observed in 150 min.94