Hydrothermal synthesis, characterization and enhanced photocatalytic performance of ZnO toward degradation of organic azo dye

The hexagon-like ZnO microstructure has been prepared at low temperature via hydrothermal method without using any surfactant, organic solvent or capping agent. ZnO belongs to hexagonal wurtzite structure. The formation of hexagon-like microstructure, with the grain size of about 480x720 nm (from SEM), is possibly due to assembling of many crystallites (crystallite size of 45-51 nm, from XRD). The blue emission over 420-500 nm may originate from the radiative combination due to surface defect states. ZnO showed high photodegradation efficiency of 95% after 80 min. The photodegradation reaction follows the pseudo first-order kinetics. ZnO photocatalyst retains its original efficiency (98%) even after the third cycle of reuse indicating the advantages of stability and reusability.