Exploring the photocatalytic activity of surfactant-free ZnO micro-flowers synthesized by microwave-assisted method

[Display omitted] •The rapid synthesis of zinc oxide by microwave-assisted method.•Formation of the highly crystalline and sharp-edged ZnO micro-flowers.•Dye degradation of highly concentrated Methylene Blue with 90% efficiency. In present study, surfactant-free synthesis of highly crystalline ZnO micro-flowers was carried out by using the microwave-assisted method with a 4 min reaction time. The effect of different microwave powers on crystal structure, morphology, and photocatalytic activity was studied. The ZnO synthesized at 450 W showed better physico-chemical and photocatalytic performance. XRD pattern showed the formation of the highly crystalline wurtzite/hexagonal crystal structure with an average crystallite size of 31 nm. The presence of Raman active bands validated the formation of wurtzite/hexagonal crystal structure of the ZnO. Moreover, the XPS analysis confirmed the presence of Zn and O elements while the highest specific area of 24.2 m2/g was observed from BET. The morphological studies showed the formation of the ZnO microflowers with an average size of 5 μm. Synthesized ZnO showed a band gap of 3.19 eV. To check the applicability, the photodegradation of methylene blue by ZnO micro-flowers was studied under solar light. For 450 W, due to the highly crystalline and sharp-edged microstructure, high photodegradation efficiency is obtained at about 90 % with recyclability of 72.8 % after 3 cycles. Based on the obtained results, a microwave with low power can be utilized to prepare highly crystalline microstructures of ZnO for better photocatalytic activity with very short reaction time.