Ultrafast piezo-photocatalytic degradation of organic pollutions by Ag2O/tetrapod-ZnO nanostructures under ultrasonic/UV exposure

Abstract

Ultrafast degradation of organic pollutions has been realized by the piezo-photocatalytic activity of Ag₂O/tetrapod-ZnO nanostructures under ultrasonic/UV exposure. Tetrapod-ZnO (T-ZnO) nanostructures are synthesized in mass production by a thermal evaporation method, and Ag₂O nanoparticles are uniformly loaded on the whole surface of T-ZnO nanostructures. Under both ultrasonic and UV exposure, Ag₂O/T-ZnO nanostructures can efficiently co-use the mechanical and UV energy to degrade organic pollutions, and the degradation speed is extraordinarily fast. Taking methylene blue (MB) as an example, Ag₂O/T-ZnO nanostructures (2 g L⁻¹) can completely degrade an MB aqueous solution (5 mg L⁻¹) within ∼2 min under ultrasonic (200 W) and UV (50 W) exposure. Such a degradation rate is much higher than previous results, and has potential applications in sewage treating techniques at the industrial level. In this process, the piezoelectric field of T-ZnO nanostructures and the build-in electric field of Ag₂O/T-ZnO heterojunctions can separate the photogenerated electron–hole pairs, lowering the recombination rate and enhancing the photocatalytic activity. The present results can promote the development of sewage treating techniques for environmental improvement.