Fabrication of ZnO/Au@Cu2O heterojunction towards deeply oxidative photodegradation of organic dyes

Abstract

Fabrication of heterojunction is an effective way of improving the photocatalytic performance of semiconductor in the photocatalytic wastewater treatment. ZnO/Au@Cu2O heterojunctions were successfully synthesised using Au nanoparticles loaded onto the surface of ZnO nanorods as heterostructural seeds to induce in situ growth of Cu2O shells. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, electrochemical workstation and UV–vis diffuse reflection spectrograph were employed to analyze the structures, compositions and photoelectric properties of the synthesised photocatalysts. After 45–90 min of the photocatalysis of ZnO/Au@Cu2O heterojunctions under simulated sunlight, the degradation efficiencies of methyl orange and rhodamine B could reach 93.0% and 99.6%, respectively, which were much higher than those with mono- and bi-component catalysts. The photocatalytic system with ZnO/Au@Cu2O can achieve deep mineralization to decompose organic dye molecules into non-toxic products. The formation of heterostructures not only could expand the spectral absorption range to the visible region but also efficiently facilitate charge separation to transfer more photo-generated holes and electrons to generate oxidative hydroxyl and superoxide radicals. A Z-scheme charge separation mechanism was proposed according to the determination of radical species and energy band structures of ZnO–Cu2O.