One-pot hydrothermal preparation of capsule-like nanocomposites of C/Ce-co-doped ZnO supported on graphene to enhance photodegradation

Abstract

Capsule-like nanocomposites of C/Ce-co-doped ZnO (C/Ce–ZnO) deposited on graphene sheets (CCZG) were successfully synthesized by a one-pot hydrothermal method at 150 °C for 24 h to promote the photocatalytic degradation of methylene blue (MB) under visible light irradiation. The UV-vis spectra and photoluminescence spectra illustrated a band gap of 2.72 eV and a blue shift for CCZG as compared to ZnO or C/Ce–ZnO. The structural analysis confirmed the existence of interstitial sites on ZnO lattices due to the presence of dopants which directly narrowed the band gap of materials. To elucidate the photocatalytic performance, MB degradation experiments were performed under various conditions involving the graphene percentages in the as-prepared materials, the pH value of the reaction solutions, the initial MB concentration, and the irradiation sources. For every condition, CCZG exhibited a high degradation efficiency since most initial MB substances vanished after 60 to 90 min of light irradiation. In addition, a decrease of 6.45% in degradation efficiency after being recycled seven times indicated good durability and stability of CCZG. Furthermore, the degradation process, the charge transfer, and the roles of generated reactive reagents (electrons, holes, hydroxide, and peroxide radicals) were also proposed and discussed in detail.