In-situ ionothermal precipitation of well-dispersed ZnO nanoparticles onto 2-dimension neat graphene sheets with excellent photocatalytic activity

Abstract

Neat graphene (NG) is rarely selected as a support to improve the photocatalytic performance of metal oxides due to its extremely poor processability in aqueous solutions. In this study, an in-situ ionothermal precipitation was developed to fabricate ZnO nanoparticle and few-layered NG sheet nanohybrids (ZnO/NG) in one-pot. Choline chloride/diethylene glycol-based deep eutectic solvent was used as reaction medium to dissolve the zinc salt precursor and disperse graphene. XRD, Raman, XPS and TEM analyses showed that ZnO particles with sizes of 15–25 nm were uniformly dispersed on the graphene sheets and a bond of ZnOC was formed between the interfaces. The UV–vis diffuse reflectance spectra measurement exhibited that the incorporation of graphene slightly narrowed the bandgap of ZnO nanoparticles, but significantly enhanced the light absorption of the nanohybrids in the visible range. Photocatalytic degradation of methylene blue dye evidenced that ZnO/NG offered excellent photocatalytic performance, regardless of UV or visible light irradiation. Under UV light, graphene as an electron transporter effectively promoted the separation of photogenerated carriers, while under visible light graphene was sensitized from the ground-state to the excited-state. The resulting electrons were injected into the conduction band of ZnO to transform wide bandgap ZnO into a photocatalyst driven by visible light. This work provided a green and simple method to prepare ZnO/NG nanohybrids with efficient and stable photocatalytic performance for water pollution remediation.