Graphene oxide and reduced graphene oxide supported ZnO nanochips for removal of basic dyes from the industrial effluents

Abstract

Currently, graphene and its functional derivatives are in high demand due to their unprecedented potential to build multifunctional catalysts. Here, we report the synthesis of highly active and cheap photo-catalyst materials consisting of sol-gel synthesized ZnO nanochips, assembled over the oxidized (GO) and partially reduced (RGO) derivatives of graphene in presence of ultrasound radiations. Structure, crystallite size, morphology, optical and photo-catalytic properties of as synthesized ZnO nanochips, ZnO@GO, and ZnO@RGO nanocomposites were investigated. Results demonstrated that ZnO nanochips incorporated over graphene sheets showed higher photo-catalytic rates with ∼76.5–98.9% degradation of Rhodamine-B (RhB) and Methylene Blue (MB) within 90 min of visible light irradiation. Moreover, ZnO@RGO was more efficient photo-catalyst than ZnO@GO with ∼2.4 and ∼2 times higher kinetic rates for the removal of RhB and MB, respectively. The superior performance of ZnO@RGO was ascribed to partially restored conjugated structure of RGO that dispense higher charge density on surface of photo-catalyst per unit time, by more effective charge migration and separation across semiconductor-caron (S-C) heterojunctions. The active species involved in degradation process were systematically investigated and a photo-catalytic mechanism was proposed. In addition, ZnO@GO and ZnO@RGO showed good recyclability and resistance to photo-corrosion even after 360 minutes of consecutive photo-catalytic activity.

Keywords:

• Graphene
• ZnO nanochips
• ZnO@GO and ZnO@RGO composites
• heterojunction
• photo-degradation

Acknowledgement

Authors are thankful to the Islamia University of Bahawalpur (Pakistan) and Higher Education Commission of Pakistan. Authors from King Saud University, sincerely appreciate the Deanship of Scientific Research, King Saud University Riyadh (Saudi Arabia) for their contribution through Research Group No: 1438-068. Dr. Sonia Zulfiqar is grateful to American University in Cairo for STRC mini-grant and project SSE-CHEM-S.Z.-FY19-FY20-FY21-RG (1–19)-2018-Oct-01-17-53-22.