Self-assembled ZnO-rGO nanocomposite, a solid-state transformation to control its crystallite size

Abstract Nano-structured ZnO and reduced graphene oxide composites (ZnO-rGO) were self-assemble obtained via hydrothermal process. The composites were synthetized under hydrothermal conditions, using different amounts of a binder agent, in order to control the anchorage between the precursors (e-Zn(OH)2 and graphene oxide). Afterwards, a heating treatment was performed to induce the self-assembly of phases. Results indicates that a few layer graphene oxide was obtained with an average thickness of 6 sheets. X-Ray diffraction and Rietveld analysis revealed that it is possible to obtain ZnO nanoparticles with crystallite size of around 15 nm, while the thermogravimetric analysis showed ~ 70 wt. % of ZnO. The characterization by scanning-transmission electronic microscopy evinced that the ZnO nanoparticles were well distributed and anchored between and over the rGO sheets, forming at the same time a microporous structures with surface areas up to 78 m2/g. Therefore, the control of crystallite size of ZnO particles in the composite material was successfully carried out, promoting a good interaction between the metal oxide and the rGO sheets. Finally, electrochemical impedance spectroscopy evaluation was performed, and the results confirmed the codependency between the structural and physicochemical characteristics with the electrical conductivity. Hence, the formed materials are expected to have high capacity and stability if used as electrode of lithium-ion batteries.