Atomic structure evolution of graphene prepared by hydrothermal method
In this study,the microstructural evolution of reduced graphene oxide to graphene was investigated by spherical aberration-corrected TEM.The removal effect of oxygen-contained functional groups during the reduction process was verified by XPS and FTIR.The high-resolution structure of graphene oxide was highly inhomogeneous.The contrast between graphitic regions and disordered regions was obvious.Oxygen atoms introduced by oxidation process combined with carbon atoms and destroyed C-C bond structures to form sp3 hybridized bonds,making monolayer graphene oxide partly disordered.The C/O ratio in graphene oxide is 1.7.The C/O ratio in hydrothermally reduced graphene is increased to 11.7,proving that the reduction process removed many oxygenic functional groups.At a low magnification,graphene showed a light and thin lamella with large lateral dimensions and different degrees of surface folds.Spherical aberration-corrected TEM image showed that graphene had a nearly perfect honeycomb structure at atomic scale with few defects presented in the reduced graphene sample.The deoxygenation process restored most π-conjugated bonds and sp2 hybrid structure of carbon atoms,and the reduction effect was obvious.This study further demonstrated that spherical aberration-corrected transmission electron microscopy was an important method for material characterization.The combination of diffraction and imaging mode can broaden the atomic structure analysis of nanomaterials.
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