In situ tuning of graphene oxide morphology by electrochemical exfoliation

This paper illustrates the electrochemical exfoliation of graphite for the synthesis of graphene oxide (GO) with few layers. Innovative design and arrangement of electrodes were adopted, which allowed simultaneous exfoliation and re-exfoliation of graphite anode. Electrolyte having different molar concentrations of an aqueous solution of sulfuric acid (H 2 SO 4 ) and pH offered successful exfoliation of graphite anode with a varying yield of GO. The addition of sodium hydroxide (NaOH) in the solution affected the exfoliation rate and the morphology of the GO sheets. The transition of GO sheets from clumping–scrolling–flat sheet edge rolling to nanoribbons was observed by the change of composition and pH of the electrolyte. GO sheets showed lateral dimensions ranging from 500 nm to 24 μm, and ribbons and scrolls were found to have dimensions up to 50 μm. With the help of transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, a mechanism of exfoliation has been proposed. In situ functionalization of graphene helped in imparting stability to the GO in solvents such as ethanol and water for more than 11 months. This study elaborates on the significance of solvated sulfate ions and provides a window of sulfate and hydroxyl ion combination for tuning of structural morphologies of GO. Graphical abstract