Structural Modulation of Exfoliated Graphene via a Facile Postultrasonication Treatment toward Enhanced Electrochemical Properties of Supercapacitor Electrode

Graphene has been gaining tremendous attention as an active material for energy storage devices owing to its large surface area, high electrical conductivity, and high electrochemical stability. However, the restacking of graphene layers during the synthesis process has become one issue that can reduce electrode performance. In this work, the structure of electro-exfoliated graphene (EG) is regulated to improve its electrochemical properties as the supercapacitor electrode using a facile postultrasonication treatment. The ultrasonicated EG exhibited a higher exfoliation degree than the raw EG as indicated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Brunauer-Emmett-Teller (BET) characterization results. Ultrasonicated samples were then tested using three-electrode configuration, which obtained a maximum specific capacitance of 140.5 F g-1 at 0.5 A g-1, which is higher than that of the sample prepared without ultrasonication treatment (79.0 F g-1) at the same current density. Moreover, the cycling performance of ultrasonicated EG was examined using two-electrode measurement yielding the highest capacitance retention of 92.9% after 10,000 cycles at 1 A g-1, which can improve the stability of EG than the sample without ultrasonication (82.2%). These results indicate that ultrasonication can be applied as a straightforward treatment to modify exfoliation degree and lateral size of EG sheets leading to the enhancement of supercapacitor electrode performance.