Charge Storage Mechanisms of Single-Layer Graphene in Ionic Liquid

Graphene-based carbon materials are promising candidates for electrical double-layer (EDL) capacitors, and there is considerable interest in understanding the structure and properties of the graphene/electrolyte interface. Here, electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (EQCM) are used to characterize the ion fluxes and adsorption on single-layer graphene in neat ionic liquid (EMI-TFSI) electrolyte. It is found that a positively charged ion-species desorption and ion reorganization dominate the double-layer charging during positive and negative polarizations, respectively, leading to the increase in EDL capacitance with applied potential.