Abstract
The development of the basic understanding of the charge storage mechanisms in electrodes for energy storage applications needs deep characterization of the electrode/ electrolyte interface.Inthis work, we studied the charge of the double layer capacitance at single layer graphene (SLG) electrode used as amodel material, in neat (EMIm-TFSI) and solvated (with acetonitrile) ionic liquid electrodes.The combination of electrochemical impedance spectroscopya nd gravimetric electrochemical quartz crystal microbalance (EQCM) measurements evidence that the presence of solvent drastically increases the charge carrier density at the SLG/ionic liquid interface.T he capacitance is thus governed not only by the electronic properties of the graphene,b ut also by the specific organization of the electrolyte side at the SLG surface originating from the strong interactions existing between the EMIm + cations and SLG surface.E QCM measurements also show that the carbon structure,w ith the presence of sp 2 carbons,a ffects the charge storage mechanism by favoring counter-ion adsorption on SLG electrode versus ion exchange mechanism in amorphous porous carbons.