Dicationic Ionic Liquid: Insight in the Electrical Double Layer Structure at mercury, glassy carbon and gold surfaces

In this work we report for the first time differential capacitance curves measured at imidazolium dicationic ionic liquid/electrode interfaces as a new strategy to understand the interfacial behaviour of ionic liquids (IL) near a charged electrode. The ionic liquid studied (1,5-bis(3-dimethylimidazolium)pentane di-bis(trifluoromethylsulfonyl)imide [C5(MIM)2][Tf2N]2) contains a cation with two positively charged imidazolium rings substituted with a methyl group connected by a pentane linkage alkyl chain length providing a new cationic structure variation. The comparison with the analogue monocationic ionic liquids showed that the dicationic liquid has a wider electrochemical polarization window and a more positive potential of zero charge at a Hg electrode. Differential capacity curves measured at dicationic ionic liquid/Hg interface show similar shape compared with analogous monocationic ionic liquids and revealed to be very sensitive to the electrode material.