Influence of Analysis Method on the Experimentally Observed Capacitance at the Gold-Ionic Liquid Interface

Diverse results have been reported on the differential capacitance of the metal-ionic liquid interface. Here the effect of the analysis method on the experimentally observed double layer capacitance is evaluated. A fast Fourier transform impedance spectroscopy technique allows the impedance-DC bias landscape of three 1-alkyl-3-methylimidazolium salts to be explored over a wide range of frequencies in a fraction of the time required for traditional impedance techniques. Analysis of this data set using four different methods found in the literature demonstrates how the assumptions inherent to each method alter the capacitance-DC bias curve. Careful consideration of these assumptions is necessary to compare results across the literature and understand the properties inherent to the solid-ionic liquid interface.