Electroanalytical characterization of electrochemical capacitor systems using step potential electrochemical spectroscopy

Abstract

Herein we demonstrate the application of step potential electrochemical spectroscopy (SPECS) to the electroanalytical characterization of a symmetrical activated carbon non-aqueous (tetraethylammonium tetrafluoroborate in acetonitrile) electrochemical capacitor device. Through the use of a Ag/Ag+ reference electrode, individual electrode potentials were measured showing that even though it is a symmetrical device, polarization on the positive electrode was always greater than the negative electrode, implying that the negative electrode capacitance is greater. Deconvolution of the i-t transients from the SPECS experiment across the device voltage window can be accomplished in a similar fashion to the study of a single electrode, in which case geometric and porous capacitances, as well as diffusion and residual processes are identified. Similarly, the components of the i-t transients can be converted into voltametric data, providing access to individual electrode performance over a wide range of sweep rates in the device. The inclusion of a sensing electrode between he positive and negative electrodes is also described, providing insight into electrolyte fluxes and electrode stability within the device.