Influence of temperature on the electrochemical characteristics of Bi(1 1 1)|ionic liquid interface

The electrochemical characteristics for electrochemically polished Bi(1 1 1) electrode in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) within temperature range from 298 K to 348 K were studied using electrochemical impedance spectroscopy and cyclic voltammetry. The region of ideal polarizability, series capacitance (Cs), double layer capacitance, adsorption capacitance, diffusion resistance and charge transfer resistance have been calculated and analyzed. Cs values were calculated from experimental Nyquist plots at constant ac frequencies and Cs depends on the composition of ionic liquid, electrode potential and ac frequency. However noticeable dependence of Cs on temperature can be seen only within the low ac frequency range from 1 Hz to 0.1 Hz. Based on the fitting results of impedance data, the restructuring of electrical double layer and adsorption of large organic ions is a kinetically slow process.