The electrochemical characteristics for electrochemically polished Bi(1 1 1) electrode in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF(4)) 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 (C-s), double layer capacitance, adsorption capacitance, diffusion resistance and charge transfer resistance have been calculated and analyzed. C-s values were calculated from experimental Nyquist plots at constant ac frequencies and C-s depends on the composition of ionic liquid, electrode potential and ac frequency. However noticeable dependence of C-s 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. (c) 2012 Elsevier B.V. All rights reserved.