Influence of cation chemical composition and structure on the double layer capacitance for Bi(1 1 1)|room temperature ionic liquid interface

Cyclic voltammetry, electrochemical impedance spectroscopy, and computational chemistry methods have been applied for investigation of electrochemically polished Bi(1 1 1) electrode in 1-butyl-4-methylpyridinium tetrafluoroborate (BMPyBF₄) ionic liquid. The region of ideal polarizability, series resistance and capacitance, limiting high-frequency and low-frequency capacitances have been obtained and compared with those established for 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF ₄). Differently from Bi(111)|EMImBF₄ interface, noticeably more expressed influence of the mass transfer limited step on the electrical double layer formation kinetics has been demonstrated and explained by the higher viscosity of BMPyBF₄. Possible reasons of the lower values of series capacitance for Bi(111)|BMPyBF₄ compared with Bi(1 1 1)|EMImBF₄ interface has been examined on the basis of modern theoretical models.