Influence of anion composition and size on the double layer capacitance for Bi(111)|room temperature ionic liquid interface |
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Authors: | Liis Siinor Karmen Lust Enn Lust |
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Institution: | Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu, Estonia |
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Abstract: | Cyclic voltammetry and electrochemical impedance spectroscopy have been applied for investigation of electrochemically polished Bi(111) electrode in 1-ethyl-3-methyl imidazolium tris(pentafluoroethyl)trifluorophosphate (EMImFAP), 1-ethyl-3-methyl imidazolium tetracyanoborate (EMImTCB) and 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMImBF4) ionic liquids. The region of ideal polarizability, series resistance and capacitance, limiting high-frequency and low-frequency capacitances have been calculated. The lower series capacitance values at electrode potential less negative than the potential of the minimum in the capacitance vs. voltage curve for Bi(111)|EMImFAP than that for EMImBF4, and especially for EMImTCB, have been explained by the bigger diameter of FAP?, higher cation and anion sizes symmetry, and less expressed surface activity (i.e. lower closest approach of the FAP? mass centre to an electrode surface) compared with BF4? and TCB? anions. |
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