Electrical Double Layer Capacitance at Bi(111)∣1-Ethyl-3-methylimidazolium Tetrafluoroborate Interface as a Function of the Electrode Potential

Abstract

The influence of the electrode potential on the Bi͑111͒ ͉ 1-ethyl-3-methylimidazolium tetrafluoroborate interface has been studied by cyclic voltammetry and electrochemical impedance. The weak deviation of the system from capacitive behavior for the ideally flat electrode has been established within the moderate electrode potential region from Ϫ0.9 to Ϫ0.1 V vs Ag ͉ AgCl in 1-ethyl-3-methylimidazolium tetrafluoroborate. The parallel faradaic processes are possible outside the potential region from Ϫ0.9 to Ϫ0.1 V. The results obtained for the Bi͑111͒ ͉ 1-ethyl-3-methylimidazolium tetrafluoroborate interface have been compared with those for gold, mercury, and glassy carbon electrodes.Recent research activity of room-temperature ionic liquids ͑RTILs͒, initiated by their potential applications in various modern electrochemical power systems, created interest in the interface between ionic liquids and metal 1-12 as well as carbon, including nanoporous carbon electrodes. [13][14][15] Despite the extensive discussions about whether the electrical double layer ͑edl͒ at the metal ͉ RTIL interface is fundamentally different from or similar to that extensively studied at the metal ͉ electrolyte solution interface, 11,12,[15][16][17][18] our knowledge of the metal ͉ RTIL interface is still sketchy because there is no systematic impedance and capacitance characteristics for edl in single-crystal electrodes. Detailed theoretical papers have been written by Kornyshev et al.;11,12,18 however, the verification of these models needs a detailed systematic analysis of experimental data not existing at present.The electrical double layer capacitor ͑EDLC͒ characteristics 13-15,19-27 have been discussed and it has been established that, due to the limited solubility of salts ͑from 1.5 to 1.8 M͒, a decrease in electrolyte conductivity takes place, caused by the adsorption of a large amount of ions at the electrodes with a high specific surface area. However, there are some possibilities to increase the concentration of ions by using RTILs ͑with molar concentration 4-6 M͒ in EDLCs instead of the traditional electrolyte solution. [19][20][21][22][23][24][25][26][27] There are only few publications devoted to edl capacitance and impedance measurements on the geometrically flat, well-defined electrodes in RTILs. 28-31 Surprisingly low series capacitance ͑C s ͒ values ͑from 1 to 8 F cm −2 ͒ have been calculated for various metal electrodes, which is not easy to explain theoretically. 11,12,[16][17][18] Such low values of C s probably indicate surface blocking of the electrode surface by the irreversible adsorption of contaminants. The adsorption/ desorption kinetics of RTIL ions has not been studied systematically; 31 however, the kinetics of probable electrostatic adsorption with partial charge transfer and distribution of ions near the electrode surface, over screening, and lattice saturation effects 11,18 are extremely important for engineering the high power density supercapacitors. [13][14][15][19][20][21][22][23][24][25][26][27] Anoth...

Electrochemical Characterization of Iodide Ions Adsorption Kinetics at Bi(111) Electrode from Three-Component Ionic Liquids Mixtures

“…The preparation of RE and electrochemical polishing of the WE and good long-term cycling stability has been described in published publications. 9,11,[17][18][19] RE was connected to the WE compartment through a Luggin capillary.…”

“…The preparation of RE and electrochemical polishing of the WE and good long-term cycling stability has been described in published publications. 9,11,[17][18][19] RE was connected to the WE compartment through a Luggin capillary.All the measurements were carried out inside a glove box (H 2 O < 1.0 ppm, O 2 < 1.0 ppm). Cyclic voltammetry and impedance spectroscopy were used for electrochemical characterization of the Bi(111) | RTILs mixture interface (using Autolab PGSTAT 320 and FRA II).…”

Static Capacitance at the Electrochemical Liquid-liquid Interface Between Ionic Liquids and Eutectic Ga-In Alloy Measured Using the Pendant Drop Method

“…39,40 The pendant drop method is a static method unlike other methods such as EIS, [41][42][43][44][45][46][47][48][49][50] drop time method, 42,44,51-54 and drop weight method 55 utilized to study the EDL of ILs, and therefore, the measurements are not affected by the ultraslow dynamics described above. C dc by the pendant drop method enabled us to reproduce the one-hump 39,40 and two-hump 39 camel-shape behavior predicted by the theories (see open symbols around E pzc , vertical dotted lines, in Figs.…”

Influence of cation chemical composition and structure on the double layer capacitance for Bi(111)|room temperature ionic liquid interface

“…Therefore, our recent research is focused on the use of non-aqueous electrolytes and RTIL for high energy-power density EDLCs based on micro-meso-porous carbon [2][3][4][5]. However, electrochemical measurements using porous carbon electrodes are more complicated, time consuming and expensive, and thereof the testing measurements have been also carried out on the electrochemically polished single crystal Bi(111) electrode [6][7][8] in order to investigate the influence of the chemical composition of ions, their surface orientation, and possible dependence of the closest approach of RTIL ions onto the electrode surface [9][10][11]. Bismuth (1 1 1) plane is known to be catalytically, chemically and electrochemically inactive, and for this reason was proposed as a replacement of mercury.…”