Electrochemical Properties of Bi(111)|1-Ethyl-3-Methylimidazolium Tetracyanoborate and 1-Ethyl-3-Methylimidazolium Iodide Interface

Room temperature ionic liquids (RTILs) can sustain substantially higher cell potentials (ΔE) in electrochemical cells without decomposing. For electrochemical double layer capacitors (EDLCs) the widening of the cell potential increases exponentially the energy and power densities. RTILs can be use as electrolytes in modern electrochemical energy devices, such as capacitors, solar cells, batteries and fuel-cells. ^1–4

In this work the cyclic voltammetry and electrochemical impedance spectroscopy methods have been applied to investigate the electrical double layer formation and adsorption kinetics parameters of iodide anions at the electrochemically polished Bi(111) electrode surface. The ionic liquid solution was prepared in order to increase the differential capacitance of the system. Therefore 1 wt% 1-ethyl-3-methylimidazolimu iodide (EMImI) was added to 1-ethyl-3-methylimidazolium tetracyanoborate (EMImTCB).

Analysis of current density (j) vs. electrode potential (E) dependencies shows that the Bi(111) electrode is ideally polarizable within the potential range from -1.0 to -0.2 V for 1 wt% vs. Ag| AgCl.

The measured ideal polarizability region is in a good agreement with impedance data. The mixed kinetic processes take place on both systems (Bi(111)|EMImTCB and Bi(111)|EMImTCB + 1%EMImI). Higher capacitance values were obtained for the Bi(111)|EMImTCB + 1%EMImI system. Our recent studies have shown that the addition of specifically adsorbed iodide ions strongly influence the electrochemical characteristics of RTILs systems. ¹

Acknowledgments: This study was partially funded by the Estonian Science Foundation Grants 7791, 8357 and 8786, Estonian Energy Technology Program project SLOKT10209T, Estonian Basic Research project SF0180002s08 and Estonian Centers of Excellence in Science project: High-technology Materials for Sustainable Development TK117

References:

1. C. Siimenson, L. Siinor, K. Lust, and E. Lust, J. Electroanal. Chem., 730, 59–64 (2014).

2. T. Tooming et al., J. Electrochem. Soc., 161, A222–A227 (2014).

3. L. Siinor, J. Poom, C. Siimenson, K. Lust, and E. Lust, J. Electroanal. Chem., 719, 133–137 (2014).

4. L. Siinor, K. Lust, and E. Lust, Electrochem. Commun., 12, 1058–1061 (2010).