Anomalous Charge Transfer Behavior of an Iodide/Triiodide Redox Couple at an Ionic Liquid/Pt-Electrode Interface

作者：Kato Yuki^*; Imanishi Yoshiaki; Taguchi Masaaki; Wayama Muni; Watanabe Tadashi

来源：Journal of Physical Chemistry C, 2011, 115(33): 16637-16643.

DOI：10.1021/jp204812k

Several groups reported that a Grotthus-type bond exchange mechanism for the I-/I-3(-) couples contributes to charge transport and extraordinarily enhances bulk conduction in ionic liquids (Its) beyond mass transport limitation. In the present work, we have studied interfacial charge transfer of the I-/I-3(-) couple at a Pt-electrode surface in one of such ILs demonstrating the extraordinary bulk property, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) added with EMImI and and found that the exchange current density increased exponentially against the redox couple concentration. A closer examination revealed, in light of Marcus microscopic theory, concentration-dependent activation energy is a crucial factor for the anomalous increase in the exchange current density. Raman spectra of the IL suggest that the proximity of I-3(-) and I- should be increased at higher concentrations, resulting in the activation energy decrease that accelerates the charge transfer rate in the IL.

• 出版日期2011-8-25