Electrical Double Layer Structure in Ionic Liquids: An Understanding of the Unusual Capacitance−Potential Curve at a Nonmetallic Electrode

Md Mominul Islam; Muhammad Tanzirul Alam; T Okajima; T Ohsaka

doi:10.1021/jp8114447

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Electrical Double Layer Structure in Ionic Liquids: An Understanding of the Unusual Capacitance−Potential Curve at a Nonmetallic Electrode

Journal article

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Electrical Double Layer Structure in Ionic Liquids: An Understanding of the Unusual Capacitance−Potential Curve at a Nonmetallic Electrode

Md Mominul Islam, Muhammad Tanzirul Alam, T Okajima and T Ohsaka

Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter, Vol.113(9), pp.3386-3389

2009

DOI: https://doi.org/10.1021/jp8114447

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Abstract

This study describes the causes of a U-like capacitance-potential (C-E) curve observed at nonmetallic electrode/ionic liquids (ILs) interfaces, in contrast to those observed at metal electrodes and expected according to the Kornyshev theory (Kornyshev, A. A. J. Phys. Chem. B2007, 111, 5545). Several C-E curves were measured at glassy carbon (GC) and highly oriented pyrolytic graphite (HOPG) electrodes in three different ILs with inherent ionic concentrations of 6.4, 3.3, and 1.7 M. The minimum capacitance value (2.2 μF cm-2) at the HOPG electrode is significantly lower than those at GC or metal electrodes (>10 μF cm-2). The degree of curvature of the "U-like" curve measured at the GC electrode decreases in the ILs with low inherent ionic concentrations. This observation is in agreement with the theoretical curves deduced by considering both semiconductor and Kornyshev theories and the inherent properties (concentrations, sizes of ions, dielectric constant, etc.) of ILs used. The capacitance at the GC electrode exhibits a complex potential dependence, being different from those at HOPG and metal electrodes that were explained using semiconductor and Kornyshev theories, respectively. Depending on the characteristics of ILs, both concepts of semiconductor theory and Kornyshev's model may be required to explain the C-E curves at the GC electrode.

Details

Title: Electrical Double Layer Structure in Ionic Liquids: An Understanding of the Unusual Capacitance−Potential Curve at a Nonmetallic Electrode
Authors: Md Mominul Islam (Author) - Tokyo Institute of Technology, Japan
Muhammad Tanzirul Alam (Author) - Tokyo Institute of Technology, Japan
T Okajima (Author) - Tokyo Institute of Technology, Japan
T Ohsaka (Author) - Tokyo Institute of Technology, Japan
Publication details: Journal of Physical Chemistry Part C: Nanomaterials, Interfaces and Hard Matter, Vol.113(9), pp.3386-3389
Publisher: American Chemical Society
Date published: 2009
DOI: 10.1021/jp8114447
ISSN: 1932-7447
Organisation Unit: School of Science and Engineering - Legacy; University of the Sunshine Coast, Queensland; National Centre for Timber Durability and Design Life
Language: English
Record Identifier: 99450125902621
Output Type: Journal article

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Web Of Science research areas: Chemistry, Physical; Materials Science, Multidisciplinary; Nanoscience & Nanotechnology