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Z. Naturforsch. 66a, 668 – 674
(2011)
doi:10.5560/ZNA.2011-0039
Electrochemical Behaviour of Hydrogen in Low-Viscosity Phosphonium Ionic Liquids
1 Graduate School of Environment and Information Sciences, Yokohama National University, 79-2 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Japan
2 Department of Materials Science, Wakayama National College of Technology, 77 Noshima, Nada-cho, Gobo, Wakayama, 644-0023, Japan
3 Nippon Chemical Industrial Co., Ltd., 9-11-1 Kameido, Koto-ku, Tokyo, 136-8515, Japan
Received July 4, 2011
Reprint requests to: M. M.; E-mail:
mmatsumi@ynu.ac.jp
The electrochemical and diffusive properties of hydrogen in low-viscosity phosphonium ionic liquids were investigated by the electrochemical methods such as cyclic voltammetry and chronoamperometry. The hydrogen redox reactions were concluded to be a quasi-reversible system in phosphonium-based ionic liquids. The diffusion coefficients of hydrogen in these ionic liquids were of the order of 10−10 m2 s−1 at 25 °C. Additionally, the obtained activation energy of the diffusion process for hydrogen was 11.2–15.9 kJ mol−1 estimated from the temperature dependence of the diffusion coefficients.
A new type of proton conducting medium such as triethylphosphonium bis(trifluoromethylsulfonyl)amide was synthesized by the neutralization reaction, because the trialkylphosphine-based ionic liquids with good stability at higher temperature and high conductivity were appropriate candidates. This proton conducting membrane containing the ionic liquids with trialkylphosphine-based cations and the polyvinylidenefluoride-co-hexafluoropropylene has been fabricated in the present study. The proton conducting membrane exhibits relatively high ionic conductivity along with good mechanical stability.
Key words: Ionic Liquid; Phosphonium Cations; Hydrogen; Diffusion Coefficients.