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Extraordinarily Efficient Conduction in a Redox-Active Ionic Liquid

Authors

  • Dr. Verner K. Thorsmølle,

    Corresponding author
    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
    2. Current address: Département de Physique de la Matière Condensée, Université de Genève, 24 quai Ernest-Ansermet, CH-1211 Genève (Switzerland)
    • Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
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  • Dr. Guido Rothenberger,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
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  • Dr. Daniel Topgaard,

    1. Division of Physical Chemistry, Chemical Center, Lund University, SE-22100 Lund (Sweden)
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  • Jan C. Brauer,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
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  • Prof. Dai-Bin Kuang,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
    2. Current address: School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, Guangdong, 510275 (China)
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  • Dr. Shaik M. Zakeeruddin,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
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  • Prof. Björn Lindman,

    1. Division of Physical Chemistry, Chemical Center, Lund University, SE-22100 Lund (Sweden)
    2. Departamento de Química, Universidade de Coimbra, Rua Larga, 3004-535-Coimbra (Portugal)
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  • Prof. Michael Grätzel,

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
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  • Prof. Jacques-E. Moser

    1. Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne (Switzerland), Fax: (+41) 216934111
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Abstract

Iodine added to iodide-based ionic liquids leads to extraordinarily efficient charge transport, vastly exceeding that expected for such viscous systems. Using terahertz time-domain spectroscopy, in conjunction with dc conductivity, diffusivity and viscosity measurements we unravel the conductivity pathways in 1-methyl-3-propylimidazolium iodide melts. This study presents evidence of the Grotthuss mechanism as a significant contributor to the conductivity, and provides new insights into ion pairing processes as well as the formation of polyiodides. The terahertz and transport results are reunited in a model providing a quantitative description of the conduction by physical diffusion and the Grotthuss bond-exchange process. These novel results are important for the fundamental understanding of conduction in molten salts and for applications where ionic liquids are used as charge-transporting media such as in batteries and dye-sensitized solar cells.

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