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Direct View on Nanoionic Proton Mobility

Authors

  • Wing K. Chan,

    1. Fundamental Aspects of Materials and Energy, Department of Radiation, Radionuclides, and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands
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  • Lucas A. Haverkate,

    1. Fundamental Aspects of Materials and Energy, Department of Radiation, Radionuclides, and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands
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  • Wouter J. H. Borghols,

    1. Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at FRM II, 85747 Garching, Germany
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  • Marnix Wagemaker,

    1. Fundamental Aspects of Materials and Energy, Department of Radiation, Radionuclides, and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands
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  • Stephen J. Picken,

    1. Nano structured Materials, Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
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  • Ernst R. H. van Eck,

    1. Department of Physical Chemistry – Solid State NMR, IMM, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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  • Arno P. M. Kentgens,

    1. Department of Physical Chemistry – Solid State NMR, IMM, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
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  • Mark R. Johnson,

    1. Institut Laue-Langevin (ILL), BP 156, 38042 Grenoble, Cedex 9, France
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  • Gordon J. Kearley,

    1. Bragg Institute, Building 87, Australian Nuclear Science and Technology Organisation, PMB Menai, NSW2234, Australia
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  • Fokko M. Mulder

    Corresponding author
    1. Fundamental Aspects of Materials and Energy, Department of Radiation, Radionuclides, and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands
    • Fundamental Aspects of Materials and Energy, Department of Radiation, Radionuclides, and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft, The Netherlands.
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Abstract

The field of nanoionics is of great importance for the development of superior materials for devices that rely on the transport of charged ions, like fuel cells, batteries, and sensors. Often nanostructuring leads to enhanced ionic mobilities due to the induced space-charge effects. Here these large space-charge effects occurring in composites of the proton-donating solid acid CsHSO4 and the proton-accepting TiO2 or SiO2 are studied. CsHSO4 is chosen for this study because it can operate effectively as a fuel-cell electrolyte at elevated temperature while its low-temperature conductivity is increased upon nano­structuring. The composites have a negative enthalpy of formation for defects involving the transfer of protons from the acid to the acceptor. Very high defect densities of up to 10% of the available sites are observed by neutron diffraction. The effect on the mobility of the protons is observed directly using quasielastic neutron scattering and nuclear magnetic resonance spectroscopy. Surprisingly large fractions of up to 25% of the hydrogen ions show orders-of-magnitude enhanced mobility in the nanostructured composites of TiO2 or SiO2, both in crystalline CsHSO4 and an amorphous fraction.

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