2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 3. Gaune-Escard Intl. Symp. / Molten Salt and Ionic Liquid

Editors:Kongoli F, Fehrmann R, Gadzuric S, Gong W, Seddon KR, Malyshev V, Iwata S
Publisher:Flogen Star OUTREACH
Publication Year:2017
Pages:151 pages
ISBN:978-1-987820-65-2
ISSN:2291-1227 (Metals and Materials Processing in a Clean Environment Series)
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    Specific Electrical Conductivity in Solid and Molten CsH2PO4 and Cs2H2P2O7 A Potentially New Electrolyte for Water Electrolysis at ~225-400 C

    Aleksey Nikiforov1; Rolf Berg2; Niels Bjerrum3;
    1TECHNICAL UNIVERSITY OF DENMARK, Kongens Lyngby, Denmark; 2TECHNICAL UNIVERSITY OF DENMARK, DEPARTMENT OF CHEMISTRY, Lyngby, Denmark; 3TECHNICAL UNIVERSITY OF DENMARK, DEPARTMENT OF ENERGY CONVERSION AND STORAGE, Lyngby, Denmark;
    Type of Paper: Regular
    Id Paper: 197
    Topic: 13

    Abstract:

    Water electrolysis represents an attractive way of converting surplus electrical energy into hydrogen by balancing the electric grid when an increasing fraction of the power input originates from fluctuating renewable sources. Excess energy storage using fuels such as synthesis gas and methanol in electrochemical cells operating at intermediate temperature have several advantages, among which are: improved catalytic activity, effective use of waste heat, and prevention of permeability through the electrolyte. Cesium dihydrogen phosphate conductivity would be one of the key parameters directly influencing the performance of water electrolyser. Therefore the specific conductivity of this electrolyte should be carefully characterized, as it depends on several parameters, such as temperature, the exact chemical composition of the electrolyte, and humidity. All these parameters are reflected in the associated water vapor pressure above the salt. In this work, the conductivity of solid state and molten CsH2PO4 was carefully examined in the temperature interval 220 - 400 C with 2 C steps and under its own vapor pressure of H2O in a sealed ampoule system. Additionally, conductivities of mixtures composed of CsH2PO4 and different contents of water and/or CsPO3 were examined and compared with values corresponding to pure CsH2PO4. H-cells fabricated from quartz were used to determine the conductivity of the synthesized CsH2PO4 and mixtures of it with water or CsPO3. Molten CsH2PO4 above 347 C and under its own vapor pressure represents a liquid with an extremely high conductivity of 0.2 S*cm-1. By further heating from that temperature the conductivity still increases until it reaches values above 0.25 S*cm-1 at 400 C. This increase in conductivity from below 0.1 S*cm-1 below 347 C (solid state) to 0.25 S*cm-1 at 400 C (molten state) opens new perspectives for possible applications as electrolyte in energy conversion systems at elevated temperatures.

    Keywords:

    Characterization; Compounds; Conductivity; Energy; Environment; Materials; Sustainability; Tungsten;

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    Cite this article as:

    Nikiforov A, Berg R, Bjerrum N. (2017). Specific Electrical Conductivity in Solid and Molten CsH2PO4 and Cs2H2P2O7 A Potentially New Electrolyte for Water Electrolysis at ~225-400 C. In Kongoli F, Fehrmann R, Gadzuric S, Gong W, Seddon KR, Malyshev V, Iwata S (Eds.), Sustainable Industrial Processing Summit SIPS 2017 Volume 3. Gaune-Escard Intl. Symp. / Molten Salt and Ionic Liquid (pp. 130-131). Montreal, Canada: FLOGEN Star Outreach