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Dehydration behavior of the superprotonic conductor CsH_2PO_4 at moderate temperatures: 230 to 260 °C

Taninouchi, Yu-ki and Uda, Tetsuya and Awakura, Yasuhiro and Ikeda, Ayako and Haile, Sossina M. (2007) Dehydration behavior of the superprotonic conductor CsH_2PO_4 at moderate temperatures: 230 to 260 °C. Journal of Materials Chemistry, 17 (30). pp. 3182-3189. ISSN 0959-9428. https://resolver.caltech.edu/CaltechAUTHORS:20131125-162533351

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Abstract

The dehydration behavior of caesium dihydrogen phosphate CsH_2PO_4 was investigated in the temperature range of 230 °C to 260 °C under high humidity, conditions of particular relevance to the operation of fuel cells based on this electrolyte. The onset temperature of dehydration was determined from changes in ionic conductivity on heating and confirmed by weight change measurements under isothermal conditions. The relationship between the onset temperature of dehydration (T_(dehy)) and water partial pressure (p_(H_2O)) was determined to be log(p_(H_2O)/atm = 6.11(±0.82) − 3.63(±0.42) × 1000/(T_(dehy)/K), from which the thermodynamic parameters of the dehydration reaction from CsH_2PO_4 to CsPO_3 were evaluated. The dehydration pathway was then probed by X-ray powder diffraction analysis of the product phases and by thermogravimetric analysis under slow heating. It was found that, although the equilibrium dehydration product is solid caesium metaphosphate CsPO_3, the reaction occurs via two overlapping steps: CsH_2PO_4 → Cs_2H2P_2O_7 → CsPO_3, with solid caesium hydrogen pyrophosphate, Cs_2H_2P2O_7, appearing as a kinetically favored, transient phase.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1039/B704558CDOIArticle
http://pubs.rsc.org/en/content/articlelanding/2007/jm/b704558cPublisherArticle
ORCID:
AuthorORCID
Haile, Sossina M.0000-0002-5293-6252
Additional Information:© Royal Society of Chemistry 2007. Received 26 Mar 2007, Accepted 16 May 2007. First published online 01 Jun 2007. This article is part of themed collection: New energy materials. This work was supported in part by the Sumitomo Foundation and by the U.S. National Science Foundation (DMR-0435221).
Funders:
Funding AgencyGrant Number
Sumitomo FoundationUNSPECIFIED
NSFDMR-0435221
Subject Keywords:PHASE-TRANSITION FUEL-CELLS CRYSTALS
Issue or Number:30
Record Number:CaltechAUTHORS:20131125-162533351
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20131125-162533351
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42728
Collection:CaltechAUTHORS
Deposited By: Jonathan Gross
Deposited On:02 Dec 2013 23:59
Last Modified:03 Oct 2019 06:01

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