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Superprotonic behavior of Cs_2(HSO_4)(H_2PO_4) – a new solid acid in the CsHSO_4–CsH_2PO_4 system

Chisholm, Calum R. I. and Haile, Sossina M. (2000) Superprotonic behavior of Cs_2(HSO_4)(H_2PO_4) – a new solid acid in the CsHSO_4–CsH_2PO_4 system. Solid State Ionics, 136 . pp. 229-241. ISSN 0167-2738. http://resolver.caltech.edu/CaltechAUTHORS:20131125-162531086

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Abstract

Investigations into the CsHSO₄–CsH₂PO₄ system have yielded a new solid acid, Cs₂(HSO₄)(H₂PO₄), with a superprotonic phase transition that occurs over the temperature range 61–105°C. In the room temperature structure, the SO₄ and PO₄ groups are randomly arranged on a single tetrahedral anion site. Hydrogen bonds are distributed through the structure so as to generate a two-dimensional network quite different from that of other cesium sulfate phosphate solid acids. The transition in Cs₂(HSO₄)(H₂PO₄) takes place by a unique two-step process, occurs at an unusually low temperature, is accompanied by a large heat of transformation, ΔH=44±2 J/g, and exhibits significant hysteresis. High temperature X-ray powder diffraction (XRD) and infrared (IR) spectroscopy revealed that the high temperature phase is cubic, with a₀=4.926(5)Å, and likely takes on a CsCl structure, with Cs atoms at the corners of a simple cubic unit cell, and XO₄ groups (X=P or S) at the center. The conductivity in the high temperature phase at 110°C is 3×10⁻³ Ω⁻¹ cm⁻¹, and the activation energy for proton transport is 0.37(1) eV. These values suggest that proton transport is facilitated by rapid XO₄ group reorientations in the cubic phase of Cs₂(HSO₄)(H₂PO₄), as is known to occur in the high temperature, tetragonal phase of CsHSO₄.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/S0167-2738(00)00315-5DOIArticle
http://www.sciencedirect.com/science/article/pii/S0167273800003155PublisherArticle
ORCID:
AuthorORCID
Haile, Sossina M.0000-0002-5293-6252
Alternate Title:Superprotonic behavior of Cs2(HSO4)(H2PO4) – a new solid acid in the CsHSO4–CsH2PO4 system
Additional Information:Proceedings of the 12th International Conference on Solid State Ionics. Copyright © 2000 Elsevier Science B.V. Available online 30 November 2000. The authors are pleased to acknowledge the financial support the National Science Foundation via a National Young Investigator Award to SMH. Additional funding was provided by the Irvine Foundation. The authors thank Professor George Rossman and Liz Miura at the California Institute of Technology for their kind guidance with infrared analyses and Paul Wagner for his assistance with high temperature powder diffractometry.
Funders:
Funding AgencyGrant Number
NSFUNSPECIFIED
Irvine Foundation UNSPECIFIED
Subject Keywords:Ionic conductivity; Hydrogen bonding; IR spectroscopy; Proton conductivity; Anisotropy; Phase transition; Cesium hydrogen sulfate
Record Number:CaltechAUTHORS:20131125-162531086
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20131125-162531086
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42710
Collection:CaltechAUTHORS
Deposited By: Jonathan Gross
Deposited On:27 Nov 2013 22:00
Last Modified:16 Sep 2015 02:03

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