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Instability of Sulfate and Selenate Solid Acids in Fuel Cell Environments

Merle, Ryan B. and Chisholm, Calum R. I. and Boysen, Dane A. and Haile, Sossina M. (2003) Instability of Sulfate and Selenate Solid Acids in Fuel Cell Environments. Energy and Fuels, 17 (1). pp. 210-215. ISSN 1520-5029. doi:10.1021/ef0201174.

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The chemical and thermal stability of several solid acid compounds under fuel cell operating conditions has been investigated, primarily by thermogravimetric methods. Thermal decomposition of CsHSO_4, a material which has shown promise as an alternative electrolyte for proton exchange membrane (PEM) fuel cells, initiates at ∼175°C under inert conditions. The overall decomposition process can be expressed as 2CsHSO_4 → Cs_2SO_4 + H_2O + SO_3 with Cs_2S_2O_7 appearing as an intermediate byproduct at slow heating rates. Under reducing conditions, chemical decomposition can occur via reaction with hydrogen according to 2CsHSO_4 + 4H_2 → Cs_2SO_4 + 4H_2O + H_2S. In the absence of fuel cell catalysts, this reduction reaction is slow; however, materials such as Pt, Pd, and WC are highly effective in catalyzing the reduction of sulfur and the generation of H_2S. In the case of M_3H(XO_4)_2 compounds, where M = Cs, NH_4, or Rb and X = S or Se, a similar reduction reaction occurs:  2M_3H(XO_4)_2 + 4H_2 → 3M_2XO_4 + 4H_2O + H_2X. In an operational fuel cell based on CsHSO_4, performance degraded with time, presumably as a result of H_2S poisoning of the anode catalyst. The performance loss was recoverable by exposure of the fuel cell to air at 160 °C.

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Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2003 American Chemical Society. Received May 28, 2002. Publication Date (Web): November 28, 2002. Dr. Tregubchenko kindly provided the selenate crystals examined here. This work was supported by the California Energy Commission through the PIER grant program, by the California Institute of Technology through the Grubstake program and by the Office of Naval Research.
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California Energy CommissionUNSPECIFIED
Caltech Grubstake FundUNSPECIFIED
Office of Naval Research (ONR)UNSPECIFIED
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Official Citation:Instability of Sulfate and Selenate Solid Acids in Fuel Cell Environments Ryan B. Merle, Calum R. I. Chisholm, Dane A. Boysen, and Sossina M. Haile Energy & Fuels 2003 17 (1), 210-215 DOI: 10.1021/ef0201174
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67915
Deposited By: George Porter
Deposited On:14 Jun 2016 21:10
Last Modified:11 Nov 2021 03:56

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