Instability of sulfate and selenate solid acids in fuel cell environments

Ryan B. Merle, Calum R I Chisholm, Dane A. Boysen, Sossina M. Haile*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

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 CsHSO4, 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 2CsHSO4 → Cs2SO4 + H2O + SO3 with Cs2S2O7 appearing as an intermediate byproduct at slow heating rates. Under reducing conditions, chemical decomposition can occur via reaction with hydrogen according to 2CsHSO4 + 4H2 → Cs2SO4 + 4H2O + H2S. 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 H2S. In the case of M3H(XO4)2 compounds, where M = Cs, NH4, or Rb and X = S or Se, a similar reduction reaction occurs: 2M3H(XO4)2 + 4H2 → 3M2XO4 + 4H2O + H2X. In an operational fuel cell based on CsHSO4, performance degraded with time, presumably as a result of H2S poisoning of the anode catalyst. The performance loss was recoverable by exposure of the fuel cell to air at 160°C.

Original languageEnglish (US)
Pages (from-to)210-215
Number of pages6
JournalEnergy and Fuels
Volume17
Issue number1
DOIs
StatePublished - Jan 1 2003

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Energy Engineering and Power Technology
  • Fuel Technology

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