Stability of the dry proton conductor CsHSO4 in hydrogen atmosphere

Abstract With an objective to assess the suitability of the dry proton conductor cesium hydrogen sulfate (CsHSO 4 ) as an electrolyte for fuel cells, its chemical stability in H 2 atmosphere in presence of the electrocatalyst Pt/C has been investigated. X-ray diffraction and differential scanning calorimetric (DSC) data indicate that CsHSO 4 decomposes to Cs 2 SO 4 and H 2 S at 150 °C in H 2 atmosphere when it is mixed with Pt/C catalyst, while it is quite stable under identical conditions in the absence of the Pt/C catalyst. Although thin composite membranes (∼80 μm) prepared with poly(vinylidene fluoride) and CsHSO 4 exhibit high proton conductivity at 150–200 °C that is adequate for fuel cell applications, development of compatible non-platinum alloy or transition metal oxide catalysts is needed before CsHSO 4 could be considered as an electrolyte for fuel cells. Also, processing procedures need to be optimized to obtain dense, gas impermeable membranes suitable for fuel cell applications.