Stability of the dry proton conductor CsHSO₄ in hydrogen atmosphere

With an objective to assess the suitability of the dry proton conductor cesium hydrogen sulfate (CsHSO₄) as an electrolyte for fuel cells, its chemical stability in H₂ atmosphere in presence of the electrocatalyst Pt/C has been investigated. X-ray diffraction and differential scanning calorimetric (DSC) data indicate that CsHSO₄ decomposes to Cs₂SO₄ and H₂S at 150 °C in H₂ 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 (∼80μm) prepared with poly(vinylidene fluoride) and CsHSO₄ 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 CsHSO₄ 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.