Criteria for the application of high temperature proton conductors in SOFCs

Abstract A critical evaluation of high temperature proton conductors (HTPCs) which might be considered in SOFC applications is presented. A comparison of the conductivities of the best oxygen ion conductors with those of prominent HTPCs shows that a few of the latter may possibly compete in the temperature range 500–700°C. The HTPCs considered here were (a) the classical doped SrCeO 3 , (b) doped BaCeO 3 , (c) doped Sr and Ba zirconates, and (d) complex perovskites of type Ba 3 Ca 1.18 Nb 1.82 O 9− δ . The compounds favored are those with a high enthalpy of solution of water. Generally, the following materials parameters are desirable: deviation from exact oxygen stoichiometry δ ≈0.05; enthalpy of solution of water −Δ H S ≥1.5 eV; effective activation energy for proton transport E H eff t H ≈1.