Electrical conduction and hydrogen permeation through mixed proton–electron conducting strontium cerate membranes

Abstract

The electrical conduction and hydrogen permeation properties of dense SrCe 0.95Tm 0.05O 3− δ (SCTm) membranes were studied in the temperature range of 600–950°C. The conductivity measurement shows that the temperature dependence of SCTm conductivity obeys the Arrhenius relationship in atmospheres of O 2, air, N 2 and 10% H 2/He. The presence of water vapor lowers both the conductivity values and the activation energies in oxidative atmospheres, suggesting a mixed proton–electron conducting property of the membrane. The hydrogen permeation flux ( J H 2 ) increases with temperature at the lower temperature range and tends to level off at higher temperatures. At constant temperature, J H 2 increases with the upstream hydrogen partial pressure and downstream oxygen partial pressure. J H 2 also increases with decreasing membrane thickness, indicating the bulk diffusion being the rate-limiting step for hydrogen permeation through thick SCTm membranes. J H 2 as high as 3×10 −8 mol/cm 2 s was obtained at 900°C with a 1.6 mm thick SCTm membrane when 10% H 2/He and air were used respectively as the feed and sweeping gases.