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

The electrical conduction and hydrogen permeation properties of dense SrCe0.95Tm0.05O3-delta (SCTm) membranes were studied in the temperature range of 600-950 degrees 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(H2)) increases with temperature at the lower temperature range and tends to level off at higher temperatures. At constant temperature, J(H2) increases with the upstream hydrogen partial pressure and downstream oxygen partial pressure. J(H2) also increases with decreasing membrane thickness, indicating the bulk diffusion being the rate-limiting step for hydrogen permeation through thick SCTm membranes. J(H2) as high as 3 x 10(-8) mol/cm(2) s was obtained at 900 degrees 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. (C) 2000 Elsevier Science B.V. All rights reserved.