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 atmosp heres of O-2 air, N-2 and 10% H-2/He. The presence of water vapor lowers bo th the conductivity values and the activation energies in oxidative atmosph eres, suggesting a mixed proton-electron conducting property of the membran e. The hydrogen permeation flux (J(H2)) increases with temperature at the l ower temperature range and tends to level off at higher temperatures. At co nstant temperature, J(H2) increases with the upstream hydrogen partial pres sure and downstream oxygen partial pressure. J(H2) also increases with decr easing membrane thickness, indicating the bulk diffusion being the rate-lim iting step for hydrogen permeation through thick SCTm membranes. J(H2) as h igh as 3 x 10(-8) mol/cm(2) s was obtained at 900 degrees C with a 1.6 mm t hick SCTm membrane when 10% H-2/He and air were used respectively as the fe ed and sweeping gases. (C) 2000 Elsevier Science B.V. All rights reserved.