Experimental and theoretical studies of hydrogen permeation for doped strontium cerates

Non-galvanic hydrogen permeation properties of SrCe(0.95)Yb(0.05)O(3-alpha), (SCYb-5) and SrCe(0.95)Tm(0.05)O(3-alpha) (SCTm-5) dense membranes were investigated in a 'wet' hydrogen atmosphere where water vapour partial pressures were well defined and monitored for the entire duration of the experiments. The theoretical modelling of hydrogen permeation flux for SCYb-5 and SCTm-5 was also undertaken, and compared with experimental results. The parameter tuning was also performed by fitting the model to the experimental data obtained in this study. The experimental hydrogen permeation flux for SCYb-5 and SCTm-5 dense membranes was 6.8e(-9) mol/cm(2)/s and 7.1e(-9) mol/cm(2)/s, respectively, under the upstream hydrogen partial pressure of 0.25 atm (25%H(2)/Ar) at 900 degrees C. As expected, the hydrogen permeation flux increases with the increase in the upstream hydrogen partial pressures, reaching the maximum flux of 1.4e(-8) mol/cm(2)/s and 1.6e(-8) mol/cm(2)/s, for SCYb-5 and SCTm-5 respectively, under the upstream hydrogen partial pressure of 1 atm (100%H(2)) at 900 degrees C. Previous modelling used hydrogen permeation data collected by others in a permeation test conducted in a 'dry' hydrogen atmosphere (with unknown water vapour pressures). The modelled hydrogen permeation flux agreed well with the experimental data attained in this study, for both SCYb-5 and SCTm-5 samples. The parameter tuning further improved the model predictions for those samples. It was apparent that the modelled hydrogen flux agreed better with the experimental data obtained in this study (i.e. in a wet hydrogen atmosphere with known water vapour pressures). (C) 2010 Elsevier B.V. All rights reserved.