Hydrogen-permeation characteristics of a SrCeO3-based ceramic separation membrane: Thermal, ageing and surface-modification effects

Dense ceramics with mixed protonic-electronic conductivity are of considerable interest for the separation and purification of hydrogen and as electrochemical reactors. In this work, the hydrogen permeability of a Sr0.92Ce0.9Yb0.1O3-delta (SCYb) membrane with a porous Pt catalytic layer on the hydrogen feed-exposed side has been studied over the temperature range 500-804 degrees C employing Ar as the permeate sweep gas. A SiO2-B2O3-BaO-MgO-ZnO-based glass-ceramic sealant was successfully employed to seal the membrane to the dual-chamber reactor. After 14 h of exposure to 10% H-2:90% N-2 at 804 degrees C, the H-2 flux reached a maximum of 33 nmol cm(-2) s(-1), over an order of magnitude higher than that obtained on membranes of similar thickness without surface modification. The permeation rate then decreased slowly and moderately on annealing at 804 degrees C over a further 130 h. Thereafter, the flux was both reproducible and stable on thermal cycling in the range 600-804 degrees C. The results indicate an important role of superficial activation processes in the flux rate and suggest that hydrogen fluxes can be further optimised in cerate-based perovskites. (C) 2009 Elsevier B.V. All rights reserved.