A cermet composite membrane composed of a hydrogen-transporting metal (Pd) embedded in a thermodynamically stable, proton-conducting, ceramic matrix (CaZr0.9Y0.1O3-delta) was proposed to achieve the successful combination of high permeability and chemical stability in a CO2-containing atmosphere at elevated temperatures (>600 degrees C). The influence of both applied hydrogen chemical potential gradient and temperature on the hydrogen permeation properties of 0.5-mm-thick, Pd-CZY cermet membranes were studied using dry feed gases with 20-80% H-2. The hydrogen permeation flux increased from 1.3 to 2.3 cm(3)(STP)/min-cm(2) with increasing temperature and p(H2) gradient. The effect of the ceramic matrix on the permeability of the Pd-cermet membranes was also compared. The proton-conducting ceramic matrix exhibited the maximum hydrogen permeation flux, which was attributed to the additional ambipolar hydrogen permeation through the cermet membrane. Finally, the hydrogen permeability in CO2-containing gas streams was investigated using a dry feed gas stream comprised of 30% CO2, 20% H-2 and 50% He. The decrease in hydrogen permeation flux with increasing temperature was ascribed to the decrease in the H-2 content in the feed gas stream as calculated using the Gibbs energy minimization method. (C) 2011 Elsevier B.V. All rights reserved.