Composite membranes based on Ni and Zr-doped BaCeO3 are promising for hydrogen separation. Such composites show high proton conductivity and adequate chemical stability in H2O and CO2, but may be unstable in H2S. In this work, the hydrogen permeation performance of Ni-BaZr0.1Ce0.7Y0.2O3-delta was measured in an H2S-containing atmosphere at 900 degrees C. The hydrogen permeation flux began to degrade in 60 ppm H2S and decreased by about 45% in 300 ppm H2S. After hydrogen permeation tests, X-ray diffraction analysis revealed the formation of BaS, doped CeO2, Ni3S2 and Ce2O2S, Analysis of the microstructure and phase composition. and results of thermodynamic Calculations suggest that reaction between H2S and doped BaCeO3 caused the performance loss of the Ni-BaZr0.1Ce0.7Y0.2O3-delta. (C) 2008 Elsevier B.V. All rights reserved.