Thin palladium membrane (less than 5-μm thick) supported on porous α-alumina and yttria stabilized zirconia (YSZ) was prepared for high temperature hydrogen separation. Hydrogen permeation flux across palladium/α-alumina composite membrane appreciably decreased during the gas permeation test at elevated temperatures (650-850 °C). It is probably due to the hydrogen-induced strong interaction between palladium membrane and α-alumina support. Conversely, such a strong interaction was not found between YSZ support and palladium membrane. Palladium/YSZ composite membrane exhibited a steady permeation flux of hydrogen at 650 °C. Copyright © (2010) by the North American Membrane Society.