Novel I'd membrane: A composite palladium membrane for hydrogen separation has been fabricated by vacuum-assisted electroless plating. Nanometer-sized palladium grains are packed into a mesoporous gamma-alumina layer located on a macroporous alumina tubular support (see figure). The observed high resistance to hydrogen embrittlement is attributed to the novel membrane configuration and to size-related effects of the palladium grains, and these materials may find use in gas-separation membranes.