Palladium based film-type cermet membranes for hydrogen separation

Abstract

Thin-film type cermet (i.e., ceramic–metal composite) membranes were made by a paste painting method, and their hydrogen transport properties were evaluated. The hydrogen permeability of a 30 μm thick Pd/YSZ (palladium/yttrium-stabilized zirconia) film was compared with that of Pd foil (thickness of 0.1 mm). To test the reproducibility of the results and stability of the Pd/YSZ film, the film's permeability was measured over a period of ∼300 h as a function of temperature, gas flow rate, and hydrogen partial pressure. In addition, the influence of a porous alumina substrate was investigated by measuring the hydrogen flux of the Pd foil with and without an Al₂O₃ substrate in front of the foil. The differences between the hydrogen permeability of the cermet film and that of the Pd foil are discussed. As additional practical information about the cermet film, its thermal expansion behavior was studied in air and in nitrogen, and changes in its microstructure were examined during stability tests. Taken together, the results indicate that thin-film Pd/YSZ cermet membranes can meet the requirements of hydrogen transport membranes.