Multilayer metal membranes for hydrogen separation

A novel multilayer metal membrane has been developed that can be used for the separation of ultra-high purity hydrogen from impure feed streams. The membrane is comprised of very thin layers of dense palladium film deposited on both sides of a thin Group V metal foil, ion-milled prior to the deposition of the palladium. This membrane operates at elevated temperatures on the order of 300 °C and is capable of high rates of hydrogen flow. Flows are dependent on the pressure differential applied to the membrane, but flows of 100 standard cubic centimeters of hydrogen per minute per square centimeter of membrane and higher are regularly observed with differentials of under one atmosphere. Testing of the membrane for a period of 775 h showed stable flows under constant conditions. A membrane system has been successfully applied to a proton exchange membrane fuel cell and was tested using a pseudo-reformate feed stream containing 1% carbon monoxide without any degradation in performance.