The disclosure provides an H2 separation membrane comprised of an alloy having the composition Cu.sub.(100-x-y)Pd.sub.xM.sub.y, where x is from about 35 to about 50 atomic percent and where y is from greater than 0 to about 20 atomic percent, and where M consists of magnesium, yttrium, aluminum, titanium, lanthanum, or combinations thereof. The M elements act as strong stabilizers for the B2 phase of the alloy, and extend the critical temperature of the alloy for a given hydrogen concentration and pressure. Due to the phase stabilization and the greater temperature range over which a B2 phase can be maintained, the alloy is well suited for service as a H2 separation membrane, particularly when applicable conditions are established or cycled above about 600.degree. C. over the course of expected operations. In certain embodiments, the B2 phase comprises at least 60 estimated volume percent of the alloy at a steady-state temperature of 400.degree. C. The B2 phase stability is experimentally validated through HT-XRD.
The United States Government has rights in this invention pursuant to the employer-employee relationship of the Government to the inventors as U.S. Department of Energy employees and site-support contractors at the National Energy Technology Laboratory.