Influence of alloy composition and membrane fabrication on the pressure dependence of the hydrogen flux of palladium-copper membranes

Several Pd-Cu composite membranes with different alloy compositions were made by electroless deposition on ceramic supports, and permeation rates for pure H-2 and N-2 were measured. The alloy composition was found to have a strong influence on the hydrogen permeance for these membranes. The effect of alloy composition on the H2 permeance was found to be in qualitative agreement with literature reports. A Pd60Cu40 composite membrane was prepared, and it was found to exhibit a permeance of 0.32 cm(3) (STP)/cm(2.)s(.)cmHg(1/2) at 350 degreesC, the highest among all of the membranes studied. Also, we present experimental data from the testing of another Pd-Cu composite membrane that showed an ideal selectivity for H-2 over N-2 of well over 7000 and discuss how this outcome might be related to changes in the membrane fabrication method. The influence of temperature and alloy composition on the exponential dependence (n value) of hydrogen diffusion through palladium-copper composite membranes is also discussed. Values for n oscillated between 0.5 and slightly over 1, indicating the influence of different transport mechanisms. X-ray diffraction and atomic force microscopy were used to study the surface morphology and to understand the differences in transport properties between the palladium-copper composite membranes prepared in this work and Pd60Cu40 foils commonly used.