Development of thin binary and ternary Pd-based alloy membranes for use in hydrogen production

Abstract

The manufacturing, characterisation, and H 2 permeation properties of thin membranes of a variety of binary Pd–Cu (∼5–53 at.% Cu), Pd–TM (∼5 at.% TM = Au, Ru, Mo, Ta, Nb, Y), and ternary Pd–Cu–TM alloys (base alloy ∼ Pd 70Cu 30 where Cu is replaced by various amounts of TM) prepared by magnetron sputtering are reported. From the XRD characterisation it can be concluded that all the membranes prepared by magnetron sputtering exhibit a strong preferential orientation along the 〈1 1 1〉 direction. Among the components investigated, Pd–Au and Pd–Y prove to result in binary Pd-alloys with the highest H 2 permeability. While Pd 95Au 5 shows a similar H 2 permeability compared to pure Pd, Pd 95Y 5 gives a H 2 permeability around 15% larger than pure Pd. Binary Pd-alloy with the addition of 5 at.% Cu, Ru, and Nb gives rise to similar H 2 permeabilities in the range of 80% of pure Pd. The addition of 5 at.% Mo and Ta does not result in binary Pd-alloy materials with a large H 2 permeability. Among the ternary Pd–Cu–TM alloys explored the addition of ∼1 at.% TM always result in an increase in permeability. For the investigated alloys a trend is found showing that the permeability increases and its activation energy decreases with increasing fcc lattice constant of the alloy in the temperature range 300–400 °C. The addition of Ta or Y, resulting in the Pd 73Cu 26Ta 1 and Pd 73Cu 26Y 1 alloys, gives rise to an increase in H 2 permeability of roughly 10 and 45%, respectively. For the Pd 65Cu 21Ag 14 alloy, a H 2 permeability gain of almost 65% is obtained compared to the binary Pd–Cu counterpart at the same Pd content.