A comparison of the performance and stability of Pd/BCC metal composite membranes for hydrogen purification

Composite membranes were fabricated by sputtering 100 nm of Pd on to both sides of dense BCC metal foils (V, Ta, Nb). Under pure H2 gas testing at 500 °C the maximum permeability of all three metals exceeds previously reported values and closely approach theoretical limits. However, the stability of each membrane varied significantly due to unique failure mechanisms. Pd/V membranes failed quickly (<20 h) due to a combination of Pd–V interdiffusion and high susceptibility to oxidation as shown through microscopy and compositional analysis. The Pd/Ta membranes were the most resilient to oxygen, but their mechanical integrity was relatively poor and they failed within 48 h due to Pd–Ta interdiffusion. In contrast, Pd/Nb membranes exhibited high permeability throughout the 168 h of testing, with no Pd–Nb interdiffusion observed. The decline in permeability observed during testing was attributed to partial Pd delamination as a result of membrane deformation. These results provide pathways for further development of these membranes.