Advances in hydrogen selective membranes based on palladium ternary alloys

Abstract

Hydrogen containing a minimum amount of contaminants is required for its application in fuel-cell technology. For this purpose, palladium and palladium binary alloy membranes have been widely studied in the last decades due to their ability to selectively permeate hydrogen. The scope of this review is to provide an in-depth analysis of the research on Pd-based ternary alloys and their application as hydrogen separation membranes with a special focus on the PdAgAu, PdCuAg, and PdCuAu systems. The combination of these particular elements - Cu, Au, Ag - can improve hydrogen permeability and chemical resistance. Correlations between structural, surface and permeation properties of the ternary alloys under pure hydrogen and gas mixtures are extensively discussed. A general correlation between hydrogen permeability and the lattice parameter is proposed. In particular, the surface segregation behavior is analyzed for these ternary alloys even after being exposed to CO, CO2, and H2S. Further research is needed to develop membranes with improved long-term stability.