Predicting, Fabricating, and Permeability Testing of Free-Standing Ternary Palladium−Copper−Gold Membranes for Hydrogen Separation

Abstract

For hydrogen from coal gasification to be used economically, novel separation processes that produce high-purity H2 must be developed. While binary palladium based alloys have shown promising pure hydrogen flux values, the search for optimal binary or ternary alloys is an involved and costly process due to the immense number of alloy variations that can be prepared and tested. In this paper an approach to identify, fabricate, and experimentally verify the hydrogen permeation performance of PdCu and PdAu binary alloys and ternary alloys of PdCuAu at various copper and gold concentrations to produce robust, poison-tolerant, hydrogen selective free-standing membranes is reported. This approach utilizes three primary tasks of (1) materials modeling and composition selection, (2) fabrication of high-performance binary and ternary alloy membranes, and (3) membrane testing and evaluation that are all operating independently and concurrently. For the binary Pd−Cu system, using a pure Pd membrane as the reference, both the theoretically predicted and experimentally measured additions of copper lowered the hydrogen permeability. For the binary Pd−Au system, the addition of gold slightly lowered permeability in the theoretical model but in the experimental testing was enhanced. For the ternary system, both experimental and theoretical permeabilities were depressed, with Cu exhibiting a larger influence on reducing the permeability.