First-principles screening of PdCuAg ternary alloys as H2 purification membranes

Predictions based on Density Functional Theory (DFT) calculations have proven to be a useful complement to experimental efforts to characterize permeation of hydrogen through metal membranes at elevated temperatures. Previous applications of this approach have focused on relatively small numbers of alloys with specific binary or ternary compositions. We describe DFT-based calculations that provide predictions for the solubility, diffusivity, and permeability of hydrogen at elevated temperatures in PdCuAg alloys for a wide range of compositions of this ternary alloy that yield substitutionally disordered fcc materials. Our results show that the variation in permeability of hydrogen among these alloys is more closely tied to variations in solubility than variations in diffusivity. These results give a detailed description of a ternary alloy of practical interest for high temperature H2 purification and also demonstrate a general strategy for making predictions about complex metal alloys for this application.