First-principles evaluation of Pd–Pt–Ag and Pd–Pt–Au ternary alloys as high performance membranes for hydrogen separation

Abstract

Membrane technologies are considered as a promising candidate for high purity hydrogen separation. Ternary alloys membranes show high permeance, high purity quality and good stability for separation of hydrogen, while the relational separation mechanism at atomic scale is still unclear for the most of ternary alloys. In current work, molecular dynamics (MD) and first-principles simulation are applied to predict H2 separations performances of Pd–Pt–Au and Pd–Pt–Ag membranes from CH4, CO, N2, CO2, H2S and H2O mixed gases. The separation properties of the alloys are evaluated by permeability and selectivity of various gases, and the performance of Pd–Pt–Ag and Pd–Pt–Au three-phase membranes are compared to those of Pd–Pt alloy. Our calculations indicate that Pd–Pt–Au alloy present superior selectivities of 3.6 × 1047, 1.1 × 1028, 3.7 × 1011, 4.9 × 1018, 2.2 × 1010, 1.1 × 106 for H2/CO, H2/CO2, H2/CH4, H2/N2, H2/H2S, H2/H2O, respectively, and a permeability of 1.24 × 10−1mols−1m−2pa−1 toward separation of hydrogen from the gases mixture, which is accorded to experimental conclusions. H2 permeance of the alloys exceeds industrial production limit from 100 to 600 K, while other impurity gases do not reach the permeability limits of industrial production even at high temperatures of 600 K.