Asymmetric Quantum Pd Films for Enhanced Hydrogen Separation

Based on density functional theory calculations and numerical simulations, we have investigated the permeation of H2 through ultra-thin Pd quantum films. The H2 flux can be highly increased by the elevation of the chemisorption-well on the permeate side without significantly blocking the subsurface-surface penetration. We find that Cu-coated asymmetric Pd quantum films (with the Cu monolayer on the permeate side) will enhance the capability for H2 separation: the recombination barrier for H is reduced from 1.36 to 0.79 eV, while the subsurface-surface penetration barrier is only slightly increased from 0.04 to 0.10 eV. Numerical simulations show enhanced H2 flux by 5 orders of magnitude as an upper-limit for asymmetric Pd films over symmetric ones under similar conditions.