Effect of alloying elements on hydrogen absorption properties of palladium-based solid solution alloys

The hydrogen absorption energy and the density of states (DOS) are calculated based on the density functional theory to study the effect of alloying elements on the properties of Pd-M solid solution alloys (M = Rh, Pd, Ag, Ir, Pt, Au). The calculated H absorption energy shows a dependence on the identity of the alloying elements and the trend indicates a correlation with experimental result. The calculation results suggest that the local environment surrounding the H atoms strongly affects the H absorption energy. That is, the first nearest-neighbors of the H atom determine the stability of the system and this implies that H absorption capacity of the entire alloys attributes to the atomic-scale configurations. The DOS provides a good explanation of these observations. Hybridization between the nearest-neighbor metals and H shows evidence of the contribution of the local environment. Furthermore, the elemental dependence of the H absorption energy for each alloy is explained by the DOS near the Fermi energy, which is found to influence the stability of H absorption.