Hydrogen Chemisorption on Pd-Doped Copper Clusters

The structural evolution, electronic, and magnetic properties of Pd-doped Cu n ( n = 1–12) clusters and the dissociative chemisorption of H 2 on the lowest energy structures are investigated on the basis of density functional theory. The Pd impurity occupies the surface site and changes the geometry of the pure copper clusters; i.e., a transition from 2D to 3D occurs at n = 5. The relative stability and chemical activity of the minimum energy structures are analyzed through the binding energy per atom, second-order energy difference, and energy gap. The results show that the stability of Cu n Pd containing an even number of Cu atoms is higher than that of Cu n +1, which is related to the closed-shell electronic structure. The electronic properties such as the ionization potential and electron affinity are calculated for Cu n Pd and Cu n +1 and compared with experimental data available. By studying the H 2 chemisorption on the Pd-doped Cu n clusters, the results show that the doped clusters possess similar interactions with atomic H compared to the pure ones. Interestingly, the hydrogen dissociation pathway on Cu n Pd clusters shows that certain clusters possess significantly lower activation barriers than the pure ones. For Cu 4–6 Pd, the energy barriers for the release of chemisorbed hydrogen range from 0.63 to 0.75 eV, while from 1.19 to 2.53 eV on Cu 5–7, suggesting that the doped clusters are more suitable for H 2 dissociation and utilization. These results can be understood in terms of the localization of the spin-polarization density.