First-Principles Investigation of C$_{60}$-Pd Interface

Conductivity and hybridization of C$_{60}$-Pd nano-system have been investigated using density functional calculations. From analysis of geometry, energetics and electronic structures, the interaction of C$_{60}$ mono-layer and Pd clusters gives rise to electronic charge transfer at the interface and facilitates the dissociation and uptake of hydrogen, which lead to hydrogen storage. The first-principles studies are carried out by self-consistent plane-wave method. The interaction between ions and electrons is described by projector-augmented wave (PAW) approach. In our calculations, the C$_{60}$ monolayer is doped by the Pd$_{n}$ atoms on $h$-BN with $n$ = 1-4 and 15, but it also forms a metal-C$_{60}$ nano-array with the Pd clusters. Charge transfer occurs at the interface, from the Pd atoms towards the C$_{60}$ monolayer. This electronic property strongly depends on the nature and number of metal atoms. A large amount of charge transfer between the Pd atoms and the C$_{60}$ monolayer indicates a strong interaction under the ionic effect, in contrast with the interaction of the C$_{60}$ monolayer and a metallic surface. The $h$-BN surface merely gains 0.1 electrons via C$_{60}$, proving that $h$-BN is an insulating material. We also find that Pd is a good catalyst for dissociation and storage of hydrogen on the C$_{60}$ molecules. Hydrogen is sufficiently dissociated in the presence of the Pd atoms/clusters, which assists in bonding of the individual H atoms to C$_{60}$. Dehydrogenation of C$_{60}$H$_{x}$ is also discussed in energetics.