Computational Studies on a Palladium Atom Adsorption on the Surface of Edge-Modified Nanographenes

A key application of graphitic materials is to utilize their vast graphitic surfaces to anchor metal nanoparticles (NPs). A question arises about where metal NPs prefer to adsorb on these carbon sheets. This prompted us to perform density functional theory (DFT) calculations on Pd-nanographene (NG) complexes. This NG features a fully benzenoid structure with 174 carbon atoms and bears N-methyl five-membered imide rings at the edges. It serves as a model for Pd-NP-lipophilic NG composite materials. A single Pd atom was used in the calculations due to limited computational resources. The DFT calculations with or without the polarizable continuum model of THF showed that the Pd atom prefers to adsorb at the edge. An epoxy group, which models an oxidized graphitic surface, also attracts the Pd atom but less selectively than at the edge. On the other hand, no selectivity was found on the graphitic surface because the binding energy is quite similar across the graphitic surface. Based on these calculations, in situ-generated Pd atoms in THF could mainly adsorb at the edges, also attach around oxidized groups on the surface when they exist, and ultimately bind to the graphitic surface.