Adsorption of metal adatom on nanographene: Computational investigations

Recently synthesized nanographene, which is a discrete fragment of graphene, is considered a new form of carbon. We perform density functional theory calculations on the adsorption of various metal adatoms on the saddle-shaped nanographene tetrabenzo[8]circulene (TB8C) and its modified derivates. Our results show that nanographene is better than pristine graphene in adsorbing metal adatoms. Octaamino-tetrabenzo[8]circulene (OA-TB8C) shows the best adsorption capability among the TB8C derivates. Bonding analysis on the metal@nanographene complexes reveals different bonding types for different metal elements. We find that metal adatoms that form ionic bonds or partially covalent bonds with the nanographene have adsorption energies on OA-TB8C that are mostly higher than or close to their own cohesive energies. The saddle geometry of nanographene enables them to adsorb two metal adatoms at the same time, especially for alkali metal atoms.