A Density Functional Theory Study of Palladium Nanoparticles and Their Redox Properties on Graphene

Nanoparticles exhibit characteristics that are different from bulk materials as well as from atoms resulting in their application in numerous fields of applied material science. In particular, small palladium nanoparticles supported on graphene have been found to be outstanding catalysts for the Suzuki cross-coupling reaction. One explanation as to why these supported nanoparticles are such outstanding catalysts is because they may act as both electron donors and acceptors. Charge donating ligands are known to lower the ionization energy of clusters, making the clusters better donors. In this project, it is hypothesized that graphene supports may also act like charge donating ligands, lowering the ionization energy and making the supported catalyst a better charge donor. To understand this hypothesis we investigate the structure, and energetics of small Palladium (Pd) clusters of 1-7 and 13 atoms as free clusters, and on different graphene-based supports using gradient-corrected density functional theory. Graphene is found to increases the stability of the supported clusters and we find that graphene also significantly reduces the ionization energy of the palladium clusters, which is consistent with the hypothesis that graphene is a good support for catalytic processes in part because it makes the cluster a better charge donor