Theoretical Study of Palladium Cluster Structures on Carbonaceous Supports

DFT calculations have been performed on a palladium cluster adsorbed on two different carbonaceous supports, namely, two stacked polycircumcoronene units mimicking a double layer of graphite and a portion of an armchair (6,6) carbon nanotube. All of the systems have been subjected to geometry optimization and electronic structure investigation. This work, which is part of an extensive computational study on heterogeneous catalytic systems, is devoted to identify electronic and geometrical changes in which metal clusters and supports are involved upon interaction. Such analysis is helpful in designing new heterogeneous metallic catalysts, namely, new metal-supported carbonaceous catalysts. Calculations reveal a major geometrical distortion occurring in the palladium cluster supported on both graphite and nanotubes, which is caused by strong Pd−C interactions. The curvature of the nanotube surface seems to provide the basis for a stronger interaction with respect to the flat surface of graphite. This evidence is also pointed out by the atomic orbital overlap occurring between the cluster and the nanotube, as revealed by the density of states analysis.