DFT Study on the Interaction of Subnanometer Cobalt Clusters with Pristine/Defective Graphene

The cobalt nanoparticles deposited on graphene are new interesting catalytic systems for Fischer-Tropsch synthesis (FTS) to obtain clean fuel hydrocarbons. Especially, graphene doped with Co nanoparticles could be a nice alternative material for catalysis in CO + H-2 reaction. On the basis of first-principles calculation, we have analyzed the binding of Co-n clusters (n = 17) with pristine (PGr) and defective graphene (DGr). Our analysis shows that the electronic structure of the graphene-supported Co subnano-clusters plays a significant role in the catalytic activity owing to metal-support interactions, and the interaction between the Co-n clusters and the graphene is local. Our results also show that the bigger the size of Co-n clusters is, the smaller the interaction between the cluster and the support is, and the lower its structural distortion is. In addition, the nucleation of Co-n clusters on PGr is thermodynamically favorable, but the opposite trend is obtained for DGr. Both the pristine and defective surfaces facilitate agglomeration of Co-6 cluster, implying that the graphene support remarkably promotes and even prevents the sintering process of the small Co clusters. The Bader charge analysis shows that both the cobalt and graphene support are responsible for the charge densities of Co clusters.