Density Functional Theory Study of the Organic Functionalization of Hydrogenated Graphene

Graphene is a carbon nanomaterial formed by planar hexagonal structures, with striking properties and promising potential applications that already have attracted worldwide attention. In this work, we present density functional theory calculations of the organic functionalization of hydrogen terminated graphene with acetylene, ethylene, and styrene through a radical initiated reaction. We have optimized the atomic structure for different stages of the reaction with and without van der Waals dispersion forces. It is found that although the differences between the final and intermediate states in all three cases do not change significantly, the binding energies, which are more negative with the dispersion forces, may favor the completion of the reaction. For acetylene and ethylene, we have also calculated the minimum energy path from the metastable to the stable state with and without van der Waals interactions. The results are compared with previous works of similar adsorption processes on hydrogen terminated silicene and silicon [111] surfaces, indicating that the hydrogenated graphene system is more difficult to be functionalized with organic molecules than the other surfaces due to its rather small carbon lattice structure and higher electronegativity of carbon atoms with respect to silicon atoms