Calculations Of Adsorption Energies, Coadsorptions, And Diffusion Barriers Of H Atoms, And The H-2 Formation On A Nanographene Surface (Coronene)

Adsorption and diffusion of ortho, meta, and para cis hydrogen dimers, on central and edge rings of coronene (nanographene), were studied by using the DFT-D method, considering different multiplicities. Calculated values of adsorption energy, coadsorption energy, diffusion barriers, and reaction barriers for the H-2 formation (Langmuir-Hinshelwood (LH) mechanism) were evaluated for ortho and para locations. The adsorption of an H-center dot atom increases the adsorption energy of another hydrogen (coadsorption). The most stable dimers are those where an H-center dot is adsorbed on hydrogenated-edge sites. Dimers with multiplicity M = 1, with H-center dot separated by an odd number of bonds, have higher coadsorption energies (higher diffusion barriers) than those where the separation is by an even number. The H-2 formation is more feasible on edge-edge and edge-center sites; however, on ortho hydrogenated-edge sites, it is not energetically favored. For M = 3, H-2 formation is not observed because desorption of H-center dot occurs.