Calculations of adsorption energies, coadsorptions, and diffusion barriers of H atoms, and the H₂ formation on a nanographene surface (coronene)

Abstract

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 H2 formation (Langmuir‐Hinshelwood (LH) mechanism) were evaluated for ortho and para locations. The adsorption of an •H atom increases the adsorption energy of another hydrogen (coadsorption). The most stable dimers are those where an •H is adsorbed on hydrogenated‐edge sites. Dimers with multiplicity M = 1, with •H 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 H2 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, H2 formation is not observed because desorption of •H occurs.

Hydrogen Physisorption on BNC Heterostructures: A Systematic Theoretical Study

“…PBE has been shown to be a very reliable density functional that suits well for adsorption studies [21,[30][31][32]. A coronene (C24H12) molecule was chosen as a graphene sheet model, which was successfully involved in our previous papers [21,31] and elsewhere [22,33]. Many works considered a coronene-based model as a minimal model which preserves the properties of graphene [34,35].…”