DFT investigation of the reactivity of graphene supported on Au(111), Cu(111) and MoS2. Patricia

P. PAREDES OLIVERA; F. A. SORIA; E. M. PATRITO

Lille

Congreso; European Materials Research Society Spring Meeting,; 2015

European Materials Research Society

As graphene comprises only a single atomic layer, its reactivity can be influenced by the underlying substrate. As test reactions, we considered the formation of epoxi groups on graphene from molecular O2 and atomic O reactants. Density functional theory calculations (DFT) including van der Waals interactions were performed to calculate the energy profiles along the reaction coordinate. The activation energy barrier was the parameter chosen to investigate the effect of the substrate on the reactivity of graphene. In the case of gold, we also considered surfaces with gold adatoms and alkanethiols (propanethiol and 2-aminoethanethiol). The formation of an epoxi group from atomic oxygen occurs in single elementary step whereas in the case of molecular O2 the reaction occurs in two steps corresponding to the breakage of each of the two bonds of the oxygen molecule: in the first step an intermediate is formed after the breakage of the first O-O bond and the formation of the corresponding C-O bonds. In the next step the remaining O-O bond is broken and the O atoms diffuse to form two methoxy groups. The general trend is a decrease of activation energy barriers as compared to free graphene, whereas in the case of thiolated gold there is no major influence, indicating that the electronic structure of graphene is not altered. The reaction of O2 has energy barriers of 2.64 and 0.70 eV for both elementary steps on free graphene. When it is adsorbed on Au(111), the barriers decrease to 2.12 and 0.55 eV, respectively. The differences in reactivity are interpreted in terms of density of states analysis and electron density difference plots.