Substrate tuning of graphene reactivity

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

Boston, MA

Congreso; 2015 Materials Research Society Fall Meeting & Exhibit.; 2015

Materials Research Soc

The peculiar band structure of graphene allows for it p or n doping depending on the electronic structure of the supporting substrate which may affect the graphene reactivity. In the case of SiO2and Al2O3surfaces, for example, it has been observed (1) that the underlying substrate affects the reactivity of graphene. The use of appropriate substrate patterns with regions with strong and weak coupling with graphene could allow for the selective functionalization of graphene and the development of functionalization patterns.In this work we use Density Functional Theory to evaluate the influence of Au(111), Cu(111) and MoS2 substrates on the reactivity of supported graphene as well as on graphene ribbons. As test reactions we consider the dissociativeadsorption of H2, H2O and O2.As a key parameter in surface reactivity is the activation energy barrier of elementary reaction steps, we performed extensive Nudged Elastic Band calculations to obtain the energy profiles along the reaction coordinate of thedissociative adsorption reactions considered. In all cases the reactivity was compared to that of bare graphene.When graphene is supported on the metal surfaces, the general trend is a decrease of activation energy barriers, being more pronounced on the copper surface. In the case of the dissociative adsorption of O2, the nature of themetal substrate not only affects the energy barriers but also the reaction mechanism. During the course of the reactions, the graphene height above the surface decreases up to 0.5 A in the case of the Cu(111).As an example of the influence of the metal substrate on the graphene reactivity, the energy barriers for the dissociative adsorption of H2 O into adjacent H and OH species are 3.19 eV, 2.83 eV and 2.44 eV on bare graphene,graphene on Au(111) and graphene on Cu(111), respectively. The influence of the MoS2 substrate is less pronounced. The observed differences in reactivities are correlated to the charge transfer processes which occur during the course of the reactions.In the case of supported graphene nanoribbons, we focused on the reactivity of the edges.(1) Q. H. Wang et al. Nat. Chem., 2012, 4, 724