Determining molecule–carbon surface adsorption energies using molecular mechanics and graphene nanostructures

Abstract

Five model surfaces were developed using molecular mechanics with MM2 parameters. A smooth, flat model surface was constructed of three parallel graphene layers where each graphene layer contained 127 interconnected benzene rings. Four rough surfaces were constructed by varying the separation between a pair of graphene nanostructures placed on the topmost layer of graphene. Each nanostructure contained 17 benzene rings arranged in a linear strip. The parallel nanostructures were moved closer together to increase the surface roughness and to enhance the molecule–surface interaction. Experimental adsorption energy values from the temperature variation of second gas–solid virial coefficients values were available for 16 different alkanes, haloalkanes, and ether molecules adsorbed on Carbopack B (Supelco, 100 m 2/g). For each of the five different surface models, sets of 16 calculated adsorption energies, E cal ∗ , were determined and compared to the available experimental adsorption energies, E ∗ . The best linear regression correlation between E ∗ and E cal ∗ was found for a 1.20 nm internuclei separation of the surface nanostructures, and for this surface model the calculated gas–solid interaction energies closely matched the experimental values ( E ∗ = 1.018 E cal ∗ , r 2 = 0.964 ).