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

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( *)=1.018E(cal)( *), r(2)=0.964).