Impact of high adsorbent conductivity on adsorption of polar molecules: simulation of phenol adsorption on graphene sheets

Abstract

The high conductivity of nanoprous carbons has a significant effect on adsorption of polar molecules; however, the mechanisms underlying this effect are not well-understood, and this effect is generally not considered in adsorption modeling. To investigate the impact of high host conductivity on the adsorption properties of vertical stacks of the graphene sheet, phenol vapor has been chosen as a simple polar adsorptive for our case studies. The influence of high surface conductivity of graphene is taken into account during Grand Canonical Monte Carlo (GCMC) simulations by considering the resulting image charges, and using the corresponding analytical solution to compute the electrostatic energy of the polar molecules confined between two infinite parallel conducting planes. We find that the consideration of the high conductivity affects the atomic configuration of the adsorbed molecules, based on our results for two different pore widths of 1 nm and 0.65 nm. Allowing for the high conductivity results in more stable energy levels, greater heat of adsorption and smaller distances between phenol molecules and the graphene sheet. There results are shown to be in accord with electronic density functional theory calculations, and literature experimental data. The contributions of different guest–guest (phenol–phenol) and guest-host (phenol and graphene) interactions between molecules are studied.