Effects of functional group concentration, type, and configuration on their saturation of methanol adsorption on functionalized graphite

Abstract

Adsorption of methanol on functionalized graphite at 298 K was studied using a grand canonical Monte Carlo simulation to investigate the effects of functional group (Fn) properties, such as concentration, type, and configuration, on their saturation. It was found that the initial methanol molecule was adsorbed on the strongest active site of the functional groups with multiple hydrogen bonds. The additional methanol molecules were then adsorbed on the weaker active sites until they became saturated. Once the Fns were saturated, the adsorption processes were followed by monolayer and multilayer processes, and they were no longer influenced by Fn properties when the loading increased. In this work, we determined the effects of surface chemistry properties on their saturation state by the following: (1) The difference in Fn concentration is insufficiently influenced on the value and trend of the isosteric heat along the loading; the only difference is that the higher concentration causes the isosteric heat to shift to higher loadings. (2) The Fn type and configuration are affected on both value and trend of the isosteric heat. Heat contributions (fluid–fluid, fluid–functional group, and fluid–graphene basal plane), snapshots, local densities, and orientation distributions are discussed in this work.