Adsorption in micro and mesoporous slit carbons with oxygen surface functionalities

Microscopic surface heterogeneity has in general significant effects on the overall adsorption characteristics of porous solids. However these effects may differ to a large extent when different adsorbates are used. Here, we present and compare simulations of N-2 and CO2 adsorption in slit shaped pore models having a graphitic surface with oxygen functionalities. We use models with three different degrees of oxidation, to study the impact of the surface oxygen content on gas adsorption in both micro- and small mesopores. Significant contribution on the energies and densities stems from the electrostatic interactions used in the solid fluid force fields. Therefore adsorption is strongly influenced by the presence of partial charges on surface sites and functional groups. By using CO2 instead of N-2 we get a clearer picture of the surface energetic details, as revealed on the computed isotherms and on the isosteric heats of adsorption. CO2 adsorption can be used as a complementary tool to N-2 porosimetry, for the surface chemistry characterization of carbon solids. (C) 2014 Elsevier Inc. All rights reserved.