Adsorption of CO2 on N-doped carbon materials: the effect of the subsurface layer

Abstract

In this work, density functional theory (DFT) was employed to study CO₂ adsorption on graphite sheets with different types of nitrogen-containing adsorption sites: graphitic-N, pyrrolic-N, pyridinic-N. A periodic graphite model consisting of two layers was used in this study, and many-body dispersion (MBD) corrections were utilized to accurately account for the interactions between the graphite layers and the CO₂ molecule. For the first time, the effect of the subsurface graphite layer on the CO₂ adsorption properties of nitrogen-doped carbon materials was investigated. It was shown that the substitution of carbon atoms with nitrogen results in a redistribution of the electron density between the surface and the subsurface layer, especially in the presence of a carbon vacancy. The electron density redistribution on the graphite surface has a significant impact on CO₂ adsorption energy, the distance between the surface and the adsorbate molecule, and the geometry of CO₂ during its interaction with the graphite layer. CO₂ adsorption energy was found to increase in comparison to that on pristine graphite in the case of carbon materials containing one graphitic-N site or pyridinic-N sites with a varying (1–3) number of nitrogen atoms, allowing the regulation of adsorption properties.