Adsorption of CH4 on nitrogen- and boron-containing carbon models of coal predicted by density-functional theory

Three adsorption sites were taken into account for 5 × 5 × 1 graphenes, namely, Top, Bond and Center. The dotted line circle indicates the carbon atoms of graphene doped by nitrogen and/or boron. Three adsorption orientations of methane, including Down, Up and Parallel configurations.