Effects of quadrupole moments of graphite surface on adsorption of simple gases on graphitized thermal carbon black

Abstract

The quadrupole moment of carbon atoms in the graphite layer has a surface mediation effect on the adsorption of simple gases on graphitized thermal carbon black. Basically, the graphite surface exerts an electric field in the volume space above the surface, inducing a dipole moment on every particle above the surface. The dipole moment in each particle is modelled with the Drude oscillator model. Because of polarization, the dipole–dipole interaction gives lower intermolecular potential energy between adsorbed particles. As a result the adsorption isotherm in the region where monolayer is being completed is lower than that if this effect of induced dipole is neglected. This phenomenon of reduction in the intermolecular interaction has been tested against the experimental data of argon on graphitized thermal carbon black, and the agreement between our model and the data is excellent. We also tested the surface defect (geometrical factor) as a possible reason for surface mediation, but the results fail to agree with experimental data, lending support to the possibility of surface electric effect as the principal reason for the surface mediation.