The collision, adsorption, desorption, and diffusion of methane on two isomers of graphite carbon nitride (g-C3N4) (heptazine and s-triazine) were investigated using Monte Carlo (MC) and molecular dynamics (MD) simulation. The Langmuir parameters qm & b and the heat of adsorption for heptazine isomer are higher than the s-triazine isomer of the g-C3N4 surface, which shows a higher capacity of methane adsorption and higher interaction of heptazine isomer with methane molecules. The ratio of adsorption rate to the rate of desorption (rads/rdes) of methane for heptazine isomer is higher than s-triazine isomer and decreased by increasing the bulk gas phase pressure for both isomers, but the decreasing rate for s-triazine isomer is higher than heptazine isomer of the g-C3N4 surface. The volume cell and density cell of heptazine isomer than s-triazine isomer increased the higher uptake of methane. Also, the more nitrogen atoms in the heptazine act as active sites for higher adsorption. The calculated diffusion coefficient for s-triazine and heptazine in 298 K were 9.98 × 10–4 cm2/s and 3.96 × 10–4 cm2/s, respectively. The heptazine isomer displayed higher adsorption energy and lower diffusion of methane than the s-triazine isomer.

Keywords