TCNE-modified graphene as an adsorbent for N₂O molecule: a DFT study

Adsorption behavior of nitrous oxide (N₂O) on pristine graphene (PG) and tetracyanoethylene (TCNE) modified PG surfaces is investigated using density functional theory. A number of initial adsorbate geometries are considered on both surfaces and the most stable ones are chosen upon calculation of the adsorption energies (E_ads). N₂O is found to adsorb in a weakly exoergic process (E_ads ∼ -3.18 kJ mol^-1) at the equilibrium distance of 3.52 Å on the PG surface. N₂O adsorption can be greatly enhanced with the presence of a TCNE molecule (E_ads = -87.00 kJ mol^-1). Mulliken charge analysis confirms that adsorption of N₂O is not accompanied by distinct charge transfer from the surfaces to the molecule (˂ 0.001 │e│ for each case). Moreover, on the basis of calculated changes in the HOMO/LUMO energy gap, it is found that electronic properties of PG and TCNE modified PG are not sensitive toward adsorption of N₂O, indicating that both surfaces are not good enough to introduce as an N₂O detector. However, the considerable amount of E_ads in TCNE modified PG can be a guide to the design of graphene-based adsorbents for N₂O capture.