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 (Eads). N2O is found to adsorb in a weakly exoergic process (Eads ∼ −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 (Eads = −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 Eads in TCNE modified PG can be a guide to the design of graphene-based adsorbents for N2O capture.