Reducing Properties of Superalkalis on Pyridinic Graphene Surfaces: a Computational Study

Abstract

The hyperlithiated species ${\mathrm{Li}}_{k+1}{F}_k$ (k=1, 2, 3, and 4) have been studied by quantum mechanical (QM) methods. Different structures have been localized for each molecule by the CBS-QB3 composite method: all the isomers show superalkali properties and strong tendency to donate an electron to carbon dioxide forming stable ${\mathrm{Li}}_{k+1}{F}_k···{\mathrm{CO}}_2$ complexes. With the aim to find molecular systems able to stabilize superalkalis, geometries of complexes between superalkalis and pyridine and superalkalis and graphene surfaces doped with a pyridinic vacancy were calculated. The pyridinic graphene sheets were modeled with two finite molecular systems C₆₉ H₂₁ N₃ and C₁₁₇ H₂₇ N₃ . The interaction with one pyridine molecule is quite weak and the superalkali maintains its structure and electron properties. The affinity for graphene sheets is instead stronger and the superalkalis tend to deform their geometry to better interact with the graphene surface. However, the superalkalis continue to show the tendency to transfer electrons to carbon dioxide reducing CO₂ , as found in graphene absence.