A DFT study of the adsorption of deep eutectic solvents onto graphene and defective graphene nanoflakes

The interaction of four deep choline chloride-derived eutectic solvents (DESs) with both graphene nanoflakes (GNF) and its defective double-vacancy and Stone-Wales forms (DV-GNF and SW-GNF), was evaluated using density functional theory (DFT). The presence of defects increases the adsorption energy of DESs, following the order DESnDV-GNF > DESnSW-GNF > DESnGNF. Non-covalent interaction and energy decomposition analyses show that the interactions are noncovalent and dominated by dispersive forces. Furthermore, we find that the presence of aromatic moieties in the DESs increases the van der Waals interactions with the surfaces. These interactions decrease the HOMO-LUMO (E-g) energy gap of the surfaces and thus increase reactivity. Reactivity parameter calculations indicate that the chemical potential (mu) and chemical hardness (eta) of the complexes follow the order DESn GNF > DESnSW-GNF > DESnDV-GNF. This order is reversed for the global softness (S) and electrophilicity index (omega). Time-dependent DFT (TD-DFT) calculations predict that the adsorption of DESs onto DV-GNF and SW-GNF should red shift absorption, while the absorption spectrum of GNF surface remains unchanged upon DES adsorption. The biggest changes in the absorption spectra are observed upon adsorption of DESs on the DV-GNF surface due to the stronger affinity of the DESs for this surface. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study utilized DFT to evaluate the interaction of four DESs with various forms of graphene nanoflakes, finding that the presence of defects increases adsorption energy and interactions are noncovalent with dispersive forces being dominant. The aromatic moieties in DESs were observed to enhance van der Waals interactions with surfaces.