Electronic structure modelling of the edge-functionalisation of graphene by MnO particles

The use of graphenic carbon is attractive as a basal or intermediate support for catalytic particles in advanced catalytic electrodes. This popularity is motivated by its excellent electrical properties and ability to form foliated conformal coatings of exceptional surface area and flexibility. Surface- and edge-functionalisation of graphene sheets affords diverse routes to the covalent attachment of candidate catalytic species. Of particular interest to advanced water oxidation is the possibility of covalent attachment of MnxOy species partially recapitulating the chemistry of the Mn4O5Ca active site of Photosystem II (PSII), which achieves the four-electron oxidation of water under physiological conditions. Here, we report aperiodic density functional theory (DFT) investigations of candidate attachment geometries for a variety of manganese oxide particles to graphene sheets. We find that the flexibility of graphene sheets as well as the conformational degrees of freedom of candidate edge functionalisation permits a large variety of realistic attachment geometries that can act as attachment sites for molecular manganese-oxide species or nuclei for the growth of periodic manganese oxides. We find that substantially simplified models of graphene attachment afford an excellent compromise between computational efficiency, tractability, and accuracy, and characterise the accuracy of these models in detail.