Interaction energies, structure, and dynamics at functionalized graphitic structure–liquid phase interfaces in an aqueous calcium sulfate solution by molecular dynamics simulation

Molecular dynamics simulations were performed to study the effect of surface functionalization of graphitic structures on the molecular-scale energetic, structure, and dynamics of water and ions at graphite surface–liquid phase interfaces. Three types of carbon surface structures were investigated: a pristine graphite plane and two graphite planes functionalized with hydroxyl (–OH) and carboxylate (–COO−, deprotonated carboxyl) groups. A divalent salt, calcium sulfate, was combined with water to simulate an electrolyte liquid phase. Results highlighted the ordering of H2O molecules that occurs near graphite surfaces and revealed a subtle effect on the position of the H2O layers associated with ions and functional group type. Surface functionalization of the graphitic structures affected the H-bond network and the orientation of near-surface H2O molecules, decreased the ion hydration, and significantly restrained the mobility of near-surface H2O molecules and bulk Ca2+ and SO42- ions.