Molecular-Level Understanding of the Effect of Water on Oil Transport in Graphene Nanochannels

In this study, we used nonequilibrium molecular dynamics (NEMD) simulation to study the pressure-driven flow of oil in surface-functionalized graphene channels. We found that oil transport velocity could be improved by introducing water into the channel. Further study reveals two possible different mechanisms for the increased transport velocity of the water-oil system: On the one hand, the water film is formed between the oil and graphene substrates under driving force, which blocks the significant intermolecular interaction between the graphene layers and the oil molecules; on the other hand, the apparent viscosity of the liquid mixture is reduced by introducing water in the channel, which improves the efficiency of transport. Further comparative analysis on surfaces with different functional groups and oil with different polarities proves the universality of this water-induced flow transport enhancement of oil. The results may be useful for optimizing existing oil recovery devices to improve oil transport efficiencies.