Unveiling the hydroxyl-dependent viscosity of water in graphene oxide nanochannels via molecular dynamics simulations

Highlights: • Distinctive viscosity of water in GO nanochannels is unveiled and predicted. • Water viscosity is obviously anisotropic and has a nonmonotonic variation. • Van der Waals force, hydrogen bond and layered structure are coupled together. • Eyring's theory is effective to predict the average viscosity to some extent. We present a molecular dynamics study on the viscosity of water confined in graphene oxide (GO) nanochannels, with a major consideration of its dependence on the density of hydroxyl groups on GO sheets. The results show that the anisotropic water viscosity exhibits a nonmonotonic variation with the density of hydroxyl groups, owing to the coupling interactions between water molecules and GO sheets and their relating momentum dissipation among water molecules within water layers, viscous friction among water layers. The calculated viscosity is consistent with the experimentally and numerically reported water viscosity in literature and the Eyring's absolute action theory.