Towards Water-based superlubricity by charged graphene surface in the boundary lubrication regime

ZC Wang and DS Mao and YF Yu and H Li and YG Yan and W Zhang and JJ Lu and SF Xu and JQ Shi, SURFACES AND INTERFACES, 72, 106957 (2025).

DOI: 10.1016/j.surfin.2025.106957

A new model of graphene friction pair consisting of charged and uncharged surfaces was proposed to achieve water-based superlubricity in the boundary lubrication regime, and molecular dynamics (MD) simulations were performed to reveal superlubricity mechanisms. It is found that the new model of graphene friction pair can significantly reduce the friction coefficient by two orders of magnitude to 10e-3 and thus achieves superlubricity for water as a lubricant. The existence of slip plane between the uncharged graphene substrate and water molecules due to the disappearance of pi-H bonds contributes low friction. In addition, fluidity of hydration layers induced by the charged graphene and low energy dissipation due to hydrogen bonding forces also contribute superlubricity. An optimal value of surface charge exists for achieving superlubricity with the minimum friction coefficient. Effects of ion concentration (NaCl) on superlubrication were also studied. The friction coefficient decreases with the increase of ion concentration. The electrostatic force induced by the charged graphene and salt solution can form a state of electrostatic suspension under a large normal load, and the smooth hydration layer can result in a smaller energy barrier to reducing friction. The current study provides a new vision for hydrated boundary superlubrication.

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