The macroscale low-friction performance of FGO-CMMCs and GO-CMMCs is driven by the sliding interface between the graphene-copper tribofilm and the steel counterface, but low-friction lifetimes and antiwear performances are influenced by the formation of a robust fluorine-rich transfer layer on the counterface. Graphene is known to not easily form a tribolayer onto steel surfaces due to its chemical inertness. Conversely, the oxygenfunctional groups on graphene oxide are susceptible to adhesion onto metal surfaces, as well as inhibiting low-shear interactions between nanosheets, therefore, accelerating damage of the nanosheets under sliding. Liu et al. recently demonstrated that sliding fluorographene oxide coatings on steel generates a metal-fluoride surface on the steel counterface, promoting a robust transfer film that facilitates a low-shear sliding mechanism between steel contact pairs. However, due to the nature of the contact pair in FGO-CMMC sliding, there is no evidence of carbon on the transfer film, suggesting that the tribofilm structure is asymmetric: