Synergistic lubrication enhancement by load-driven edge self-passivation and structural heterogeneity in graphene/MoS₂ coatings

Abstract

Graphene/MoS₂ heterostructure coatings are promising solid lubricants due to their intrinsic lattice mismatch and weak van der Waals forces between chemically inert atomic layers. However, macroscale lubrication enhancement remains limited due to the competitive effect between in-plane edge interactions and incommensurability. Herein, graphene/MoS₂ heterostructure coatings with controlled heterogeneity are fabricated in situ by magnetron sputtering method. The graphene/MoS₂ heterostructure coating outperform its individual components in friction properties due to the synergistic integration of the chemical stability of graphene and the load-bearing capacity of MoS₂. Experiments and molecular dynamics simulations reveal that increased structural heterogeneity intensifies interfacial edge interactions, initially promoting structural disorder and frictional energy dissipation. Additionally, a load-driven self-passivation mechanism is uncovered to saturate dangling bonds and repair structural defects, consequently forming a robust passivated interface that facilitates smooth and well-ordered shear sliding. As a result of the synergistic interplay between load-driven edge self-passivation and structural heterogeneity, the highly heterogeneous graphene/MoS₂ coating exhibits a 3-fold friction reduction and 12-fold wear reduction under high-load compared to low-load conditions. The results reveal a novel synergistic lubrication mechanism enabled by structural heterogeneity and load-driven interfacial engineering and offer insights into how to transform conventionally undesirable structural disorder into significant lubrication enhancements.