Advancing Tribological Understanding: Insights into In-Plane Wear and Edge Friction Mechanisms of Graphene and Its Derivatives

Friction and wear play pivotal roles in dissipating mechanical energy in engineering systems, contributing significantly to global energy consumption. Two-dimensional materials, such as graphene, exhibit exceptional microscale friction and wear resistance, making them promising candidates for advanced lubrication. However, their macroscopic performance faces challenges, limiting widespread industrial application. This paper reviews our recent investigations into the tribological properties of graphene and its derivatives using atomic force microscopy (AFM) experiments, density functional theory (DFT), and molecular dynamics (MD) simulations. We found a competitive interplay between interfacial interactions and stiffness that influences wear resistance. The interaction between two-dimensional materials and substrates, resembling a spring-like mechanism, further complicates the wear process. Moreover, examining graphene step friction reveals that edge characteristics significantly affect friction force, with zigzag (ZZ) edges exhibiting higher friction than armchair (AC) edges. MD simulations demonstrate that ZZ edges form more resistant chemical bonds during sliding, intensifying morphological effects. To address these edge wear challenges, a scanning probe mechanochemical etching method is proposed for graphene edge engineering. Controllable and low-damage processing generates well-defined nanostructures, overcoming limitations of traditional methods. Wear rate analysis and DFT calculation reveal the atom-by-atom removal mechanism during active tip etching, elucidating the mechanochemical process. These studies offer insights into the cross-scale lubrication mechanism of two-dimensional materials, providing valuable strategies for the fabrication of ultrathin lubricating coatings.