Tribochemistry of graphene on iron and its possible role in lubrication of steel

TL;DR

This paper investigates how graphene acts as a lubricant on iron surfaces by analyzing its tribochemical interactions, revealing that graphene passivates iron surfaces and reduces friction through electronic and surface energy effects.

Contribution

It provides a first-principles analysis of graphene's tribochemical effects on iron, linking electronic properties to lubrication performance.

Findings

Graphene strongly binds to iron surfaces, reducing surface energy.

Graphene-coated surfaces become inert with low adhesion and shear strength.

Electronic properties of interfaces are key to understanding friction reduction.

Abstract

Recent tribological experiments revealed that graphene is able to lubricate macroscale steel-on-steel sliding contacts very effectively both in dry and humid conditions. This effect has been attributed to a mechanical action of graphene related to its load-carrying capacity. Here we provide further insight into the functionality of graphene as lubricant by analysing its tribochemical action. By means of first principles calculations we show that graphene binds strongly to native iron surfaces highly reducing their surface energy. Thanks to a passivating effect, the metal surfaces coated by graphene become almost inert and present very low adhesion and shear strength when mated in a sliding contact. We generalize the result by establishing a connection between the tribological and the electronic properties of interfaces, which is relevant to understand the fundamental nature of frictional forces.