Functionalized Graphene from Electrochemical Exfoliation of Graphite toward Improving Lubrication Function of Base Oil

Electrochemical exfoliation of graphene is an environmentally friendly method, which enables mass production. Herein, three ionic liquids (ILs) with the same imidazole cation were used to exfoliate graphite into functionalized graphene, as a lubricant additive in an acetonitrile solution. Chemical and structural characterization revealed the relationship between the functionalization density of graphene and the concentration of IL, showing higher concentrations with higher densities. The exfoliated graphene hybrid oil displayed good dispersion because of a high functionalization density. More importantly, the different anions affected the tribological properties of the exfoliated graphene. Among them, the exfoliated graphene with 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) possessed the best tribological performance, and the average friction coefficient and wear volume were reduced by 32% and 39%, respectively. Through the characterization of worn surfaces and wear debris, the lubrication mechanism and structural evolution of the functionalized graphene were illustrated in detail. The good lubrication function was attributed to the formation of a tribo-film and the disorder transformation of the graphene structure. The simultaneous exfoliation and functionalization of graphene offers a promising advanced lubricant for industrial fabrication.

Automated summary

Electrochemical exfoliation of graphene is an environmentally friendly method for mass production. In this study, three ionic liquids (ILs) were used to exfoliate and functionalize graphene as a lubricant additive. The concentration of IL was found to affect the functionalization density of graphene, with higher concentrations resulting in higher densities. The tribological properties of the exfoliated graphene were influenced by the different anions present, with one particular IL showing the best performance, reducing the friction coefficient and wear volume by 32% and 39% respectively. The lubrication mechanism and structural evolution of the functionalized graphene were also examined, highlighting the formation of a tribo-film and disorder transformation as contributing factors. The simultaneous exfoliation and functionalization of graphene present a promising lubricant for industrial fabrication.