Molecular dynamics and experimental study of H₂-adsorption for enhanced tribological performance in ester-based lubricants

Hydrogen involvement in the tribochemical interaction between lubricants and metal surfaces can influence frictional performance. However, the lubrication mechanism remains unclear. This study investigates the effect of varying H₂ content in ester-based lubricants on frictional performance utilizing molecular dynamics (MD) simulation and experiments. An MD model for gas–liquid two-phase lubrication is established to simulate the influence of different H₂ content in the lubricant for the relative shear velocity between the two solid walls of 5 Å/ps at 3 GPa. Concurrently, optical microscopy and scanning electron microscopy (SEM) are employed to analyze the tribological behavior of ester-based oils containing different hydrogen concentrations during sliding. The results show that lubricants with higher H₂ content reduce the friction coefficient and mitigate wear more effectively. This pronounced effect is attributed to the adsorption and enrichment of H₂ molecules at interstitial sites within the iron lattice of the friction pair under high pressure and shear, which inhibits direct penetration of oil molecules into the surface. As a result, the lubricant film coverage is enhanced, and wear is reduced. This work elucidates the mechanism of the H₂ fraction in lubricants affecting frictional behavior, and provides theoretical guidance for developing engine oils for hydrogen internal combustion engines.