Dispersion stability and friction-reduction mechanism of carboxyl/hydroxyl-modified graphene oxide in oil-lubricated systems

Purpose To address nanoparticle agglomeration and deactivation in lubricant additives, this study enhanced graphene oxide (GO) dispersion stability and tribological properties in pentaerythritol oleate (PETO) base oil through carboxyl/hydroxyl functionalization. Design/methodology/approach By combining molecular dynamics simulations with tribological experiments, this paper investigated the dispersion mechanisms and operational adaptability of functionalized GO. Findings Results demonstrate that carboxyl groups (-COOH) and hydroxyl groups (-OH) on GO establish a bipolar electrostatic potential distribution. The highly negatively charged oxygen atoms in carboxyl groups attract positively charged hydrogen atoms on PETO alkyl chains, while the strongly positive hydrogen atoms in carboxyl groups form hydrogen bonds with ester oxygen atoms. Hydroxyl groups contribute to synergistic adsorption through moderate electrostatic potential. Collectively, these interactions suppress agglomeration and promote protective film self-assembly at the friction interface. The GO-enhanced lubricant exhibits excellent friction-reducing performance under complex operating conditions, achieving a 9–42% reduction in the coefficient of friction relative to the base oil. The functional groups deliver dual “dispersion-lubrication” functionality through electrostatic and hydrogen bonding interactions. Carboxyl groups dominate adsorption (binding energy enhancement: 88.7%), while hydroxyl groups strengthen interfacial bonding and structural curvature provides steric hindrance. Practical implications Combined molecular dynamics simulations and experimental studies jointly reveal that hydroxyl and carboxyl functional groups on the graphene oxide (GO) surface establish a “dispersion-lubrication dual-function mechanism” through electrostatic-hydrogen bonding synergy. The bipolar sites not only confer dispersion stability to GO – effectively suppressing agglomeration-induced deactivation – but also ensure persistent adsorption capability at friction interfaces, constructing stable tribofilms. Originality/value This triad synergistically overcomes agglomeration. The findings demonstrate that interfacially functionalized graphene oxide effectively resolves nanoparticle agglomeration in lubricant additives, establishing a theoretical foundation for high-performance lubricant design. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2025-0352/