Sustainable graphene oxide derived from palm shell waste as a tribological additive for Poly-Alpha-Olefin lubricants

This study presents a sustainable waste-to-nanomaterial approach by valorizing palm shell biomass into graphene oxide (GO) and demonstrates its novel application as a high-performance additive in poly-alpha-olefin (PAO) lubricants. Unlike conventional petroleum- or graphite-derived graphene materials, the GO synthesized in this work originates from agricultural waste, offering both environmental and economic advantages. Comprehensive structural and chemical characterizations confirmed the suitability of the bio-derived GO for tribological applications. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) revealed a flake-like, layered morphology favorable for tribofilm formation, while X-ray diffraction (XRD) showed a characteristic peak at 2θ ≈ 11.4°, indicating a well-ordered multilayer GO structure. UV–vis spectroscopy exhibited absorption bands at 231 and 295 nm associated with π→π* electronic transition of aromatic C = C bonds and n→π* transition of C = O functional groups, and FTIR analysis confirmed abundant oxygen-containing functional groups that promote interfacial interactions with the lubricant matrix. High-frequency reciprocating rig (HFRR) tests demonstrated that incorporating bio-derived GO significantly enhances the tribological performance of PAO. An optimal loading of 3 wt% GO reduced the wear scar diameter by 67%, lowered the friction coefficient by 14%, and increased tribofilm coverage by 13% compared to neat PAO. These improvements are attributed to the formation of a stable, low-shear-strength protective tribofilm facilitated by the unique structure and surface chemistry of the bio-derived GO. Overall, this work establishes palm shell–derived graphene oxide as an innovative, sustainable nanolubricant additive with strong potential for advanced and environmentally responsible tribological systems.