Synergistic Tribological Enhancement in Water-Based Lubricants with Sodium Dodecylbenzenesulfonate-Modified Reduced Graphene Oxide

The extent of reduction in reduced graphene oxide (RGO) significantly affects its performance as a water-based lubricant additive. In this study, sodium dodecylbenzenesulfonate (SDBS)-modified RGO nanofluids with controlled degrees of reduction through a simple, low-temperature, water-bath reduction process are synthesized. This is achieved by varying the mass ratio of L-ascorbic acid (LAA) to graphene oxide (GO). The RGO-SDBS(V) sample, prepared at a 5:1 LAA-to-GO mass ratio, demonstrates an optimized lamellar structure and colloidal stability, with no sedimentation observed over 21 days. Tribological tests using a ball-on-disc tribometer demonstrate that incorporating 0.1 wt% RGO-SDBS(V) into pure water reduces the friction coefficient and wear rate by 78.8% and 88.9%, respectively. Surface analysis confirms the effective deposition of RGO-SDBS(V) and the formation of protective Fe₂O₃/SiO₂ tribofilms. The superior lubrication performance is attributed to the synergy between the intrinsic lubricity of RGO-SDBS(V) and friction-induced chemical reactions, as evidenced by X-ray photoelectron spectroscopy and Raman spectroscopy. These findings underscore the potential of SDBS-functionalized RGO in high-performance, water-based lubrication systems.