Electrically induced superlubricity of electrophoretically deposited graphene-nanoplatelet coatings under aqueous glycerol-lubricated sliding conditions

Superlubricity has attracted increasing global interest as an effective strategy for reducing friction-related energy losses in response to rising energy demands. This study demonstrates the feasibility of achieving rapid superlubricity on a steel surface coated with graphene nanoplatelets by controlled electrical stimulation under aqueous glycerol lubrication. The results show that a current of +0.1 A promotes the exfoliation and alignment of the graphene nanoplatelets parallel to the sliding direction. This alignment promotes low-shear interlayer sliding, while detached graphene fragments effectively fill the surface asperities and microcracks, enabling continuous mechanical self-healing. As a result, a stable early superlubricity regime was established within 145 s, yielding a coefficient of friction (CoF) of ~0.007, and negligible wear. In contrast, a higher current of 3 A triggers excessive electrochemical oxidation and localised thermal effects that overwhelm the defect-healing capability of graphene, leading to insufficient surface passivation, severe wear, accompanied by 9.28-fold increase in CoF (~0.065). This study introduces a novel lubrication strategy for achieving superlubricity under electrified contact conditions and provides fundamental insights into the practical implementation of graphene-based superlubric systems in electrically driven sliding applications.