Enhanced lubricity and anti-wear performance of zwitterionic polymer-modified N-enriched porous carbon nanosheets as water-based lubricant additive

The zwitterion polymer functionalized N-enriched porous carbon nanosheets were prepared via pyrolysis and etching of pyridine-coordinated polymer for N@PCNS. Subsequently, N@PCNS was modified with polydopamine to grow the zwitterionic polymer (PEIS), thereby acquiring PEIS functionalized N@PCNS (PEIS-PCNS). The exceptional tribological performance of PEIS-PCNS was attributed to the synergistic lubrication effects of N@PCNS along with the zwitterionic polymer PEIS, which facilitates the formation of a stable protective carbon film over the worn surface via complicated tribo-chemical reaction. Meanwhile, the presence of a hydration layer encapsulated by PEIS as the boundary lubricating film proves highly conducive for friction reduction. The average coefficient of friction showed a dramatic decrease to 0.17 from 0.63, and the wear depth of stainless steel dropped 64%.