▎ 摘　　要

The development of water-based lubricants with well dispersed ultrafine particles is in high demand. In this article, graphene oxide (GO) nanosheets/carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs-COOH) hybrids have been synthesized via vacuum filtration of a solution hybrid dispersion, as additives for water-based lubricants. The tribological performance of GO/MWCNTs-COOH hybrids in water was systematically investigated. The lubrication properties of water-based lubricant can be significantly improved by adding GO/MWCNTs-COOH hybrids in comparison with adding only GO nanosheets or MWCNTs-COOH as lubricant additives. Notably, the water with as little as 0.7 wt% of GO/MWCNTs-COOH hybrids exhibits the best lubrication performance in terms of friction and wear reduction. This unique tribological performance of GO/MWCNTs-COOH hybrids in water suggests the existence of a synergistic effect of GO and MWCNTs-COOH on reducing friction and wear.