The relationship between surface microstructure and super-lubrication performance based on 2D LDHs

The mechanism of frictional energy dissipation suggests that layered double hydroxides (LDHs) could be ideal materials for achieving solid state superlubricity due to their strong adsorption effect and weak internal interactions. In this work, three metal ion-coordinated LDHs nanosheets were designed to investigate the specific effect of surface microstructure on frictional properties. The experimental results showed that the lubrication performance is determined by the surface structure, and the friction coefficient doubles (2 × 10−3 to 3.9 × 10−3) and the adhesion force increases by 62.3% (6.9–11.2 nN) when the divalent metal ions change from tetrahedral to octahedral coordination. Through crystal field stability energy analysis and density functional theory (DFT) calculations, the superlubricity of LDHs materials is attributed to two aspects: firstly, the existence of strong charge density transfer between LDHs nanosheets and the probe, known as the anchoring effect; secondly, the formation of an ultra-low sliding energy barrier interface between LDHs nanosheets and highly oriented pyrolytic graphite (HOPG). Therefore, the relationship between tribological properties and surface structure can guide future research on superlubricity materials.