Adhesion energy of phosphorene on different pristine and oxidized metallic substrates

Black phosphorus and phosphorene have emerged as two-dimensional materials with remarkable tribological properties. However, recent experimental investigations revealed that their lubricating capabilities depend on substrates. This computational study employs density functional theory to quantify the adhesion energy of pristine and oxidized phosphorene monolayers on metallic substrates (aluminum, copper, iron and chromium) and their oxides ( Al 2 O 3 , Cu 2 O , Fe 2 O 3 and Cr 2 O 3 ), correlating this interfacial property with tribological performance. Results show that oxidized phosphorene presents higher adhesion on pure metals (Al, Fe, Cr) than pristine phosphorene, except for Cu, attributed to favorable interactions between oxygen non-bonding states and substrate empty states. Adhesion is more favorable on pristine metals than on oxides, with chromium and iron showing strong interactions due to partially filled 3d orbitals. This agrees with the friction coefficient decrease observed after scratching the iron substrate and removing the oxide layer. Conversely, negligible lubricating effects on other systems align with the low adhesion calculated for oxidized phosphorene on oxides and pristine copper. Charge redistribution analysis reveals an inverse relationship with adhesion strength on pure metals. Electronic structure analyses reveal system-dependent interfacial bonding characteristics, with some configurations inducing metallic character in phosphorene. These findings highlight the key role of layer-substrate adhesion in lubrication.