Preferential Gas Adsorption at the Graphene-Water interface

TL;DR

This study reveals that graphene influences local water surface chemistry by preferentially adsorbing gas, forming nanostructures that depend on water degassing levels and surface hydrophobicity, impacting water-related phenomena.

Contribution

It demonstrates that graphene's interaction with water involves gas adsorption leading to nanostructure formation, highlighting the role of surface chemistry and hydrophobicity.

Findings

Gas adsorption on graphene causes nanostructure formation.

Degassed water prevents nanostructure formation.

Surface hydrophobicity influences gas adsorption behavior.

Abstract

The contact of water with graphene is of fundamental importance and of great interest for numerous promising applications, but how graphene interacts with water remains unclear. Here we used atomic force microscopy to investigate hydrophilic mica substrates with some regions covered by mechanically exfoliated graphene layers in water. In water containing air gas close to the saturation concentration (within ~40%), cap-shaped nanostructures and ordered stripe domains were observed on graphene-covered regions, but not on pure mica regions. These structures did not appear on graphene when samples were immersed in highly degassed water, indicating that their formation was caused by adsorption of gas dissolved in water. Thus, atomically thin graphene, even at a narrow width of 20 nm, changes the local surface chemistry of a highly hydrophilic substrate. Further, surface hydrophobicity significantly affects gas adsorption, which has broad implications for diverse phenomena in water.