Ambient Conditions Determine the Wettability of Graphene

The nature of the graphene-water interaction (hydrophobic or hydrophilic) remains a matter of active debate. Earlier experiments studying water-graphene interactions showed graphene to be hydrophobic, in agreement with expectations. More recent works, however, reported that surface-adsorbed hydrophobic contaminants mask graphene’s intrinsic hydrophilicity. In this theoretical work, we use density functional theory to study the effects of “real life” conditions that affect the wettability of graphene. Our calculations reveal that the intrinsic water-graphene interactions have several components, viz., the van der Waals interaction, polarization, and electrostatic interaction. We further show that the presence of ambient gases, defects, and substrates influence these individual components, resulting in the contradictory observations made in experiments.