Water Chemistry beneath Graphene: Condensation of a Dense OH-HO Phase under Graphene.

Room temperature oxygen hydrogenation below graphene flakes supported by Ir(111) is investigated through a combination of X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations using an evolutionary search algorithm. We demonstrate how the graphene cover and its doping level can be used to trap and characterize dense mixed O-OH-HO phases that otherwise would not exist. Our study of these graphene-stabilized phases and their response to oxygen or hydrogen exposure reveals that additional oxygen can be dissolved into them at room temperature creating mixed O-OH-HO phases with an increased areal coverage underneath graphene. In contrast, additional hydrogen exposure converts the mixed O-OH-HO phases back to pure OH-HO with a reduced areal coverage underneath graphene.