Tuning Surface Wettability and Adhesivity of a Nitrogen-Doped Graphene Foam after Water Vapor Treatment for Efficient Oil Removal

An environment-friendly water vapor treatment for realizing a highly hydrophobic (contact angle ≈147.5) and oleophilic N-doped graphene foam (NGF) for efficiently removing oil from oil/water emulsions is presented. 3D porous networks of NGF with high N content are prepared by subjecting a mixture of graphene oxide and 5 vol% pyrrole to a hydrothermal process; the mixture is then freeze-dried and annealed under a N₂ atmosphere. The surface wettability and adhesivity are tuned through water vapor treatment by forming a low-surface-energy hydrocarbon layer, with no chemical modification. The effectiveness of the hydrophobic/oleophilic NGF in removing oil from an oil/water emulsion is demonstrated.