Surface roughness induced superhydrophobicity of graphene foam for oil-water separation.

Surface free energy and roughness are two predominant factors governing the hydrophilicity/hydrophobicity of materials. This paper reported the surface roughness induced hydrophobicity of graphene foam by incorporating silica nanoparticles onto graphene sheet via a sol-gel method and subsequent modification using silane. Various techniques were employed to characterize the morphology, composition and surface properties of sample. The results showed that the as-prepared graphene foam exhibited a superhydrophobic surface with a high water contact angle of 156°, as well as superoleophilicity with excellent adsorption capacities for a variety of oil compounds. Benefiting from the integration of enhancement on the surface roughness and reduction on the surface free energy of material, the graphene foam developed in this study had the capability to effectively separate oil-water mixture with excellent stability and recyclability.