Fabrication of superhydrophobic metallic porous surfaces via CO₂ and water processing

Superhydrophobic surfaces are of paramount importance for a great number of applications ranging from heat transfer to medicine. However, their mass production is challenging from environmental and scaling points of views. This work proposes a simple, scalable, production method for superhydrophobic surfaces and porous materials. In particular, highly hydrophobic CH₂/CH₃-grafted copper is achieved via exposure to a high-pressure supercritical CO₂ + H₂O environment. The hydrophobicity was further reinforced by using hierarchical macro-nanoporous copper prepared by a simple templating-annealing method reaching a water contact angle of ∼ 150°. The grafting is found to be durable in terms of ageing, abrasion and water impact. The superhydrophobic porous material is successfully used to separate oil emulsions from water. Molecular dynamics simulations are employed to investigate the underlying superhydrophobicity mechanisms further. We hypothesise that the obtained grafting results from a CO₂ hydrogenation reaction. The proposed approach may pave the way for the mass use of superhydrophobic surfaces and porous materials for anti-corrosion, anti-icing, separation, batteries, sensors, electronic materials, etc.