On the origin of the surface superhydrophobicity of rough-textured inorganic materials with intrinsic hydrophilicity
Abstract
In mechanism, the surface superhydrophobicity is often thought to be the result of trapping-air within the grooves leading to a composite solid-liquid-air interface. However, the mechanism cannot reasonably reflect why the rough surfaces of intrinsically hydrophilic materials are capable of behaving hydrophilicity or superhydrophobicity. In this work, several typical rough-textured inorganic materials (i.e. metal oxide, sulfide, selenide and halide) endowed with intrinsic hydrophilicity are taken as example to reveal the superhydrophobic origin of intrinsically hydrophilic materials. Their wettability for the same rough-textured surface is usually hydrophilic when dried in N2, while is hydrophobicity or superhydrophobicity when in O2. The distinct difference in the wettability is closely related to the anion vacancies such as oxygen-, sulfide- and halogen-ion ones. From the generation of H2O2 in water-droplet on their rough-textured surfaces, it is found that the H2O2 yield increases with an increase of their hydrophobicity, and decreases with enhancing their hydrophilicity, indicating an evidence dependence of their surperhydrophobicity on the absorption of O22- on their surfaces. DFT calculation shows that the introducing Va can give a higher adsorption-energy for oxygen molecular species (especially O22-) than N2 and H2O. Hence, we propose that the presence of abundant Va on the intrinsically hydrophilic inorganic materials can result in the formation of preferential O22- adsorption layer in the grooves, which endows these inorganic materials with superhydrophobicity. Our results can provide a further insight into the origin of superhydrophobicity for intrinsically hydrophilic materials, and guide the design of water-proof functional surfaces
- This article is part of the themed collection: 2024 Inorganic Chemistry Frontiers HOT articles