Photocatalytic Superamphiphobic Coatings and the Effect of Surface Microstructures on Superamphiphobicity

In recent years, superamphiphobic coatings have been widely used in industrial transportation and environmental treatments because of their unique liquid repellency. In this study, WO3-TiO2 nanorods/SiO2 were used as the constructor of surface microstructures, and 1H,1H,2H,2H-perfluorodecyltriethoxysilane was used as the provider of low surface energy, and a photocatalytic superamphiphobic coating (FTS coating) was prepared. The microstructure and chemical composition of the coating was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The coating exhibited excellent photocatalytic activity toward degradation methyl red and nitric oxide (NO), and the degradation efficiency to NO reached 47.8%. Also, the advanced contact angle and the hysteresis angle of water, glycol, glycerol, and olive oil was used to evaluate the superamphiphobicity. After 7 days of ultraviolet (UV) aging, five cycles of airbrush flushing and 48 h of immersion in acid, salt, and alkali solutions, the FTS coating still exhibits excellent amphiphobicity, which lays a foundation for its large-scale applications in the concrete exterior wall. The surface microstructure and the formation of air pockets are a prerequisite for superamphiphobicity, which promotes the liquid on the coating surface into the Cassie-Baxter state. Furthermore, the formation of air pockets is closely related to the gas adsorption capacity and the specific surface area (SBET) of the surface microstructure on the coating surface. The coatings with different SBET constructed and the advanced contact angle were measured. The influence of air pockets on the superamphiphobicity of coatings was studied in combination with the optical microscope. The understanding that SBET further influences superamphiphobicity by affecting the surface air pockets is proposed.