Enhanced photochemical stability of hydrophobic TiO2 via covalently anchoring near-monolayer octadecyl brushes and its robust superhydrophobic photocatalytic coatings

Conventional TiO 2 -based superhydrophobic coatings suffer from ultraviolet (UV)-induced photodegradation. Here, we prepared a modified TiO 2 (ODS@TiO 2 ) using octadecyltrimethoxysilane (ODS) via non-hydrolytic grafting. Fourier-transform infrared, X-ray photoelectron and 29 Si nuclear magnetic resonance spectroscopy confirm a near-monolayer octadecyl brush (4.6 ± 0.2 chains nm −2 ) anchored onto TiO 2 via robust Ti–O–Si bonds, whereas a hydrolytic product (ODS/TiO 2 -EW) contains a polysiloxane overlayer with sparse Ti–O–Si linkages. The Tauc plot shows that ODS@TiO 2 retains the bandgap of pristineTiO 2 . Nitrogen adsorption reveals an effective specific surface area of 42 m 2 ·g −1 for ODS@TiO 2 (vs 9 m 2 ·g −1 for ODS/TiO 2 -EW) and sufficient mesopores for mass transfer. Following UV exposure, the component of ODS@TiO 2 keeps constant, attributed to the synergy of Ti–O–Si bonds and octadecyl brushes that promote charge separation and provide steric shielding. A superhydrophobic coating was fabricated by mixing ODS@TiO 2 with ODS@SiO 2 prepared via analogous non-hydrolytic grafting. Scanning electron microscopy and 3D profilometry disclose a hierarchical structure featuring with 39% porosity and an average roughness of 5.8 μm. The coating exhibits superhydrophobicity, excellent photochemical stability, mechanical durability, and antibacterial properties, while the hydrolytic counterpart fails within 100 min of UV exposure. This work provides a scalable, fluorine-free strategy for fabricating UV-stable superhydrophobic coatings.