Facile Fabrication of Fluorine‐free Silica‐based Superhydrophobic Coating Using Acid‐catalyzed Silica Adhesive

Eco‐friendly, easy, fast and scalable strategies for robust superhydrophobic coatings are of great significance for industrial application. Herein, a robust fluorine‐free superhydrophobic coating is prepared via spraying the mixed suspension which consist of silica nanoparticles and hydrophobic acid‐catalyzed silica sol. The adhesive which is synthesized through hydrolyzation and condensation of silane precursors (TEOS, MTMS, HDTMS) shows good compatibility with silica nanoparticles. When the mass ratio of SiO2/adhesive was 0.025 : 1, the prepared coating exhibited good non‐wettability with a WCA of 164° and a RA of 2°. Moreover, due to the hydrophobic acid‐catalyzed silica sol which bonds silica nanoparticles together, the coatings also demonstrate well mechanical robustness. After 60 g sand impacted on the surface of as‐prepared coating from a height of 1 m, the surface still showed superhydrophobicity with a WCA of 152° and a RA of 6°. And the as‐prepared coating could endure the sandpaper abrasion for 80 cm. Furthermore, the adhesion of as‐prepared coatings to substrates can reach the highest 5 A level. The current work provides an easy and promising approach to meet the challenges in practical applications simultaneously posed by the fluorine‐free, low‐cost, mechanical robustness as well as large‐scale preparation of silica‐based superhydrophobic coatings. A hydrophobic acid‐catalyzed silica sol was firstly synthesized to bond the silica nanoparticles together to form a mixed suspension. The fluorine‐free silica‐based superhydrophobic coating was fabricated from this mixed suspension with spray‐coating method. The as‐prepared superhydrophobic coating coated steel demonstrated an excellent superhydrophobicity with a water contact angle of 164°.