Ultra-durable photothermal anti-/de-icing superhydrophobic coating with water droplets freezing from the outside in

In low-temperature, high-humidity environments, the condensation of water vapor within microstructures can initiate a detrimental cycle of hydrophobic failure, high-adhesion ice formation, and microstructural degradation, thereby limiting the practical application of superhydrophobic coatings in anti-icing and de-icing technologies. Therefore, enhancing the hydrophobic stability and mechanical durability of these coatings under such conditions is imperative. This study presents a novel approach where rigid Fe3O4 nanoparticles are encapsulated within porous diatomaceous earth (DME) and combined with high-adhesion acrylic resin (AR), resulting in a superhydrophobic photothermal coating that possesses both active and passive de-icing capabilities, fabricated through a straightforward one-step spraying technique. Nanosized Fe3O4 particles, modified for hydrophobicity and smaller than the critical nucleation radius, are densely packed within the DME micropores, forming a micronano structured coating with a contact angle of 160.1 degrees and a rolling angle of 2.1 degrees. This dense nanoparticle distribution facilitates preferential nucleation of ice crystal nuclei at the gas-liquid interface, rapidly leading to the formation of a robust and uniform ice shell, which effectively reduces the ice-solid contact area, resulting in loose ice droplets that initiate melting within 18 s. Additionally, the self-removal of condensed droplets from the surface enhances the water repellency and ice-phobic performance in low-temperature and high-humidity environments. The protection afforded by the DME microstructure and the releasable action of Fe3O4 nanoparticles allows the coating to maintain its superhydrophobic characteristics even after exposure to sandpaper abrasion, repeated de-icing, sand impact, and immersion in acid-base solutions. Thus, this robust and durable superhydrophobic photothermal coating, integrating active and passive de-icing functionalities, demonstrates substantial potential for application across various engineering domains.