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 micro-nano structured coating with a contact angle of 160.1° and a rolling angle of 2.1°. 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.