Durable Superhydrophobic Surfaces with Self-Generated Wenzel Sites for Efficient Fog Collection

Harvesting freshwater from fog is one of the possible solutions to the global water scarcity crisis. Surfaces with both hydrophobic and hydrophilic regions are extensively employed for this purpose. Nevertheless, the longevity of these surfaces is still constrained by their delicate surface structures. The hydrophilic zones may become damaged or contaminated after repeated use, thereby compromising their effectiveness in fog collection. The preparation of generally applicable durable superhydrophobic coatings with self-generated Wenzel sites is reported here for long-term efficient and stable fog collection. The coatings are prepared by depositing the poly(tannic acid) coating as the primer layer on various substrates, self-assembly of trichlorovinylsilane into staggered silicone nanofilaments, and then thiol-ene click reaction with 1H,1H,2H,2H-perfluorodecanethiol. The coatings demonstrate remarkable static superhydrophobicity, robust impalement resistance, and stable self-generated Wenzel sites for water droplets. Therefore, the fog collection rate (FCR) of the coatings reaches 2.13 g cm-2 h-1 during 192 h continuous fog collection, which is triple that of bare substrate and outperforms most previous studies. Moreover, the systematic experiments and models have revealed that the key factors for achieving high FCR on superhydrophobic coatings are forming condensed droplets approximate to 1 mm in critical radius and a Wenzel site proportion of 0.3-0.4. Durable superhydrophobic coatings applicable onto various substrates are prepared by a three-step methodology. The coatings exhibit excellent static superhydrophobicity and impalement resistance. The coatings possess self-generated Wenzel sites during fog collection, enabling a consistent high fog collection rate over an extended period of continuous operation. The key to achieving a higher fog collection is the suitable Wenzel sites proportion. image