Whisker-based coatings with high passive radiative cooling efficiencies even in harsh environments

This study presents a one-step fabrication method for developing sprayable waterborne coatings that synergistically exhibit high solar reflectance (94.7%) and infrared emittance (0.96), along with robust superhydrophobicity for passive radiative cooling (PRC). Unlike conventional multi-step methods, our superhydrophobic (SH) PRC coating achieves a superior balance of optical performance and superhydrophobicity through spontaneous interactions between Al₂O₃ whiskers, PTFE, and silicone during coating formation. These interactions lead to the spontaneous formation of a unique hierarchical structure with an optimal pore size distribution, which not only maximizes Mie scattering to achieve broadband solar reflection but also imparts intrinsic superhydrophobicity. Results indicate a temperature reduction of 22 °C compared to commercial coatings under solar radiation in harsh environments. Furthermore, the coating maintains its performance after mechanical abrasion and UV aging, addressing critical durability challenges.