Colorful Superhydrophobic Composite Coating for Efficient Passive Radiation Cooling

Radiation cooling is an ideal solution to the problems of environmental load and energy loss. Passive cooling is achieved by radiating heat into external space through light scattering, total internal reflection, and other methods. In addition, radiant cooling layers are commonly used in the construction industry, where they are exposed to the atmosphere and their vulnerability to sand, dust, and reduced radiant cooling capacity. Therefore, radiant cooling layers incorporating superhydrophobic properties have emerged. In this work, we report a polyacrylate white coating based on silica and hollow glass beads as fillers, which is further modified with polydimethylsiloxane for superhydrophobicity. The coating has a strong solar reflectance (96%) and mid-infrared emissivity (97%), and the maximum temperature drop during outdoor real-time cooling is about 7 °C. In addition, two colored coatings were prepared for the aesthetics of architectural coatings, which also have good radiative cooling properties. More importantly, the excellent superhydrophobic property of the coating ensures the coating’s self-cleaning performance and avoids the influence of dust on the radiant cooling layer. The excellent durability of the prepared coatings was demonstrated by various stability tests. Our work has great application prospects for energy loss and sustainable outdoor service.