A green approach to high-efficiency passive radiative cooling coatings with repairable self-cleaning property

Passive daytime radiative cooling offers an efficient solution to the global energy crisis by reflecting sunlight and radiating heat into space. However, its practical application remains constrained by challenges such as dust pollution, daily wear and tear, corrosion, and the release of toxic gases, etc. In this study, we developed a multi-component superhydrophobic radiative cooling coating, which is composed of highly reflective BaSO₄ nanoparticles, infrared emissive polydimethylsiloxane (PDMS) polymer, hydrophobic silica, and water-based binder. A novel strategy was employed to prevent the release of organic pollutants during the fabrication process by pre-polymerizing the PDMS polymer into microspheres. The coating demonstrates excellent solar reflectivity (97.1 %) and mid-infrared emissivity (95.4 %), achieving a cooling effect of 10.4 °C below ambient temperature during the day and 4.3 °C at night. Additionally, it exhibits outstanding and repairable superhydrophobic property, with a water contact angle of 171.4° and a rolling angle of 1.3°. When the superhydrophobicity of the coating surface is degraded, it can be repaired through abrasion treatment with sandpaper. Moreover, the eco-friendly coating can be applied to various substrates via simple methods such as rolling, brushing, or spraying, and can be incorporated with water-based pigments to fulfill aesthetic requirements. Its excellent radiative cooling, self-cleaning, and weather resistance make it suitable for outdoor cooling systems such as buildings and vehicles.