Improving the long-term weatherability of commercial radiative cooling materials by applying a fluorine-free superhydrophobic coating

Abstract

Daytime radiative cooling (RC), a technology that dissipates heat to the cold universe in a remote, passive manner, has great potential to decarbonize the energy sector for buildings. However, there remains a big gap between the high-performance RC materials developed in laboratory and their real-world application in buildings. Here we propose an approach to improving the long-term durability of commercial RC materials against severe weather conditions by applying a fluorine-free superhydrophobic coating. We realized surface superhydrophobicity through a simple spray coating method with a mixture of silica particles, both micro- and nano-sized, and polydimethylsiloxane, while keeping the radiative properties of the RC materials nearly unchanged (only ∼1% degradation). The modified RC materials were subjected to a variety of intensive weathering and outdoor tests, and demonstrated remarkably improved durability compared to the commercial one, with the degradation of radiative properties being <6%. Based on such weatherability improvement, EnergyPlus simulations suggested that the modified RC materials can lead to an additional annual carbon reduction of ∼1 × 10⁷ tons of CO₂ in mainland China after dust accumulation for three years. This effective, environmentally-friendly, and easy-to-scale coating strategy enables long-term anti-weather performance of commercial RC materials for energy-efficient buildings.