Durable and Scalable Superhydrophobic Colored Composite Coating for Subambient Daytime Radiative Cooling

Abstract

Passive daytime radiative cooling without any energy input has attracted significant attention due to its ability to spontaneously radiate heat into cold outer spaces. However, the distinctive structure and optical properties made radiative cooling materials white in appearance, which limits their use in actual application. In this study, poly(dimethylsiloxane) (PDMS), poly(ethyl cyanoacrylate) (PECA), polystyrene (PS), and pigments that selectively absorb visible light with high emissivity were adopted to fabricate a colored superhydrophobic radiative cooling coating through spraying and nonsolvent-induced phase separation. The as-fabricated yellow, red, and green PS/PDMS/PECA composite coatings exhibited high solar reflectivities of 92.8, 89.8, and 86.6% with strong infrared emissivities of 95.4, 95.3, and 96.3%, respectively, which correspondingly realized a subambient temperature reduction of 5.3, 3.5, and 2.5 °C. The self-cleaning property of the coating caused by superhydrophobicity helps protect the coating from contamination, favoring a stable outdoor cooling performance. Additionally, the composite coating was resistant to different chemical immersions, ultraviolet (UV) irradiation, sand impact, water impact, and sandpaper abrasion, which might improve the applicability of the material and promote the cooling materials toward large-area production for practical application.