Superhydrophobic\nPorous Coating of Polymer Composite\nfor Scalable and Durable Daytime Radiative Cooling

Abstract

Passive\ndaytime radiative cooling (PDRC) technology provides\nan\neco-friendly cooling strategy by reflecting sunlight reaching the\nsurface and radiating heat underneath to the outer space through the\natmospheric transparency window. However, PDRC materials face challenges\nin cooling performance degradation caused by outdoor contamination\nand requirements of easy fabrication approaches for scale-up and high\n cooling efficiency. Herein, a polymer composite coating of polystyrene,\n polydimethylsiloxane and poly(ethyl cyanoacrylate) (PS/PDMS/PECA)\nwith superhydrophobicity and radiative cooling performance was fabricated\nand demonstrated to have sustained radiative cooling capability, utilizing\nthe superhydrophobic self-cleaning property to maintain the optical\nproperties of the coating surface. The prepared coating is hierarchically\nporous which exhibits an average solar reflectance of 96% with an\naverage emissivity of 95% and superhydrophobicity with a contact angle\nof 160°. The coating realized a subambient radiative cooling\nof 12.9 °C in sealed air and 7.5 °C in open air. The self-cleaning\nproperty of the PS/PDMS/PECA coating helped sustain the cooling capacity\nfor long-term outdoor applications. Moreover, the coating exhibited\nchemical resistance, UV resistance, and mechanical durability, which\nhas promising applications in wider fields.