Radiation-cooled aramid composite films featuring tunable TiO2 nanorod arrays anchored on the surface of 2D Mica nanosheet for passive daytime radiative cooling application

Radiation-cooled films accompanying the required high solar reflectance and emissivity as well as environmental durability are challenging to develop for passive daytime radiant cooling (PDRC) applications. Herein, an inorganic dielectric scatterer, producing strong scattering in the visible to near-infrared wavelength band, had been constructed by tunable TiO2 nanorod arrays with high refractive index on the surface of 2D Mica nanosheets with good mechanical strength and chemical stability. Subsequently, radiation-cooled aramid composite films featuring a well-organized 2D layered stack structure of inorganic scatterer was developed for PDRC applications. By the feature inorganic scatterers effectively stimulating multi-level scattering of light through TiO2 nanorod arrays and multi-layered Mica structures, the radiation-cooled aramid composite films have ultra-high reflectivity of 97.5% and emissivity of 96.3% in sunlight, and achieve subambient cooling of 8.62°C for daytime and 4.84°C for nighttime. Meanwhile, the well-organized lamellar PDRC films possess high strength (98 MPa) as well as excellent environmental durability, including scratch-resistant, UV radiation-resistant and flame retardance, suggesting its great potential in PDRC for thermal regulation.