Polyurethane-SiO2 tandem composite fibrous membrane for passive daytime radiative cooling

Passive daytime radiative cooling (PDRC) is a promising energy-saving approach for intelligent textiles. However, the preparation process for most PDRC materials is complex and costly, and their surfaces are susceptible to contamination, leading to poor durability and thereby limiting their application fields. Herein, we report on a tandem passive radiation-cooled fibrous membrane consisting of elastic polymer and nanoparticles (NPs), which can achieve dual-functions of self-cleaning and passive radiative cooling. Specifically, a large number of SiO₂ NPs on the surface of the composite fibrous membrane exhibit phonon-enhanced Fröhlich resonance, facilitating the emission of infrared radiation and imparting excellent radiation cooling performance to the fibrous membrane. This is reflected in the membrane's maximum effective reflectivity in the solar spectrum (88.29 %) and its infrared emissivity within the atmospheric window (94.9 %). On the other hand, the hydrophobic SiO₂ particles, with their low surface energy, enhance the roughness of the fibrous membrane surface, resulting in a water contact angle of 145° for the fibrous membrane. Consequently, this tandem passively cooled fibrous membrane boasts a self-cleaning surface, which overcomes the fundamental challenges of radiative cooling and demonstrates sustainability under harsh conditions, further broadening its practical application areas.