Scalable, flame-resistant, superhydrophobic ceramic metafibers for sustainable all-day radiative cooling

Passive daytime radiative cooling (PDRC), as a strategy to dissipate heat through an atmospheric trans-parency window (ATW) to outer space without any extra energy consumption, has been recently considered as a novel approach for global net-zero emissions. However, limited to expensive manufacturing, poor thermal/chemical stability, or insufficient weather-resistance, the development of a PDRC building material for long-term outdoor usages still remains a challenge. Here, a scalable superhydrophobic silica metafibers (sh-SMF) was fabricated via an electrospinning process combined with the fluorosilane-modification on fiber surface. The optically engineered sh-SMF could attain an extremely high average reflectivity (similar to 97 %) with near-zero absorption in the solar spectral region, due to the multiple backscattering at the fiber/air interfaces. In addition, the sh-SMF possessed a high average emissivity (similar to 90 %) in ATW, originated from the strong phonon resonances of the abundant Si-O bonds. Thus, the optimal sh-SMF realized a sub-ambient cooling performance of 6 degrees C (4 degrees C in nighttime) and the maximum cooling power of 112 W/m(2) (87 W/m(2) in nighttime) under a solar irradiance of-790 W/m(2). Besides, the temperature decline for the sh-SMF-covered building and vehicle models could also achieve 12.7 degrees C and 17 degrees C under sunlight, respectively. Noteworthily, the ceramic sh-SMF could withstand high temperatures over 1200 degrees C, which might effectively prolong the time for resident to evacuate from buildings in fireground situation. Moreover, the superhydrophobic surface (contact angle=155 degrees) of sh-SMF demonstrated attractive self-cleaning and anti-mildew properties. Furthermore, the excellent weather resistance against acid rain and ultraviolet exposure endowed the sh-SMF with long-term cooling performance. Finally, the sh-SMF with above mentioned properties opens a path for future energy-efficient and sustainable architectural applications. (c) 2022 Elsevier Ltd. All rights reserved.