Superdurable, Flexible Ceramic Nanofibers for Sustainable Passive Radiative Cooling

High Resolution Image Download MS PowerPoint Slide Passive daytime radiative cooling can mitigate global warming but requires durable and resilient materials for real-world applications. Here, a robust superhydrophobic ZrO 2 –Al 2 O 3 nanofiber (sh-ZANF) membrane is fabricated via electrospinning followed by fluorine-free surface modification. Optically engineered sh-ZANF attains an extremely high solar reflectivity of 97.7% due to strong scattering at numerous fiber/air interfaces with a high refractive index contrast ( n fiber = 2.04, n air = 1). sh-ZANF also possesses a high atmospheric transparency window emissivity of 95.6% originating from phonon-polariton resonances of abundant Al–O/Zr–O bonds without a strong Reststrahlen effect. The optimal sh-ZANF membrane demonstrates subambient cooling of 6.6 °C and a maximum cooling power of 125 W/m 2 under 817 W/m 2 solar irradiance. Coverage by sh-ZANF cools building models, automobile models, and hand-held cameras under sunlight by 14.7 °C, 16.8 °C, and 11.1 °C, respectively. Equipping buildings with sh-ZANF is estimated to save more than 10 MJ/m 2 annually and reduce CO 2 emission by up to 27%. Moreover, these all-ceramic nanofibers can withstand temperatures exceeding 1400 °C, safeguarding buildings and their occupants during fire emergencies. Our sh-ZANF also displays attractive self-cleaning properties and successfully passes accelerated environmental aging tests, suggesting its applicability for future energy-efficient and sustainable cooling strategies.