Robust structure and superhydrophobic PLA/ZrO2 fiber aerogel for daytime radiative cooling

Daytime radiative cooling as an environmentally energy-saving strategy, achieves cooling without any power consumption by reflecting sunlight and radiating energy to outer space. In our work, an eco-friendly and degradable poly(lactic acid) (PLA) fibers derived from discarded nonwovens are used to prepare aerogels by combing with ZrO 2 nanoparticles with silane coupling agent (VTMS) crosslinking. The composite aerogel with low density (26.3-30.7 mg/cm 3 ) exhibits high solar reflectance (77%), emissivity (94.31%), low thermal conductivity, and high compressive stress (9.0 kPa under 60% compressive strain). Thermal insulation test demonstrates that the aerogel can achieve temperature drops of 31.3 °C and 41.4 °C under the temperature of heating table 60 °C and 80 °C. Radiative cooling test shows aerogel with 15 wt% ZrO 2 can achieve a temperature drop of 9.14 °C during daytime. Meanwhile, the aerogel cooler presents excellent superhydrophobic (150°), self-cleaning performance, and cyclic compression performance. This findings will promote the field of passive radiative cooling toward a greener and more sustainable direction.