Universal passive radiative cooling behavior of aerogels

Aerogels have recently received extensive attention owing to their excellent thermal insulation performance. Thus, they are widely used for thermal management in buildings, aerospace, pipelines, and transportation for energy saving and emission reduction. However, silica aerogels have been confirmed to possess passive radiative cooling (PRC) capacities, which may seriously retard their thermal insulation performance. Therefore, whether PRC behavior is a universal property of aerogels is an urgent problem that can determine the eventual thermal management property of aerogels. Thus, in this study, six types of aerogels with different chemical components and microstructures, including silica aerogel, boron nitride aerogel, reduced-graphene oxide aerogel, Kevlar aerogel, poly(p-phenylene-2,6-benzobisoxazole) aerogel, and polyimide aerogels, are synthesized, and their PRC and thermal management behaviors are investigated. Impressively, all the above-mentioned aerogels showed extensive PRC performance, with a sub-ambient cooling ranging from 6.6 to 11.1 °C at night, regardless of their chemical component or color, confirming the universal PRC behavior of various aerogels. The PRC also significantly affects the thermal insulation properties of the aerogels. The reasons for the PRC of aerogels have been discussed. The findings of this study can help to a comprehensive understanding of the thermal management behavior of aerogels and guide to a better way to use aerogels in the actual environment by considering their PRC.