Highly spectrally selective dual-layer cellulose-based composite material for daytime radiative cooling

Passive radiative cooling is a key technology to solve the global warming and energy waste caused by refrigeration. However, because of the high price and complex manufacturing process, the application of daytime radiative cooling materials in the field of building materials is hindered. Here, we studied a low-cost radiative cooling cellulose-based composite material prepared from wood powder that exhibits highly selective infrared emission and high solar reflectivity. And we use the evaporation deposition technique to form a dual-layer structure with silica microspheres in the lower layer. The radiative cooling film based on the intrinsic absorption of lignocellulose and silica microspheres exhibits not only high infrared emissivity of 98.7% in the 'atmospheric window' range but also exhibits high reflectivity of 98.44% in the visible light range. We have also found that the performance of the radiative cooling film is the best when the content of silica microspheres reaches 30 wt%, and the film exhibits a cooling of 9.6 degrees C under direct sunlight. The preparation method of low-cost and high-performance radiative cooling material provided in this article is expected to provide a reference for the application of radiative cooling materials in building materials.