Biodegradable radiative cooling membrane based on electrospun silk fibroin fiber

Abstract Biodegradable radiative cooling materials can achieve both zero‐energy cooling and environmental friendliness. Natural silk cocoon exhibits both high solar reflectivity and mid‐infrared emissivity owing to its unique structure and composition, while it possesses excellent biodegradability. Herein, we restructure the natural silk by electrospinning to obtain scalable and biodegradable silk fibroin (SF) fiber membranes with enhanced optical properties. Specially, nano‐sized fibers exhibit better optical properties than micrometer‐sized ones. The fabricated SF nanofiber membrane can achieve ultra‐high average solar reflectance and infrared emittance of 96% and ~97%, respectively. Such outstanding optical properties enables the fiber membrane to yield an average sub‐ambient cooling temperature of ~6°C in the outdoor environment even under a peak solar intensity of ~800 W m −2 . Overall, the resulted SF fiber membranes promise a wide range of applications such as building energy efficiency, cold‐chain transportation, in‐vehicle temperature control, outdoor precision instrument protection and outdoor personal thermal management.