Alumina Fiber Membrane Prepared by Electrospinning Technology for Passive Daytime Radiative Cooling

Abstract Passive daytime radiative cooling (PDRC) achieves cooling by simultaneously reflecting sunlight and radiating heat to outer space, without consuming any external energy. Traditional PDRC designs use organic materials that are prone to aging and secondary pollution under solar illumination. Here, a flexible alumina fiber membrane (FAFM) is prepared using electrospinning technology. The fiber‐membrane hierarchical structure ensures macroscopic flexibility, allowing this inorganic material to be assembled on complex surfaces just like organic materials. It can efficiently dissipate heat by emitting infrared radiation that matches the atmospheric window and scattering sunlight. Importantly, it is notable that no aging phenomenon occurs even under prolonged ultraviolet irradiation, which brings additional benefits to its green energy‐saving properties. As a result, its outstanding fire resistance and thermal insulation prevent the possibility of spontaneous combustion in extremely hot weather during the summer and may serve as a multifunctional insulation layer for buildings. This preparation method promotes surface design based on more inorganic structural materials in the future, enabling the design of more low‐cost, highly flexible inorganic PDRC materials.