Silica-bridged inorganic-organic hybrid membrane for efficient daytime radiative cooling

Passive daytime radiative cooling (PDRC) has been considered as a cost-effective technology for efficient energy consumption and utilization, in which the heat is directly delivered into the outer space (3 K) through reflection and radiation. To achieve the high-performance PDRC, textile-based porous membranes are widely employed as radiators, however, the PDRC efficiency affected by the mechanical robustness. Herein, inspired by natural spider silks, a micro-/nano-sized hierarchical membrane-based radiator, which is rationally constructed with the interconnected polyethylene oxide (PEO) nanofibers bridged by the robust silica (SiO2) microspheres, was fabricated with the assistance of electrospinning. This as-prepared membrane features a hierarchically porous structure and a strong interfacial binding, resulting in the optimal optical and mechanical properties. For example, in the presence of a silane coupling agent, the tensile strength and the toughness of the resultant organic-inorganic hybrid membrane are enhanced by 7.1 and 7.2 times, respectively, compared to the organic PEO-based membrane. Furthermore, the assembled radiator demonstrates a temperature difference between 16.1 and 27.4 degrees C, accompanied by an average solar reflectance of 95.6 % and an average atmospheric window emittance of 89.9 %. This work provides a promising solution for achieving daytime radiative cooling at a reasonable cost and this technology could be extended into a wide range of application fields, such as smart buildings and aerospace industries.