Salt-template-assisted melt-processed porous poly (vinylidene fluoride) nanocomposites for highly efficient all-day passive radiative cooling

Passive daytime radiative cooling (PDRC) has recently attracted tremendous attention as one promising thermal management strategy. However, a large amount of hazardous organic solvent is usually used for fabricating most PDRC materials, increasing the manufacturing cost and posing serious environmental problems. Here, a scalable melt-processed approach was adopted to fabricate porous poly (vinylidene fluoride) composite sheet (PPCS) using cheap micron-scale table salts as pore templates and nano-alumina as fillers. The obtained PPCS exhibits a high solar reflectivity (91.8 %) and high infrared emittance (94.3 %), enables an efficient sub-ambient daytime radiative cooling of 8.3 degrees C with a cooling power of 61.7 W.m(-2 )and nighttime cooling of 12.0 degrees C with a cooling power of 148.3 W.m(-2). In addition, PPCS has satisfied strength, hydrophobic self-cleaning, and flame retardance for practical application. This work provides a scalable, low-cost, organic-solvent-free approach to fabricate PDRC materials with varying thickness from micron scale to centimeter scale.