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

Abstract

• Porous PVDF composite sheet (PPCS) was fabricate by scalable melt-processing using cheap micron-scale table salts as pore templates and nano-alumina as fillers. • PPCS exhibits high solar reflectivity of 91.8% and high infrared emittance of 94.3%, enabling sub-ambient daytime/nighttime radiative cooling of 8.3 °C/12.0 ℃. • PPCS has satisfied strength, hydrophobic self-cleaning, and flame retardance for practical application. • This work provides a low-cost, organic-solvent-free strategy to fabricate thick PDRC materials. 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 °C with a cooling power of 61.7 W·m -2 and nighttime cooling of 12.0 ℃ 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.