“Pore in Pore” Engineering in Poly(dimethylsiloxane)/Silicon Oxide Foams for Passive Daytime Radiative Cooling
Jing‐hui Yang, Qingwen Pu, Wenjin Hu, Qingqing Liu, Xin Li, Wenhao Huang, Nan Zhang, Yong Wang
Abstract
Passive daytime radiative cooling (PDRC), an energy-saving and environmentally friendly strategy, achieves cooling without any power consumption by reflecting sunlight and radiating energy to outer space. Herein, it is shown that a porous-structured poly(dimethylsiloxane)/silicon oxide (PDMS/SiO 2 ) composite foam is fabricated through “pore in pore” engineering, in which a three-dimensional self-supporting silicon dioxide (SiO 2 ) network is constructed in the pores of PDMS foam fabricated via freezing casting. The PDMS/SiO 2 foams exhibit a hierarchical porous structure like “SiO 2 assembling pores in PDMS micropores” and significantly benefit the reflectivity and infrared emissivity. An average solar reflectivity of ∼90.1% within a full spectral range of 0.3–2.5 μm and an average emissivity of ∼94.1% in the atmospheric window allow for the temperature inside the foam cavity to drop by ∼11.1 °C under direct sunlight with the solar radiation intensity of 871 W m –2 . Notably, the hierarchical porous PDMS/SiO 2 foams exhibit excellent thermal insulation, antifouling, and hydrophobic performances, weakening the heat flow from the external environment and ensuring long-term outdoor use. Such a powerful radiative cooling performance integrated with thermal insulating and antifouling capability by the foams constructed by “pore in pore” engineering offers a way to efficiently manage sunlight radiation energy to make devices, vehicles, buildings, and other urban objects cooler and helps to save energy in an outdoor sunlight environment.