High‐Strength Flexible Membrane with Rational Pore Architecture as a Selective Radiator for High‐Efficiency Daytime Radiative Cooling

Abstract

Abstract Passive daytime radiative cooling, a cooling strategy with no energy consumption, has attracted significant attention as a supplement to traditional active energy cooling techniques. However, realizing a practicable radiator with excellent spectral selectivity and strength via facile, scalable, and economical manufacturing remains a challenge. In this study, a spray‐phase‐separation strategy that utilizes spray and high‐speed airflow to regulate the phase evolution kinetics during the evaporation‐induced phase separation process for rational pore architecture is proposed. The fabricated poly (vinylidene fluoride‐co‐hexafluoropropene) based flexible hierarchically porous complex membrane (FHPCM) shows an excellent spectral selectivity with an average reflectance of 97.2% and 52.9% in 0.24–2.5 and 2.5–8 µm wavelength range, respectively. In addition, FHPCM demonstrates an average emittance of 93.5% in the atmospheric window with an effective thickness of 313 µm, thus realizing a sub‐ambient radiative cooling of 14.9 °C and an inaccurate noontime radiative cooling power of 100 W m −2 under an average solar intensity of ≈1250 W m −2 . Outdoor applications further confirm the excellent capacity of FHPCM for cooling cars and buildings, with a maximum T cooling of 7.4 °C. In addition, the economical FHPCM possesses good strength (64.6 MPa), flexibility, hydrophobicity, and weatherability.