Extreme-environment tolerant superhydrophobic montmorillonite/hollow SiO2 composite coating as building radiative cooler for scale energy conservation

Abstract

Passive radiative cooling (PRC), as a promising energy-saving strategy can obtain sub-ambient cooling by reflecting solar irradiation and dissipating excessive heat to outer space without any energy consumption. However, for outdoor environment, especially extreme environment, the cooling performance of PRC materials may be affected by dust pollution and acid-alkali corrosion. Herein, we proposed a superhydrophobic radiative cooling composite coating prepared by modified montmorillonite (MMT) and hollow SiO2 (H-SiO2) for all-day cooling with low-cost raw materials. Due to stronger backscattering of hollow structure, this coating can effectively reflect incident sunlight, accounting for the high solar reflectivity (0.93) and the mid-infrared emittance (0.94) originated from the combination of MMT and H-SiO2. Subsequently, it exhibits satisfied cooling performance with the temperature drop of 4.1 ℃ under an averaged solar irradiation of 1020 W/m2 in the daytime and 6.2 ℃ in the nighttime. Moreover, the superhydrophobic surface of the coating prevents the dust pollution and the corrosion of acidic and alkaline solutions, broadening its application in the extreme environment. Thereby, our work lights a path on the novel energy-saving coating for extreme environment.