Durable and mechanically robust superhydrophobic radiative cooling coating

Abstract

Passive radiative cooling (PRC) presents a promising strategy for reducing energy consumption by reflecting sunlight and radiating heat through atmospheric windows. Although extensive progresses have been achieved in efficient radiative cooling, it still faces several challenges that hinder its practical implementation, such as susceptibility to contamination, vulnerability to mechanical damage, and poor resistance to aging and corrosion. Herein, we report a robust superhydrophobic porous coating with nano-globules (SHPo-ME) for efficient all-day passive radiative cooling, which is thermal polymerized by Methyl methacrylate (MMA) and Ethylene dimethacrylate (EDMA). Due to the sufficient scattering by the nano-globule structures and the stretching vibration of the chemical bonds in the polymer, the SHPo-ME coating exhibits superior solar reflectance (97.6 %) and long-wave infrared emittance (98.3 %), realizing sub-ambient cooling of 8.4℃ under the solar intensity of 820 W⋅m−2 and 5.8℃ in the night. Moreover, the interconnected nano-globules increase the surface roughness, rendering the surface to exhibit remarkable superhydrophobicity with contact angle of up to 165° and sliding angle lowered to 2.4°. Importantly, the robust SHPo-ME coating possesses excellent self-cleaning ability, mechanical stability, recoverable superhydrophobicity, and anti-aging/anti-corrosion property. The as-prepared SHPo-ME coating can also be milled into powder and used as paint. This paint can be efficiently sprayed onto any arbitrary substrates on a large scale, demonstrating great potential for long-term outdoor application such as buildings, vehicles, electric equipment, and so forth.