Superhydrophobic daytime radiative cooling coating incorporated with phase change microcapsules for building thermal regulation

Passive daytime radiative cooling (PDRC) is a non-consumptive and non-polluting cooling technology. As well as reflecting sunlight, it can also cool surfaces by emitting heat into space. A daytime radiative cooling coating with both phase change energy storage (PCES) function and self-cleaning performance was prepared by using polydimethylsiloxane (PDMS) as a binder and phase change microcapsules (PCMs) as filler. The PCMs-SiO₂/PDMS coating has a solar reflectivity larger than 90% and an infrared emissivity greater than 94%. The coating exhibited PDRC temperature of 13.07 °C in summer and 5.54 °C in autumn, respectively. In addition, the PCMs-SiO₂/PDMS coating exhibits significant temperature hysteresis due to their unique PCES function and thus reducing temperature fluctuation. Furthermore, the self-cleaning properties of the PCMs-SiO₂/PDMS coatings protected the surface from contamination, allowing the coatings to maintain their RC effect during long-term outdoor use. Moreover, the coating maintained excellent optical properties after chemical corrosion, ultraviolet aging, and mechanical friction, providing a promising prospect for practical applications.