Auto-Deposited Microparticle Composite Coating for Low-Cost and Efficient Daytime Radiative Cooling

Radiative cooling is an excellent strategy for mitigating global warming, by enhancing heat fluxes away from the Earth, thus balancing the Earth's heat flow. However, for randomly particle-dispersed radiative cooling materials, the particle content as high as 94-96 wt % or 60 vol %, far exceeds the critical pigment percentage (40-50%) of traditional coatings, preventing its large-scale application. Here, inspired by particle deposition under gravity in solution, we demonstrate an auto-deposited SiO₂ composite radiative cooling coating (ADRC) which reduces the amounts of particles required and lowers costs. This particle density gradient structure enhances the local volume fraction of particles, thereby the coating exhibits high solar reflectance (93%) and infrared emissivity (89%), contributing to a daytime subambient temperature drop of 12 °C. The cooling energy-saving potential of buildings in China utilizing the ADRC as roofs ranges from 6.42 to 13.52%. This low-cost and scalable radiative cooler is expected to reduce energy consumption and carbon emissions, addressing global warming issues.