Multifunctional silica aerogel-infused paint for self-cleaning and radiative cooling

Massive energy is consumed to cool buildings for comfortable life in hot climates due to indoor air-conditioning, which necessitates the passive daytime radiative cooling of buildings. Given the high ambient temperature, it is essential to increase the thermal resistance of building walls through paints and enhance their durability to dust and aerosol contamination. In this work, a multifunctional composite paint, mainly consisting of inorganic pigments and mesoporous silica aerogel (SA), is proposed for passive radiative cooling, low thermal conductivity, and surface self-cleaning. In comparison with ordinary paint, the SA microparticles-infused composite paint can enhance the reflectance (ρ_VIS-NIR) to the solar irradiance by up to 15% in the visible and near-infrared ranges (0.3–2.5 μm). It also maintains the radiative cooling property with about 0.96 emissivity (ε_LWIR) in the atmospheric transparency windows (8–13 μm) for thermal radiation to dissipate into the cold outer space. Even after long-term outdoor exposure to harsh environmental conditions, SA-infused white paint can still maintain its spectral and wetting properties, achieving daytime cooling with 7.4 °C lower than the ambient temperature. Moreover, the SA infusion enables the paint to reduce the thermal conductivity by 50% and provide much better thermal insulation, while SA renders the paint surface hydrophobic and self-cleaning.