Hydrophobic magnesium silicate hydroxide coating for daytime radiative cooling

Daytime radiative cooling (DRC) offers a promising alternative to conventional electrical cooling for subambient cooling without additional energy consumption or environmental pollution. Nonetheless, the key challenge facing current DRC systems is complex and stringent surface designs, hampering their large-scale applications. Herein, we propose a cost-effective and straightforward approach to fabricate a single-component Mg 3 [Si 2 O 5 ](OH) 4 (MSH) coating on ceramic substrate, with the MSH powder showing a broad particle size distribution (0.35–1.95 μm), a wide band gap (4.45 eV), and sufficient solar reflectance (95.0 %) and thermal emissivity (94.1 % in the 8–13 μm atmospheric transparency window); a 200-μm-thick dense MSH coating further exhibits exceptional emissivity in the atmospheric transparency window (97.6 %) while maintaining adequate solar reflectance (94.4 %) and thermal conductivity (1.786 W·m −1 ·K −1 ), demonstrating remarkable DRC performance. Outdoor testing yields a subambient cooling of 8.2 °C and a radiative cooling power of 94.5 W·m −2 under 511.1 W·m −2 solar irradiance. Such a novel DRC coating with superior hydrophobicity and environmental durability not only provides effective protection to ensure the long-term sustainability of its DRC performance, but also opens up a promising pathway for the development of high-performance radiative cooling materials, thereby facilitating its practical sustainable applications for effective thermal management.