ABSTRACT The integration of superhydrophobicity and passive daytime radiative cooling is highly desirable for advanced thermal management of outdoor electronics, yet achieving it via a facile approach remains challenging. Herein, MgO@BN powder (MgO particles coated with a BN shell) with a micro‐nano hierarchical structure was synthesized via in situ combustion synthesis. By adjusting the MgO diluent content, the optical properties and hydrophobicity were effectively tailored. Increasing the MgO content was found to enhance both solar reflectance (0.3–2.5 µm) and infrared emissivity (8–13 µm), while reducing the water contact angle, indicating a trade‐off between optical performance and surface wettability. At an optimal content of 3 mol MgO, the powder achieved an average solar reflectance of 85.9%, an infrared emissivity of 84.9%, and a water contact angle of 136.7° ± 1.2°. The coating prepared with this powder as filler exhibited remarkable superhydrophobicity (CA = 151.5° ± 0.8°) and excellent self‐cleaning performance. Under simulated solar irradiation of ∼880 W/m 2 on a transformer model, the coating provided an internal temperature reduction of 7.2°C, demonstrating its outstanding radiative cooling capability and potential for ensuring the stable operation of outdoor electronics.
Meng et al. (Wed,) studied this question.