Self-Cleaning and Anticorrosive Silica Microsphere@Boron Nitride Nanosheets Core-Shell Hierarchical Structure for Highly Efficient Passive Radiative Cooling.

Abstract

Passive radiative cooling is a promising technology that can achieve high-efficient cooling by reflecting solar radiation while simultaneously emitting heat without consuming energy. However, to precisely construct the microstructure of the materials is crucial to maximize their performance. Herein, a self-cleaning and anticorrosive 3D silica microsphere@boron nitride nanosheets core-shell hierarchical structure (SiO2@BNNSs) stacked coating is fabricated on the surface of aluminum oxide substrate. The cooperative integration of prominently sunlight reflective BNNSs and highly selective infrared emissive SiO2 microspheres, combined with sunlight scattering brought by the 3D interconnecting configuration, results in an outstanding solar radiation reflectance of 0.84 and a mid-infrared emittance of 0.82 for the SiO2@BNNS coating. These features enable the SiO2@BNNS coating to exhibit excellent passive radiative cooling performances with high temperature drop of ≈17.5°C on sunny day and ≈8.1°C on overcast day, respectively. More importantly, the SiO2@BNNS coating also exhibits self-cleaning performance and corrosion resistance in both acidic and alkaline conditions, ensuring the preeminent stability over a long time for various practical applications. This work demonstrates that the hybridization of the high reflection, scattering, and emittance of different materials through reasonable structure design can achieve high-efficient passive radiative cooling, offering promising prospect for energy-saving cooling technology.