Construction of Uniform Thermal Network in Passive Radiative Cooling Coatings by Nanocellulose-Mediated Pickering...

Developing high-performance passive radiative cooling coatings (PRCC) with high thermal conductivity for fast heat dissipation from self-heating objects remains a significant challenge. In this study, a nanocellulose-mediated Pickering emulsion strategy was employed to construct a uniform hexagonal boron nitride (BN) thermal network within PRCC. Benefiting from the Pickering emulsion template stabilized by TEMPO-oxidized cellulose nanofibrils (TOCNF), BN nanosheets and other functional inorganic nanoparticles were uniformly dispersed in the PRCC matrix, forming a continuous and homogeneous thermally conductive network. This structural design endowed the PRCC with excellent thermal conductivity, high solar reflectance in the solar spectrum (0.3-2.5 μm), and strong emissivity in the "atmospheric window" (ATSW, 8-13 μm). Specifically, the thermal conductivity of the TOCNF-BN-modified PRCC reached 2.28 ± 0.15 W·m^-1·K^-1, which was significantly higher than that of the pristine PRCC. The coating exhibited a solar reflectivity of ~87% and an emissivity of ~93% in the ATSW. Outdoor model temperature tests indicated that the internal temperature of the PRCC-TOCNF-BN-coated metal cabinet was 9.6 °C lower than that of the bare cabinet and 6.7 °C lower than the cabinet coated with pristine PRCC. This novel approach of using Pickering emulsion templates to fabricate highly thermally conductive radiative cooling coatings provides a new strategy for the development of high-performance and multifunctional radiative cooling materials for thermal management applications.