Bacterial cellulose based three-dimensional porous composites with remarkable amphiphobic monolith properties for passive daytime radiative cooling

Abstract

To tackle the daytime radiative cooling performance (DRCP) degradation of passive daytime radiative cooling materials (PDRCMs) due to contamination from aqueous or oily contaminants, modified three-dimensional porous composites of bacterial cellulose (BC) and barium sulfate (BaSO4) were fabricated by a unidirectional freeze-casting process and silanization modification. The modified BC/BaSO4 (M−BC/BaSO4) composites exhibited average reflectivity of 97.75%, average emissivity of 95.74%, and remarkable amphiphobic monolith properties with a water contact angle (WCA) and oily contact angle (OCA) of 154° and 145.5° for the surface and those of 153.5° and 143.5° for the internal section, respectively. They also exhibited insignificant changes in the DRCP before and after self-cleaning, achieving an average and maximum temperature drop of 10.40°C and 16.38°C before self-cleaning and those of 9.92°C and 16.40°C after self-cleaning, respectively. This work provides a new strategy for sustainable PDRCMs in practical applications.