Fluorine-free super-hydrophobic barium sulfate particles for passive daytime radiative cooling

• Fluorine-free super-hydrophobic BaSO 4 particles for radiative cooling were obtained. • M−BaSO 4 particles showed negligible spectral changes and good thermal stability . • M−BaSO 4 particles exhibited a certain ability to ultraviolet aging resistance. To enhance the application of barium sulfate (BaSO 4 ) particles in passive daytime radiative cooling (PDRC), we developed a simple fluorine-free hydrophobic modification method for BaSO 4 particles using hexadecyl trimethoxy silane (HDTMS) under mild conditions. The modified BaSO 4 (M−BaSO 4 ) particles exhibited super-hydrophobicity with a water contact angle (WCA) of 165.6 ° and enhanced dispersibility. M−BaSO 4 particles showed negligible changes in spectral properties compared to BaSO 4 particles, maintaining their suitability for PDRC. Furthermore, HDTMS exhibited the potential to hydrophobically modify both BaSO 4 and SiO 2 particles simultaneously. This work provides a promising fluorine-free hydrophobic modification strategy to broaden the applications of BaSO 4 particles in PDRC.