Preparation of super-hydrophobic hollow silicon dioxide and titanium dioxide cooling coatings and their application as green building materials

To solve the limitations of radiation cooling coating materials, many researches focus on the optical characteristics of materials rather than the coating material structure. Herein, super-hydrophobic hollow silicon dioxide/titanium dioxide (H-SiO₂@TiO₂) microspheres with large size (10 μm) and small size (1 μm) are prepared using polystyrene microsphere templates. H-SiO₂@TiO₂ radiation cooling coating (HSTC) are prepared by integrating with epoxy resin. Effects of mass ratio of H-SiO₂@TiO₂ with two sizes on the radiation cooling performance, surface roughness and hydrophobicity are investigated. HSTC (50 wt.% of 10 μm particle and 50 wt.% of 1 μm particle) presents the highest surface roughness with <i>R</i>_<i>a</i> of 148 nm and <i>R</i>_<i>q</i> of 180 nm. Good optical properties (<i>R</i>_<i>solar</i> = 97.6%, <i>ε</i>_<i>LWIR</i> = 96.3%) are achieved due to complementary optical properties of SiO₂ and TiO₂. Cooling effects of 4°C~5°C under daytime and 6°C~7°C at night are exhibited. Maximum contact angle of HSTC is 159.6° and maintained &gt; 150° after being soaked in solutions with different pH for 7 days, exhibiting an excellent corrosion resistance. HSTC can effectively reduce the cooling load of buildings via energy consumption simulation. This study paves a way for preparing advanced radiation cooling coating materials in the construction field.