Preparation and performance study of “degradation-heat insulation” multifunctional coatings based on TiO ₂ /SiO ₂ composite aerogels

In response to the dual challenges of indoor air pollution control and building energy efficiency, a multifunctional indoor coating exhibiting both high formaldehyde degradation and excellent thermal insulation properties has been developed. This coating incorporates self-synthesized TiO2/SiO2 composite aerogels as functional fillers. The study systematically explores the role of these aerogels in enhancing the performance of the coating and elucidates their synergistic mechanisms. The optimal formulation (C3) exhibits remarkable mechanical and durability properties, including a 0-level adhesion, 5H hardness, low surface roughness (Ra = 1.42 μm, maximum peak-to-valley height difference Dif = 14 μm), and robust resistance to water, acid, and base. Furthermore, it achieves a thermal conductivity as low as 0.267 W/m · K and a thermal insulation temperature difference of 23.9 °C, along with a formaldehyde degradation rate of 83.6% after 6 hours of UV light exposure. Correlation analysis revealed a strong positive correlation (r ≈ 0.96) between the TiO2/SiO2 composite aerogel content and degradation performance, indicating its dominant role in photocatalytic degradation. Thermogravimetric analysis further confirmed that increasing the TiO2/SiO2 composite aerogel content enhances the thermal stability of the coating, with the Z3 formulation maintaining a carbon residue of 74.8% at 800 °C.