Silica nanoparticle-reinforced cellulose aerogels with enhanced thermal stability for efficient thermal insulation

To maintain comfortable indoor conditions, energy consumption associated with building operation accounts for a substantial proportion of global energy use. To effectively reduce building energy demand, it is crucial to develop high-performance thermal insulation materials that can be integrated with building envelope structures. However, simultaneously achieving low thermal conductivity, hydrophobicity, and improved thermal stability in cellulose-based aerogels remains a major challenge. In this work, cellulose aerogels with outstanding thermal insulation properties were fabricated and further modified by surface hydrophobic treatment with 1H,1H,2H,2H-perfluorooctyltriethoxysilane and incorporation of silica sol to overcome the intrinsic strong hydrophilicity and limited thermal stability of cellulose aerogels. The resulting PTCNF/Si composite aerogels showed excellent hydrophobic properties, with high water contact angles (122-129°), while maintaining low thermal conductivities of approximately 24-26 mW (m K)^-1, indicative of good thermal insulation performance. In terms of thermal stability, the PTCNF/Si-1.5 composite aerogel containing 1.5 mL of silica sol showed a char residue yield of 58.8 wt% at 800 °C, which was significantly higher than that of the pure TCNF aerogel. Overall, the hydrophobic PTCNF/Si composite aerogels combine low thermal conductivity with enhanced thermal stability and therefore hold promising potential as functional thermal insulation materials for energy-efficient building envelopes.