Thermo-regulating cellulose aerogel-based composite PCM with enhanced hydrophobicity and energy storage density for building envelope applications

The thermal performance of building envelopes directly influences energy consumption, highlighting the importance of developing novel passive temperature-regulating functional materials. Phase change materials (PCMs) have gained attention for their high thermal energy storage capacity, yet leakage issues hinder their building applications. Cellulose aerogels, with high porosity, low density, and a three-dimensional nanoporous structure, are considered ideal matrices for encapsulating PCMs. However, their inherent hydrophilicity limits long-term stability, and both PCM encapsulation efficiency and phase change enthalpy need enhancement. To overcome these challenges, this study employed methyltrimethoxysilane for hydrophobic modification, achieving a water contact angle >120°, and dopamine hydrochloride for amination, reaching 93.8% encapsulation efficiency in the composite PCM. The dually modified aerogel (MD-CNF) was combined with a binary PCM (lauryl alcohol-stearic acid, LASA) to fabricate MD-CNF/LASA. Results show that MD-CNF/LASA exhibits a high phase change enthalpy of 178.3 J/g, with a 25.7-fold increase in thermal energy storage coefficient over pure MD-CNF, demonstrating excellent heat absorption and release. Under identical heating, its cold-side temperature was 31.1% lower than MD-CNF, with a 10.6 °C difference and delayed peak temperature time. Therefore, MD-CNF/LASA shows great potential for building envelopes to enhance indoor thermal comfort while reducing energy use and carbon emissions.