Highly porous thermochromic VO2-SiO2 composite aerogel with enhanced visible transparency, thermal insulation and stability for energy-saving windows

Highly porous VO 2 -SiO 2 composite aerogels were in-situ prepared via CO 2 supercritical drying. • The VO 2 -SiO 2 aerogel films exhibited high sunlight modulation and thermal insulation performance. • The VO 2 -SiO 2 aerogel can be used for smart windows due to its thermochromism/thermal insulation synergy and good durability. Vanadium dioxide (VO 2 ) shows great potential for applications in smart windows due to its reversible metal-insulator phase transition and unique thermochromism, but its low visible transparency and poor stability require further improvement, and low thermal conductivity is vital for energy-saving windows. Herein, a thermochromic VO 2 -SiO 2 composite aerogel with high thermal insulation and high stability was in-situ synthesized via sol-hydrothermal and CO 2 supercritical drying process. The results demonstrate that the VO 2 -SiO 2 composite aerogels possess a highly porous structure, with a large pore volume ranging from 1.44 to 2.15 cm 3 /g and an average pore diameter of 11.24-19.00 nm. The as-prepared VO 2 -SiO 2 aerogel/PMMA composite films with V/Si molar ratio of 3 exhibit the highest solar modulation ability (Δ T sol  = 12.84%) and at 90°C, exhibits a surprising increase in visible light transmittance, reaching the highest value of 48.87%, which is 4.49% higher than that at 20°C. Moreover, the thermal insulation performance test results indicate that all the composite aerogel films exhibit good thermal insulation performance, and maintain excellent thermal stability after 30 cycles of thermal insulation tests. This study presents a novel strategy for fabricating VO 2 -SiO 2 composite aerogels, which can fully exploit the synergistic effect between VO 2 and SiO 2 aerogels, showing great application potential for energy-saving windows. Download: Download high-res image (365KB) Download: Download full-size image