3D mesoporous structure assembled from monoclinic M-phase VO2 nanoflakes with enhanced thermochromic performance

Abstract

Monoclinic M-phase VO2 is a promising candidate for thermochromic materials due to its abrupt change in the near infrared (NIR) transmittance along with the metal-to-insulator transition (MIT) at a critical temperature ∼68 °C. However, low luminous transmittance (Tlum), poor solar energy modulation ability (ΔTsol), and high phase transition temperature (Tc) can limit the application of VO2 for smart windows. To overcome these limitations, 3D mesoporous structure can be employed in VO2 films. Herein, 3D mesoporous structures assembled from monoclinic M-phase VO2 nanoflakes with a pore size of about 2–10 nm were synthesized by a hydrothermal method using Ensete ventricosum fiber (EF) as a template followed by calcination at 450 °C. The prepared film exhibited excellent thermochromic performance with balanced Tlum = 67.3%, ΔTsol = 12.5%, and lowering Tc to 63.15 °C. This is because the 3D mesoporous structure can offer the uniform dispersion of VO2 nanoflakes in the film to enhance Tlum, ensure sufficient VO2 nanoflakes in the film for high ΔTsol and lower Tc. Therefore, this work can provide a green approach to synthesize 3D mesoporous structures assembled from monoclinic M-phase VO2 nanoflakes and promote their application in smart windows.