TiO ₂/VO ₂ Bilayer Coatings for Glazing: Synergistically Enhanced Photocatalytic, Thermochromic, and Luminous Properties

Abstract

Modern buildings tend to be energy guzzlers and have indoor environments with unhealthy air. Glazing with TiO₂/VO₂ bilayer coatings (i) exhibits enhanced photocatalytic air purification compared to single-layer TiO₂ due to heating from the underlying infrared-absorbing VO₂ film, (ii) is thermochromic thanks to the VO₂ and admits less solar energy inflow when there is a cooling demand, and (iii) has significantly improved luminous transmittance as a result of anti-reflection due to TiO₂. The coatings were deposited by reactive DC magnetron sputtering onto heated glass; they were nanocrystalline and the anatase phase prevailed in TiO₂. The VO₂ coatings showed well-developed thermochromism. The photocatalytic degradation rate of stearic acid was almost doubled for the TiO₂/VO₂ bilayer film compared with that for single-layer TiO₂. Our results demonstrate an important, and hitherto unexplored, synergy between photocatalysis, thermochromism, and high luminous transmittance exploiting spectral selective material properties for solar illumination.

Keywords: photocatalysis, thermochromism, titanium dioxide, vanadium dioxide, energy efficient coatings, indoor air cleaning