Synergistic TiO2/VO2 Window Coating with Thermochromism, Enhanced Luminous Transmittance, and Photocatalytic Activity

Modern buildings tend to be "energy guzzlers" and have indoor environments with unhealthy air. Glazing with TiO2/VO(2 )bilayer coatings (1) exhibits enhanced photocatalytic air purification compared with single-layer TiO2 due to heating from the underlying infrared-absorbing VO2 film, (2) is thermochromic thanks to the VO2 and admits less solar energy inflow when there is a cooling demand, and (3) has significantly improved luminous transmittance as a result of antireflection due to TiO2. These 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 TiO2NO2 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 which exploits spectral-selective material properties for solar illumination.