Fabrication of multifunctional coating which combines low-e property and visible-light-responsive photocatalytic activity

Abstract

A novel multifunctional glazing which combines low-emissivity (low-e) properties and visible-light-responsive photocatalytic activity is proposed. One characteristic point is that it is composed of a simple two-layer coating of F-doped SnO 2 (SnO 2:F) as an inner layer and titanium dioxide (TiO 2) as an outer layer. We confirm that SnO 2:F and TiO 2 coatings add the low-e property and the photocatalytic activity, respectively. Another characteristic point is that the outer TiO 2 layer has a visible-light-responsive photocatalytic activity. A simultaneous irradiation processing of H and N ions onto the TiO 2 films is presented to dope with N atoms substitutionally and modify its photocatalytic activity. We find that the co-irradiation with H and N ions of 0.2 keV onto the TiO 2 surface improves the photocatalytic activity under visible-light (λ⩾370 nm) illumination by more than three times compared to that of non-irradiated samples. However, the photocatalytic activity under ultraviolet-light (λ⩾200 nm) illumination becomes worse by increasing the ion-acceleration energy. Very low ion-acceleration is the key to dope N atoms into TiO 2 films substitutionally by reduction and diffusion processes as well as to suppress a preferential sputtering of oxygen.