Poisoning prevention of TiO2 photocatalyst coatings sputtered on soda-lime glass by intercalation of SiNx diffusion barriers

Facile process to greatly improve the photocatalytic activity of the TiO 2 thin film on window glass for the photodegradation of acetone and benzene

“…Among them, sol-gel process is the most prevailing one because it's operated at mild conditions and can be easily scaled up to fabricate large-sized TiO 2 thin film [18]. However, it has been reported that the TiO 2 thin film fabricated on window glass via the traditional sol-gel method had very low photocatalytic activity [3,[19][20][21], hindering its practical application. Because usually the obtained TiO 2 thin film on window glass has poor crystallinity, which is caused by the thermal diffusion of sodium ions from glass substrate into TiO 2 thin film during calcination [19,20].…”

“…Several methods have been proposed to solve this problem, most of them focused on preventing the thermal diffusion of sodium ions, such as inserting a SiO 2 or SiN x barrier layer between window glass and TiO 2 thin film [21], and using borosilicate or quartz glass which contains few sodium ions as substrate [3,22]. However, there are some disadvantages of these methods, the former increases the complexity of fabrication process which raises up total cost, the latter employs more expensive borosilicate or quartz glass instead of cheap and widely applied sodalime glass (window glass), which also greatly increases total cost.…”

Effect of SiNx diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol–gel dip coating and reactive magnetron sputtering

“…Usually, TiO 2 is amorphous when deposited at low temperature [5–6]. Heat treatment at a higher temperature (around 450 °C) is usually required in order to obtain the photoactive anatase phase.…”

“…The poisoning effect of the Na + ions on the photocatalytic activity occurs in different ways and depends on their concentration, for example: (a) Na + ions increase the temperature of anatase formation and increase the particle size [4,7], (b) Na + ions inhibit the formation of the anatase phase and act as a recombination center of photo-generated electron–hole pairs [3], and (c) Na + ions induce the formation of brookite or sodium titanate (Na 2 O x TiO 2 ), which is less photoactive than the anatase form [8]. In order to prevent this poisoning effect, various strategies have been reported including ion exchange via the formation of a thin proton-exchanged surface layer [3] or a post-treatment of the TiO 2 films by hydrochloric acid [9], and the usage of a diffusion barrier intercalated between the substrate and the TiO 2 film [6,10]. The most widely used diffusion barriers are SiO 2 [10–11] and SiN x [6] layers.…”

“…In order to prevent this poisoning effect, various strategies have been reported including ion exchange via the formation of a thin proton-exchanged surface layer [3] or a post-treatment of the TiO 2 films by hydrochloric acid [9], and the usage of a diffusion barrier intercalated between the substrate and the TiO 2 film [6,10]. The most widely used diffusion barriers are SiO 2 [10–11] and SiN x [6] layers. SiN x diffusion barriers show better efficiency than SiO 2 with respect to inhibition of the diffusion of Na + ions [6].…”