Photocatalysis has been used not only in water and air treatment but also, increasingly, in various domains such architecture (self-cleaning glass, tiles, cement), sanitation (clean room wall paint) and the PV industry. The use of protective coatings for photovoltaic glazing represents a hot topic at EU level, as an alternative method to increase the electrical output. One challenge is to simultaneously meet the requirements for photocatalytic self-cleaning properties and the specific optical properties in the full solar spectral range: high transmittance (T%) - low reflectance (R%) in UV-Vis and low T% - high R% in IR (IR-shielding properties).
Following the optical and the self-cleaning pre-requisites, a novel, sol-gel composite using WO3 and reduced graphene oxide (r-GO) was obtained. Tungsten precursors (WCl6, WOCl4 or H2WO4) along with r-GO (0 - 5% wt.) were dispersed in water-ethanol mixtures (ratios of 1:0, 0:1 and 1:1). Acetylacetone and SDS were used at concentrations higher and lower than the critical micelle concentrationto control particle nucleation and growth. The sols were aged for 48 h, dried and annealed at 550oC. The synthesis parameters were correlated with the crystallinity, morphology, surface energy and optical properties of the powders. Stable dispersions were prepared using the powders with high TUV-Vis - low TIR and chitosan, to be sprayed on glass and solar glass. The results show that homogeneous, transparent thin films can be obtained using dispersions at optimized pH and concentration; the number of spraying sequences and the deposition temperature (40 - 60oC) are the key parameters in controlling the optical and self-cleaning properties. Promising photocatalytic efficiency values in phenol removal under simulated solar radiation (85% Vis and 15% UV) were obtained for the composite thin films, with the rGO outlining that this supports the increased charge separation.