Promotion of photocatalytic activity onto building facades through the application of TIO2 based nanolayers

Abstract

Urbanism and communities centralization enlarges atmospheric pollution decreasing the health quality of human beings and affects the aesthetical appearance building’s façades. Apart from health related consequences, pollution leads to façade soiling and staining that represent considerable maintenance costs and structures degradation. Consequently, metropolitan planners face the concern of increasing functional housing spaces forecasting at the same time the application of sustainable construction concepts. The application of a heterogeneous photocatalysis has been pointed as a potential technology to be applied for self-cleaning and de-pollution solutions. Photocatalytic activities arise from the photocatalytic properties of employed semiconductor materials. Titanium dioxide nanocoatings are, by fare, the widely used as a consequence of its powerful oxidation strength, chemical stability, non toxic properties and availability. Although there is a considerable number of techniques to deposit TiO2 based materials, few of them have potential market application for civil construction industry. For this particular application prototype scale up may be as smooth as possible with relative small implementation costs. In this sense, the deposition of TiO2 nanoparticles (TiO2-NNPs) using liquid based techniques (e.g. spin coating and/or dip coating) may be a feasible solution to produce facade’s materials with self-cleaning and de-polluting abilities. Moreover, it is consensual in scientific community that the presence of anatase phase enhances photocatalytic activity of coated materials. Furthermore, the formulation of solutions using TiO2-NNPs with bulk anatase crystalline structure will eliminate the heat treatment step generally required to achieve it. In this study, TiO2 nanoparticles based layers were deposited onto different ceramic materials using dip-coating and magnetron sputtering method.s The colourless layers were deposited onto gray and white ceramic substrates without changing their aesthetical appearance. The photocatalytic activity (degradation of pollutants adsorbed on the surface) of the TiO2-NNPs based layers was characterized via the decomposition rate of an aqueous solution of Methylene blue (MB) under UV light irradiation. The highest photocatalytic performance was achieved for the coated gray ceramics; a photodegradation rate of and a photocatalytic efficiency of 83% was found. The mentioned coated sample allowed the attainment of a moderate self-cleaning ability and a noticeable photodegradation capacity.