Photocatalytic building products: innovation and experimentations

Facing air pollution in large urban areas is one of the great challenges in health and environment protection. The use of photocatalytic products (Kaneko, 2002; Fujishima, 1999) may be an answer to such an issue. The main feature of these products, which generally contain titanium dioxide photocatalyst, lies in the ability to exploit both solar and suitable artificial light to induce chemical reactions which cause the destruction of surface adsorbed pollutants. This allows the removal of air pollutants and of organic compounds which would otherwise cause the progressive deterioration of buildings. The use of photocatalytic materials in confined environments may lead to an improvement of air quality in domestic, working and school environments, by the reduction of both organic and inorganic compounds (mainly converted to carbonic anhydride and inorganic salts, respectively), and of particulate (PM10 and PM2,5). In order to obtain the best performance from the photocatalytic finishing, it is necessary to consider practical aspects such as room lighting, type and distance of the light sources, and air humidity as well. The work presented here is being performed within the framework of a research project of the University of Padova, named "Nanotechnologies for the building trade. New photocatalytic materials based on metal systems-modified titanium dioxide. Application to cement and glass-based materials. Technological tests and fields of use for the proposed innovative materials". The issues involved in the project are as follows: (i) building-up simple tests and devices able to yield quantitative data about photodegradation both in solution and in gaseous systems, starting from the most common commercial titanium dioxide product (P25); (ii) widening the light frequency range able to induce the photocatalytic process through doping of titanium dioxide (especially with N), and the subsequent preparation of the product as a nanopowder by means of a simple and inexpensive method; (iii) measuring the degradation effectiveness towards several pollutants, and studying the influence of the host matrix; (iv) testing different light sources for indoor applications; (v) verifying the effectiveness of other useful surface properties such as self-cleaning and bactericide action.