The Effect of Interfacial Chemical Bonding in TiO(2)-SiO(2) Composites on Their Photocatalytic NOx Abatement Performance

The chemical bonding of particulate photocatalysts to supporting material surfaces is of great importance in engineering more efficient and practical photocatalytic structures. However, the influence of such chemical bonding on the optical and surface properties of the photocatalyst and thus its photocatalytic activity/reaction selectivity behavior has not been systematically studied. In this investigation, TiO(2) has been supported on the surface of SiO(2) by means of two different methods: (i) by the in situ formation of TiO(2) in the presence of sand quartz via a sol-gel method employing tetrabutyl orthotitanium (TBOT); and (ii) by binding the commercial TiO(2) powder to quartz on a surface silica gel layer formed from the reaction of quartz with tetraethylorthosilicate (TEOS). For comparison, TiO(2) nanoparticles were also deposited on the surfaces of a more reactive SiO(2) prepared by a hydrolysis-controlled sol-gel technique as well as through a sol-gel route from TiO(2) and SiO(2) precursors. The combination of TiO(2) and SiO(2), through interfacial Ti-O-Si bonds, was confirmed by FTIR spectroscopy and the photocatalytic activities of the obtained composites were tested for photocatalytic degradation of NO according to the ISO standard method (ISO 22197−1). The electron microscope images of the obtained materials showed that variable photocatalyst coverage of the support surface can successfully be achieved but the photocatalytic activity towards NO removal was found to be affected by the preparation method and the nitrate selectivity is adversely affected by Ti-O-Si bonding.