Nanomaterials to Combat NOx Pollution

The presence of NOx gases (NO-F-NO2) in the atmosphere is a major concern of society because of their associated adverse and harmful effects. In order to remove the NOx gases from the air, photocatalysis arises as an innovative and promising technique. Through the use of photochemical oxidation processes the NOx and NO2 gases are oxidised to NO3- form and thus removed from the air. In recent years new nanomaterials are being developed by researchers with the aim to enhance their photocatalytic activity to combat the NOx pollution. The main focus is devoted to preparing new TiO2 based compounds with the highest specific surface area (SSA), different morphology and chemical modifications. In order to increase the SSA, different substrates were used to disperse the TiO2 nanoparticles: organic and carbon fibres, mesoporous materials, clays composites and nanoporous microparticles. In the other hand, high photocatalytic performances were obtained with nanotubes, self-orderer nano-tubular films and nanoparticles with the lowest size. Conversely, when TiO2 is doped with ions the oxide exhibited a better photocatalytic performance under visible light, which is related to the creation of intermediate energy states between the conduction band and the valence band. Alternatively, visible light photocatalysts different from titanium oxide have been studied, which exhibit a good De-NOx efficiency working under lambda > 400 nm visible light irradiation.