Nanomaterials to Combat NO_X Pollution

Abstract

The presence of NO9x) gases (NO+NO2) in the atmosphere is a major concern of society because of their associated adverse and harmful effects. In order to remove the NO(x) gases from the air, photocatalysis arises as an innovative and promising technique. Through the use of photochemical oxidation processes the NO 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 NO(x) 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-NO(x) efficiency working under λ > 400 nm visible light irradiation.

Advances in photocatalytic NOx abatement through the use of Fe2O3/TiO2 nanocomposites

“…45 In this work, beyond the structural, compositional and morphological characterization, the photocatalytic NO x abatement performances of Fe 2 O 3 /TiO 2 nanocomposites are presented, with particular attention to the release of toxic intermediates into the outer atmosphere. 48 Remarkably, the obtained systems display a high NO x removal efficiency, superior to that evaluated for Degussa P25 and other modied TiO 2based materials. 1,3,49…”

“…The complete oxidation of NO to nitrate or nitric acid (NO 3 À /HNO 3 ) is a complex process, that involves several intermediate species. 48,61,62 Basically, the mechanism entails several one-electron transfer steps, via nitrous acid (HNO 2 ) and nitrogen dioxide (NO 2 ) as intermediate species. The in situ generated reactive oxygen species (mainly hydroxyl radicals but also superoxides; see also below and ESI Fig.…”

Development of Multifunctional Coatings for Protecting Stones and Lime Mortars of the Architectural Heritage

“…In the case of the heterostructures, this shift is more obvious for the TiO 2 -ZnO 50/50 sample and this finding can be related to the higher number of heterojunctions formed in these nanoparticles as a consequence of the stoichiometry of the raw materials. The key of photocatalysis is the participation of reactive oxygen species (ROS) in the chemical oxidative processes (Balbuena, Cruz-Yusta and Sánchez 2015). Thus, it results of interest to know the ability of the samples here studied to produce ROS species.…”

Scalable Synthesis of Mesoporous TiO2 for Environmental Photocatalytic Applications

“…In this context, water resources are gaining increasing attention due to the occurrence of emerging pollutants including dyes, pharmaceutical and personal care products, endocrine disruptors, pathogens [1,2]. Moreover, the increasing amount of atmospheric pollutants has been regarded among the main causes of respiratory diseases such as emphysema, and bronchitis arising from the contact of NO x with lungs [3].…”