High activity of brookite TiO2 nanoparticles in the photocatalytic abatement of ammonia in water

The effects of the TiO2 crystal structure and its surface modification with Pt nanoparticles on the photocatalytic oxidation of NH3 in the aqueous phase were studied with home-made TiO2 photocatalyst powders synthesized by a thermo-hydrolysis approach that allowed a fine control of the crystallographic phase composition. Ammonia conversion and the selectivity toward mildly oxidized N2 and highly oxidized nitrite and nitrate anions were monitored during the runs. Pure brookite powders modified by Pt nanoparticles, deposited either from a colloidal suspension or by deposition-precipitation, were found to be the most efficient photocatalysts in NH3 degradation, with a desired good selectivity toward innocuous N2. The photo-activity in NH3 oxidation was correlated to the crystallographic features of the investigated TiO2-based materials, also taking into account the effects induced on the reaction paths by the presence of Pt nanoparticles on TiO2.