BiOBr photocatalyst with high activity for NOx elimination

Abstract Bismuth oxybromide (BiOBr) was synthesized in aqueous medium in presence of EDTA as structure-directing agent following a simple coprecipitation method at 23 °C and by microwave irradiation at 110 °C. The physicochemical properties of BiOBr (morphology, specific surface area, energy band gap and photocatalytic activity) were modified using different EDTA concentrations. Nanoparticles of BiOBr with {1 1 0} crystallographic exposed facets were obtained as a peculiar feature of the synthesis followed. The photocatalytic activity of BiOBr was evaluated in the oxidation reaction of nitric oxide (NO) in gaseous phase under UV–Vis and visible irradiation. An enhancement in the NO conversion degree was reached for BiOBr synthesized by coprecipitation with an EDTA/Bi molar ratio of 0.6. This sample showed a NO conversion degree of 94%, a selectivity to nitrate ions of 98%, a good stability after four cycles of irradiation and sample was able to retain its high photocatalytic activity under humidity conditions (70% RH). The use of different chemical scavengers revealed that superoxide radical (O2•-) was the main reactive specie in the mechanism of the photocatalytic reaction. BiOBr photocatalyst was successfully incorporated in two formulations of ceramic coatings to develop prototypes of building materials with active surface for the photocatalytic elimination of NOx gases from the air.