Br vacancy engineering in Cs 3 Bi 2 Br 9 for photocatalytic NO oxidation under visible light.

Photocatalysis using the visible light of the sun is an environmentally friendly method of eliminating the NOx pollutant from the ambient air. Although Cs 3 Bi 2 Br 9 , a semiconductor with a band gap of 2.54 eV, may be a strong absorber of visible light, its photocatalysis towards the abatement of NOx is unknown. In this study, Cs 3 Bi 2-x Pb x Br 9-x (0 ≤ x ≤ 0.0789) are used for the photocatalytic oxidation of NOx. A significant NO oxidation efficiency (80%) is observed over Cs 3 Bi 2-x Pb x Br 9-x (x = 0.0443) under visible light, which is attributable to the Br vacancy (V Br ) brought about by Pb 2+ doping. The presence of V Br increased the ionic selectivity of in the oxidized NO. At higher Pb doping level, two HONOs adsorbed on the V Br , linked, and then reduced by hot electrons to produce N 2 O 2 2- . The di-azo coupling could passivate the activation of NO on the V Br . This work advances the defect engineering of halide for the photo-driving solid-gas reaction in air.