Photocatalytic NO removal over defective Bi/BiOBr nanoflowers: The inhibition of toxic NO2 intermediate via high humidity

Water vapor (relative humidity) is an ineluctable factor for photocatalytic removal of low-concentration NO in practical environment. In this work, defective Bi/BiOBr nanoflowers were synthesized by a solvothermal approach. Benefiting from bismuth and oxygen vacancies, the efficiency of photocatalytic NO removal increased from the initial 26 % to 63 % when exposed to visible light. Furthermore, photocatalytic NO removal performance at various relative humidity levels was explored. It was found that the NO removal efficiency was negligibly affected by humidity. However, the generation of toxic NO2 intermediate was reduced progressively from 87 to 29 ppb as the humidity increased from 5 % to 100 %, which may be attributed to the high hydrophilicity of NO2. The NO-TPD and in-situ DRIFTS were further employed to unveil the pathway of adsorption and photocatalytic removal of NO. This study discloses a strategy for effectively removing NO from the atmosphere by reducing emission of harmful intermediate NO2.