Facile preparation of BiOX (X = Cl, Br, I) nanoparticles and up-conversion phosphors/BiOBr composites for efficient degradation of NO gas: Oxygen vacancy effect and near infrared light responsive mechanism

With the deterioration of air quality, photocatalysis as a green chemical method has attracted increasing attention. Herein, oxygen vacancies enriched BiOX (X = Cl, Br, I) nanoparticles, which were prepared by a facile precipitation method at room temperature, are employed for photocatalytic removal of toxic NO gas. By introducing glycerol in the reaction solution, more oxygen vacancies are produced in BiOX nanoparticle, finally extending light absorption of the samples to longer-wavelength light. The as-prepared BiOCl and BiOBr nanoparticles presented excellent UV, short and long wavelengths of visible lights (>510 nm) induced photocatalytic NO gas removal activity, which are comparable to those of the popular C-TiO2 and N-TiO2. Furthermore, the up-conversion phosphors were coupled with the representative BiOBr nanoparticles by simple method at room temperature to fulfill UV, visible and NIR lights responsive photocatalysis. Owing to the closely contact, narrowed band gap of BiOBr and nice energy conversion from up-conversion phosphor to BiOBr, the up-conversion phosphors/BiOBr composites not only exhibited excellent UV, short and long wavelengths of visible lights driven photocatalytic activity, but also showed promising NIR light induced one. Under the irradiation of NIR light, the calculated apparent quantum efficiencies of NO removal by B-UP/BiOBr and G-UP/BiOBr composites are about 2.52 and 1.92%, respectively. The up-conversion phosphors coupled BiOBr composites in this work provide potential materials for the high efficiency of UV, visible and NIR lights induced photocatalysis toward air decontamination.