Synergistic effects of crystal structure and oxygen vacancy on Bi₂O₃ polymorphs: intermediates activation,...

This work unraveled the synergistic effects of crystal structure and oxygen vacancy on the photocatalytic activity of Bi₂O₃ polymorphs at an atomic level for the first time. The artificial oxygen vacancy is introduced into α-Bi₂O₃ and β-Bi₂O₃ via a facile method to engineer the band structures and transportation of carriers and redox reaction for highly enhanced photocatalysis. After the optimization, the photocatalytic NO removal ratio on defective β-Bi₂O₃ was increased from 25.2% to 52.0% under visible light irradiation. On defective α-Bi₂O₃, the NO removal ratio is just increased from 7.3% to 20.1%. The difference in the activity enhancement is associated with the different structure of crystal phase and oxygen vacancy. The density functional theory (DFT) calculation and experimental results confirm that the oxygen vacancy in α-Bi₂O₃ and β-Bi₂O₃ could promote the activation of reactants and intermediate as active centers. The crystal structure and oxygen vacancy could synergistically regulate the electrons transfer pathway. On defective β-Bi₂O₃ with tunnel structure, the reactants activation and charge transfer were more efficient than that on α-Bi₂O₃ with zigzag-type configuration because the defect structures on the surface of α-Bi₂O₃ and β-Bi₂O₃ were different. Moreover, the in situ FT-IR revealed the mechanisms of photocatalytic NO oxidation. The photocatalytic NO conversion pathway on α-Bi₂O₃ and β-Bi₂O₃ can be tuned by the different surface defect structures. This work could provide a novel strategy to regulate the photocatalytic activity and conversion pathway via the synergistic effects of crystal structure and oxygen vacancy.