Synergistic effects of crystal structure and oxygen vacancy on BiO polymorphs: intermediates activation, photocatalytic reaction efficiency, and conversion pathway.

This work unraveled the synergistic effects of crystal structure and oxygen vacancy on the photocatalytic activity of BiO polymorphs at an atomic level for the first time. The artificial oxygen vacancy is introduced into α-BiO and β-BiO 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-BiO was increased from 25.2% to 52.0% under visible light irradiation. On defective α-BiO, 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-BiO and β-BiO 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-BiO with tunnel structure, the reactants activation and charge transfer were more efficient than that on α-BiO with zigzag-type configuration because the defect structures on the surface of α-BiO and β-BiO were different. Moreover, the in situ FT-IR revealed the mechanisms of photocatalytic NO oxidation. The photocatalytic NO conversion pathway on α-BiO and β-BiO 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.