Synergistic effects of crystal structure and oxygen vacancy on Bi2O3 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 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.