Sonochemical synthesis of nanocrystallite Bi2O3 as a visible-light-driven photocatalyst

The synthesis of Bi2O3 by a simple sonochemical route is investigated. Surfactant polyvinylpyrrolidone (PVP) has strong effects on the grain sizes and morphologies of Bi2O3. Bi2O3 single crystallite with grain size of 40–100 nm is obtained in the presence of 0.5 g PVP. X-ray diffraction (XRD) pattern shows that the nanocrystallite Bi2O3 is monoclinic and has a high degree of crystallinity. Optical characterizations show that the nanocrystallite Bi2O3 presents the photoabsorption properties from UV light region to visible light shorter than 470 nm and the band gap of the nanocrystallite Bi2O3 is 2.85 eV. The photocatalytic performance of the nanocrystallite Bi2O3 is evaluated using methyl orange (MeO) as a model pollutant. The photocatalytic results show that such nanocrystallite Bi2O3 can effectively degrade 86% MeO within 100 min under visible light illumination (λ > 400 nm). The action spectrum of MeO degradation over nanocrystallite Bi2O3 further confirms that the photocatalytic reaction can be driven by visible light. The photocatalytic mechanism is also studied based on electronic structure calculations using density functional theory (DFT).