Self-integrated β-Bi2O3/Bi2O2.33@Bi2O2CO3 ternary composites: Formation mechanism and visible light photocatalytic activity

Bi 2 O 2 CO 3 with a narrow band gap ( Eg   ∼   2.93   eV) was self-assembled by Bi 2 O 2 CO 3 nanosheets via a hydrothermal method, and the β-Bi 2 O 3 /Bi 2 O 2.33 @Bi 2 O 2 CO 3 composites were further fabricated using Bi 2 O 2 CO 3 as template by slow thermal decomposition for 4   h, described as: Bi 2 O 2 CO 3   →   β-Bi 2 O 3 /Bi 2 O 2.33 @Bi 2 O 2 CO 3 (300   °C)   →   β-Bi 2 O 3 /Bi 2 O 2.33 (320   °C)   →   β-Bi 2 O 3 (350   °C). Deep investigation towards the generation and existence of β-Bi 2 O 3 and Bi 2 O 2.33 on the surfaces and interfaces of Bi 2 O 2 CO 3 were also carefully conducted by XRD, HRTEM and XPS analysis. In comparison with pure Bi 2 O 2 CO 3 , β-Bi 2 O 3 /Bi 2 O 2.33 @Bi 2 O 2 CO 3 displayed superior photocatalytic degradation efficiency and stability to cationic dyes under visible-light irradiation. Especially, the as-prepared BOC–300   °C with relatively high specific surface area (12.11   m 2   g −1 ) could entirely remove Rh-B and MB in 45   min and 60   min, which were approximately 4.7 and 6.6 times as high as that of pure Bi 2 O 2 CO 3 , respectively. Further study demonstrated that the enhanced photocatalytic degradation efficiency of β-Bi 2 O 3 /Bi 2 O 2.33 @Bi 2 O 2 CO 3 is surely owing to the well matched band gap and p - n heterojunction, which made it possible for much faster charge transfer rather than electron-hole pairs recombination process.