Facile fabrication of heterostructured bismuth titanate nanocomposites: The effects of composition and band gap structure on the photocatalytic activity performance

Heterostructured Bi2Ti2O7/Bi4Ti3O12 nanocomposites were successfully synthesized through a facile calcination method. The composition and band gap of the Bi2Ti2O7/Bi4Ti3O12 nanocomposites were controlled by tuning the calcination temperature. The morphology of the Bi2Ti2O7/Bi4Ti3O12 composite changed from worm-like nanosheets to spherical particles when the calcination temperature increased from 500 to 800 °C. The structural features of the heterojunction were confirmed using characterization techniques such as XRD, SEM, HRTEM, ESR, and SPV. The Bi2Ti2O7/Bi4Ti3O12 nanocomposite calcined at 600 °C had the highest visible light photocatalytic activity, which was almost 2.0 times as high as that of the pure Bi2Ti2O7 for Rhodamine B (RhB) photodegradation, and 2.5 times the rate of 2,4–dichlorophenol (2,4–DCP) removal under simulated sunlight irradiation. The enhanced photocatalytic activity is due to the heterojunction interfaces induced by the match of lattice and energy levels between Bi2Ti2O7 and Bi4Ti3O12, which is helpful for the separation and transfer of electron-hole pairs. The photocatalytic mechanism was elucidated via active species trapping experiments and electron spin resonance. The photogenerated holes played a key role in the degradation reaction via the Bi2Ti2O7/Bi4Ti3O12 composites. Finally, a possible charge transfer mechanism for the enhanced photocatalytic activity was proposed.