Maximizing the synergistic effect on accelerated photoelectron transfer of TiO2 by double Z-scheme heterojunctions and specific oxygen vacancies

Photocatalysis is an ideal technology for environmental applications, but its efficiency is severely limited by slow kinetics and low efficiency of carrier separation. Herein, a photocatalyst (TiO2-Bi2Ti2O7-600 degrees C) with homotypic growth possessing double Z-scheme heterojunctions was successfully synthesized by the growth of mixed crystalline phase TiO2 on the surface of Bi2Ti2O7. The carrier separation efficiency of the heterojunctions was enhanced by the photo-ferroelectricity of Bi2Ti2O7. Simultaneously, the interface-fused TiO2/Bi2Ti2O7 provided stability for carrier transport between heterojunctions. Modern instru-mental characterization confirmed that oxygen vacancies mainly exist in Bi-O structural units provided by Bi2Ti2O7 and that the carrier separation efficiency of the double Z-scheme heterojunctions was signifi-cantly higher than that of the single Z-scheme heterojunctions. Density-of-states calculations based on the first principle confirmed that the carrier separation efficiency was higher when the oxygen vacancies presented in the Bi-O structural units than they presented in the Ti-O structural units. TiO2-Bi2Ti2O7- 60 0 degrees C could accomplish the complete degradation of Rh-B (10 mg/L) in aqueous environment within 80 min, instead of only contributing to the destruction of conjugated chromogenic groups in Rh-B. This photocatalyst with stable structure, multiple carrier transport channels, and sufficient oxygen vacancies enables the photoelectrons to concentrate on the confinement effect, opening a novel avenue for the design strategy of new-generation photocatalysts in environmental wastewater applications.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In this study, a photocatalyst (TiO2-Bi2Ti2O7-600℃) with double Z-scheme heterojunctions was successfully synthesized by growing mixed crystalline phase TiO2 on the surface of Bi2Ti2O7. The photo-ferroelectricity of Bi2Ti2O7 enhanced the carrier separation efficiency of the heterojunctions, while the interface-fused TiO2/Bi2Ti2O7 provided stability for carrier transport. Oxygen vacancies mainly existed in Bi-O structural units provided by Bi2Ti2O7, and the carrier separation efficiency of the double Z-scheme heterojunctions was significantly higher than that of the single Z-scheme heterojunctions. TiO2-Bi2Ti2O7-600℃ showed complete degradation of Rh-B (10 mg/L) in aqueous environment within 80 min, opening a new avenue for the design of new-generation photocatalysts in environmental wastewater applications.