Microwave hydrothermal synthesis of a Bi2SiO5/Bi12SiO20 heterojunction with oxygen vacancies and multiple charge transfer for enhanced photocatalytic activity

• Published in: Applied surface science 2022-04, Vol.581, p.152337, Article 152337
• Main Authors: Zhang, Qi, Ravindra, Xia, Hongying, Zhang, Libo, Zeng, Kangqing, Xu, Yingjie, Xin, Chunfu
• Format: Article
• Language: English
• Subjects: Bi2SiO5/Bi12SiO20 heterojunction; Microwave hydrothermal; Oxygen vacancy; Photocatalysts
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2021.152337

The traditional heterojunction and Z-Scheme heterojunction system cannot explain the photocatalytic degradation process of the Bi2SiO5/Bi12SiO20 heterojunction. In this paper, we have successfully explained the mechanism by which the heterojunction system generates h+ and O2− radicals in the experiment and proposed the mechanism of multichannel charge transfer by the interaction between the heterojunction and oxygen vacancies. Finally, we proposed that the effect of Bi2SiO5/Bi12SiO20 on the photodegradation of dye is due to the combined action of the heterojunction and oxygen vacancies through multiple charge transfer channels improve the photocatalytic effect. [Display omitted] •I truly hope this highlight could help you:•A novel Bi2SiO5/Bi12SiO20 heterojunction was synthesized by MV hydrothermal method.•Bi2SiO5/Bi12SiO20 exhibited more higher degradation efficiency than Bi12SiO20.•A new photocatalytic mechanism for heterojunction action is proposed and discussed.•The heterojunction photocatalyst has good photocatalytic activity even after 5 cycles. A novel Bi2SiO5/Bi12SiO20 heterojunction photocatalyst was synthesized by microwave hydrothermal synthesis using Bi(NO3)3 and nano-SiO2 as precursors. The as-prepared Bi2SiO5/Bi12SiO20 heterojunction exhibited more efficient charge separation and higher ultraviolet (UV) light photocatalytic activity in the degradation of rhodamine B (Rh-B) and methylene blue (MB). The optimal reaction rate constant of the Bi2SiO5/Bi12SiO20 heterojunction photocatalyst is 3 and 4.3 times higher than that of Bi12SiO20, respectively. Experimental results reveal that the high photocatalytic performance of Bi2SiO5/Bi12SiO20 could be attributed to its larger specific surface area, good crystallinity, smaller particle morphology, and remarkable improvement of charge separation ability via the heterojunctions. The influence of Bi2SiO5/Bi12SiO20 on the charge separation efficiency and optical properties was investigated by electrochemical impedance spectroscopy and photocurrent analysis. Basis on DMPO-ESR spin trapping and radical scavenger experiments, the active species produced from the Bi2SiO5/Bi12SiO20 heterojunction under UV light irradiation were superoxide radicals (O2−) and holes (h+). Additionally, the possible photocatalytic mechanism of the Bi2SiO5/Bi12SiO20 heterojunction was discussed, and finally, a photocatalytic degradation mechanism based on multiple charge transfer channels was proposed. Furthermore, the Bi2SiO5/Bi12