Construction of Bi2O3 quantum Dots/SrBi4Ti4O15 S-scheme heterojunction with enhanced photocatalytic CO2 reduction: Role of Bi2O3 quantum dots and mechanism study

The development of layered structure (Bi2O2)(2+) semiconductors have received extensive concern in energy and environment research attributable to their distinct layered structure, optical and electronic properties. However, the low charge separation efficiency and the tardy electron transfer process are limited the large-scale studies of bismuth-based materials. Herein, Bi2O3 quantum dots/SrBi4Ti4O15 S-scheme heterojunction (SBTO-1) with atomically ultra-thin structure is successfully synthesized through hydrothermal method by using hexadecyl trimethyl ammonium bromide (CTAB) as assistant. As compared with solely SrBi4Ti4O15, electrochemical tests showed that the as-prepared heterojunction greatly shortened the electron diffusion distance inside the photo-catalyst and significantly increased the separation of electron-hole pairs. Meanwhile, the SBTO-1 heterojunction constructed based on Bi2O3 quantum dots can enhance the specific surface area and increase the active sites. Consequently, this S-scheme heterojunction material showed superior photocatalytic performance that CO and CH4 generations reach up to 73.0 and 30.2 mu molg(-1), respectively, which are about 3 and 30 times higher than the pure SrBi4Ti4O15. More importantly, even under the air atmosphere, the SBTO-1 composite still presented excellent photocatalytic CO2 reduction ability. Density functional theory (DFT) calculations and electron para-magnetic resonance (EPR) confirmed that electrons can be transferred to SrBi4Ti4O15 by Bi2O3 after constructing heterojunction, which has excellent charge separation ability. In-situ infrared further explained that the bidentate formate species (COO-and -HCOO-) were a crucial intermediate for photocatalytic CO2 reduction. This study provided some fresh insights for the design of bismuth-based photocatalysts that can capture CO2 signif-icantly and effectively transform CO2.