Modulating Adsorption–Redox Sites and Charge Separation of Cs<sub>3</sub>Bi<sub>2</sub>Br<sub>9–<i>x</i></sub>@AgBr Core–Shell Heterostructure for Selective Toluene Photooxidation
Biao Zhou, Kezhou Fan, Yanan Chong, Shuang Xu, Jianwu Wei, Jiake Wei, Aleksandr A. Sergeev, Kam Sing Wong, Tan Li, Guangxu Chen, Daiqi Ye, Keyou Yan
Abstract
Constructing vacancy-decorated heterojunction photocatalysts is a feasible strategy for highly efficient photooxidation of toluene to benzaldehyde. However, poor interface interaction and vacancy-triggered mismatched redox kinetics seriously impede photocatalytic activity improvement. Herein, a chemically bonded Cs 3 Bi 2 Br 9– x @AgBr core–shell heterojunction with unified adsorption-redox sites is fabricated via an in-situ light-assisted Ag + insertion method. Experiments and theoretical calculations demonstrate that the type-II band alignment with interfacial Bi–Br–Ag bonds boosts the charge separation. Moreover, because of the greater oxygen adsorption energy and the steric-hindrance effect of the AgBr shell, the preferred adsorption site of O 2 is modulated from Br vacancy (V Br, trapping holes) to its corresponding reduction site (AgBr, gathering electrons), thereby ensuring V Br -enhancing toluene adsorption/oxidation on Cs 3 Bi 2 Br 9 . Therefore, Cs 3 Bi 2 Br 9– x @AgBr exhibits an improved benzaldehyde production rate of 5.61 mmol g –1 h –1 (selectivity: 91%), outperforming pure Cs 3 Bi 2 Br 9 by a factor of 6. This work underlines the importance of the rational design of vacancy-decorated heterointerface and redox sites at the atomic level in photocatalysis.