Transformation of amorphous Bi2O3 to crystal Bi2O2CO3 on Bi nanospheres surface for photocatalytic NOx oxidation: Intensified hot-electron transfer and reactive oxygen species generation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2021-09, Vol.420, p.129814, Article 129814
• Main Authors: Zhang, Peng, Rao, Yongfang, Huang, Yu, Chen, Meijuan, Huang, Tingting, Ho, Wingkei, Lee, Shuncheng, Zhong, Junbo, Cao, Junji
• Format: Article
• Language: English
• Subjects: Bi@Bi2O2CO3; Crystal transformation; Hot electron transfer; O2− radicals; Photocatalytic oxidation NOx
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2021.129814

[Display omitted] •Amorphous Bi2O3 shell on the surface of Bi nanospheres was transformed to crystal Bi2O2CO3.•Bi2O2CO3 shell reduced the transmission resistance of hot electrons excited from Bi core.•The generation of reactive oxygen species were enhanced over Bi@crystal Bi2O2CO3.••O2− radicals were the major reactive oxidation species contributing to the oxidation of NOx.•Generation mechanisms of ROS were proposed over Bi@crystal Bi2O2CO3 photocatalyst. The inevitable amorphous Bi2O3 on the surface of plasmonic Bi nanospheres serving as the recombination center of hot electron-hole pairs, hindered the transfer of photo-generated hot electrons and production of reactive oxygen species (ROS) seriously. In this study, Bi@amorphous Bi2O3 was transformed to Bi@crystal Bi2O2CO3 by secondary hydrothermal reaction. Bi@Bi2O2CO3 core–shell photocatalyst exhibited higher visible-light catalytic activity (34.1%) than Bi@Bi2O3 did (12.3%) in terms of NOx removal. Photoelectrochemical, surface photovoltage spectroscopy spectra and Kelvin probe force microscopy measurement results indicate that Bi2O2CO3 shell reduced the transmission resistance of hot electrons excited from Bi core. O2-TPD, trapping experiments and density functional theory further confirmed that the transferred hot electrons were a help for ROS generation and •O2− radicals were the major contributor. This study not only addresses the unsettled issue of surface amorphous Bi2O3, but also provides a facile method to transform the amorphous shell to crystal phase of core–shell photocatalyst and new insights into the hot electrons separation and the formation of main ROS over the surface crystal transition of plasmonic Bi.