Probing the light harvesting and charge rectification of bismuth nanoparticles behind the promoted photoreactivity onto Bi/BiOCl catalyst by (in-situ) electron microscopy

- The enhanced photoactivity on Bi/BiOCl catalyst was studied.
- Bi/BiOCl photocatalyst was prepared in TEM in situ.
- The LSPR absorption of Bi NPs was confirmed by Mono-STEM-EELS and simulation.
- The direct Eg value of single Bi nanoparticle was determined by Mono-STEM-EELS.
- The possible charge transfer between Bi and BiOCl was investigated.

State-of-the-art electron microscopy has enabled us to investigate microstructural details down to sub-subÃ¥ngström and milli-electron-volt resolution level. The enhanced photoreactivity over bismuth hybridized BiOCl catalyst (Bi/BiOCl) has been reported recently, however, the mechanistic understandings of this improved photoreactivity especially the optical behavior of bismuth nanoparticles (Bi NPs) are still obscured and in debate. The optical absorption features of Bi NPs and the charge transfer characteristic between bismuth and BiOCl have been considered as the major physicochemical origin for the promoted photoreactivity. Based on the advanced (in-situ) electron microscopy of monochromated electron energy loss spectroscopy in scanning transmission electron microscopy imaging mode (Mono-STEM-EELS) along with related theoretical investigations, in this work, we for the first time distinguished and explained the optical absorption originated from the localized surface plasmon resonances (LSPR) effect and direct band gap transition in an individual bismuth nanoparticle as well as transportation of photogenerated carriers at the interface of Bi/BiOCl. These findings could provide better understandings about the origin of the improved photoreactivity of various bismuth-hybridized photocatalysts.

The optical absorption of a single bismuth nanoparticle caused by the LSPR effect and direct band gap transition has been distinguished by means of Mono-STEM-EELS technique.138