Intrinsic facet-dependent electrochemical activities of BiOBr nanosheets for Br- exchange in electrochemically switched ion exchange process

Creating surface atomic arrangement and coordination of BiOBr with a special highly-exposed crystal facet could significantly alter its performance. Although many efforts have been made to explore the relationship between the exposed facet and photo-reactivity, little has been done to investigate Br- exchange activity on the specific facet during an electrochemically switched ion exchange (ESIX) process. In this study, BiOBr nanosheets with highly exposed (001) and (010) facets (named as BOB-001 and BOB-001, respectively) were synthesized, and the effect of exposed crystal facet on ESIX activity was investigated for the first time. The electrochemical investigation suggested that the BOB-010 had better ESIX performance for Br- recovery than the BOB-001. Due to the difference in the surface state as well as the property, the Bi-O bond of the exposed [Bi2O2] layer in the BOB -001 could be broken at a higher potential for the exchange of Br-. While for the BOB-010, Br- could easily pass through the open channel between the [Bi2O2] layers for ion exchange. Furthermore, the photo-assisted elec-trochemically switched ion exchange (P-ESIX) performances of BOB-001 and BOB-010 were investigated. It is found that the real photo-assisted performance of BOB-010 was remarkably higher than that of BOB-001 because of its better photo-response characteristics. This study gives a better insight into the facet-dependent electro-chemical ion-exchange performance of BiOBr.

Automated summary

By creating a special highly-exposed crystal facet, the surface atomic arrangement and coordination of BiOBr can be significantly altered to improve its performance. In this study, the effect of different exposed crystal facets on the electrochemically switched ion exchange (ESIX) activity of BiOBr was investigated. The results showed that the BOB-010 nanosheets had better ESIX performance for Br- recovery compared to BOB-001, primarily due to its better photo-response characteristics and the ease of ion exchange through open channels between [Bi2O2] layers.