Steering photo-excitons towards active sites: Intensified substrates affinity and spatial charge separation for photocatalytic molecular oxygen activation and pollutant removal

Abstract

Bismuth oxybromide-based heterostructure has been constructed widely for various photocatalytic application. However, the function of the exposed facets in heterostructure still remains to be elucidated. Herein, we chemically implanted bismuth oxybromide nano-units with dominantly exposed (010) facets on indium vanadate particles to form composites. Results showed that the absorption range of visible light was extended due to the high photosensitivity of InVO4 and the charge transfer was also effectively expedited by the formation of internal electric field. Contrast experiments manifested that BiOBr with dominant (010) facets was more suitable than that with (001) facets to act as electron acceptor in InVO4/BiOBr heterojunction, because the open channels on (010) facets provided large accommodation space for organic pollutants. Thus, the generated superoxide radicals on BiOBr could annihilate the adsorbed pollutants rapidly. Moreover, the hierarchical core-shell structure provided large surface area to further intensify the affinity of InVO4/BiOBr composites to pollutants. Consequently, the hierarchical InVO4/BiOBr heterojunction exhibited excellent photocatalytic activity and could degrade 92.59% of ciprofloxacin (CIP) within 1 h under visible light. The reaction data were fitted with multiple models to investigate the whole reaction process. Furthermore, the impacts of various simulated actual factors on CIP adsorption and degradation were explored. The intermediates and possible degradation pathways were also illustrated through Liquid Chromatography-Mass/Mass Spectrometry (LC-MS). This work not only provide a facet engineering concept for heterojunction construction, but also help us to further understand the relationship between adsorption and photocatalytic degradation.