Facile synthesis of high crystallinity and oxygen vacancies rich bismuth oxybromide upconversion nanosheets by air-annealing for UV-Vis-NIR broad spectrum driven Bisphenol A degradation

In this paper, we report on a facile solvothermal with a subsequent air-annealing strategy for synthesizing high crystallinity and surface oxygen vacancies (OVs) rich BiOBr:Yb3+/Er3+ upconversion (UC) ultrathin nanosheets, as well as investigating the generation mechanism of OVs. Theoretical calculations and experimental results demonstrate that introducing a suitable concentration of OVs can extend the photoresponse to the NIR region, promote charge carrier separation and enhance the molecular oxygen adsorption and activation. At the same time, NIR light can be converted into Vis light by UC transition of Er3+, enhancing the effective utilization of NIR light. Benefiting from a collaborative promotion effect, the optimized sample (BYE-OV-450) possesses the highest BPA degradation rate, which is 2.60, 5.73, 2.27 and 2.16 times that of BYE-OV-O under UV-Vis-NIR, NIR, Vis, and UV light irradiation, respectively. In addition, the effects of dosages of BYE-OV-450, initial pH, coexisting ions and water matrices on BPA degradation were investigated. This work not only provides an effective and scalable strategy for synthesizing high crystallinity and OVs rich ultrathin bismuth oxyhalides nanosheets, but also presents a new perspective for design and fabrication of full-spectrum responsive highly active photocatalyst for organic pollutant degradation.

Automated summary

This paper presents a facile method for synthesizing BiOBr:Yb3+/Er3+ ultrathin nanosheets with high crystallinity and high surface oxygen vacancies through solvothermal and subsequent air-annealing processes. The introduction of suitable concentrations of oxygen vacancies extends the photoresponse to the NIR region, enhances charge carrier separation, and improves molecular oxygen adsorption. Additionally, the upconversion transition of Er3+ enables the conversion of NIR light to visible light, leading to enhanced utilization of the NIR light.