Simultaneous enhancement of charge transfer and light absorption via construction of atom–sharing Bi/Bi3Ti2O8F:Yb3+,Er3+ plasmonic heterojunctions for the efficient degradation of ciprofloxacin

Abstract

The rational design of plasmonic heterojunction photocatalysts is crucial to achieving light capture capability and interfacial charge transfer/separation. Herein, an atom–sharing Bi/Bi3Ti2O8F:Yb3+,Er3+ (Bi/BTOFYE) plasmonic heterojunction with oxygen vacancies and upconversion function was constructed in–situ by self–sacrificing a part of Bi3Ti2O8F:Yb3+,Er3+ (BTOFYE) as source of metallic Bi. The results show that optimum Bi/BTOFYE–2 achieves the highest ciprofloxacin degradation efficiency of 70% within 120 min, with a significant promotion of 1.77 folds compared with BTOFYE. The enhancement mechanism of photocatalysis is not only derived from surface plasmon resonance, oxygen vacancies and upconversion function for the expansion of absorption spectrum and the improvement of carrier separation efficiency. Notably, in–situ interface engineering affords atomic–level close contacts and strong electronic coupling between Bi and BTOFYE, which promote interfacial charge transport and separation, as confirmed experimentally and theoretically. Additionally, the results of cyclic experiments and degradation experiments of different pollutants proved that Bi/BTOFYE was stable and nonselective. The degradation mechanism has been discussed based on the analysis of intermediates of degradation products via liquid chromatography–mass spectrometry. This study provides an idea on how to enhance photocatalysis efficiency by surface plasmon resonance of non–noble metals and makes a case for the development and design of novel atom–level contact heterojunctions.