Visible-light-responsive graphene-functionalized Bi-bridge Z-scheme black BiOCl/Bi₂O₃ heterojunction with oxygen vacancy and multiple charge transfer channels for efficient photocatalytic degradation of 2-nitrophenol and industrial wastewater treatment

Although Bi-based compounds are effective photocatalysts for degrading organic pollutants under visible-light irradiation, their visible-light photocatalytic activities are still low and far from practical application. In this study, novel graphene-functionalized Bi-bridge Z-scheme black BiOCl/Bi₂O₃ (black BiOCl-Bi-Bi₂O₃/rGO) heterojunctions with oxygen vacancies were prepared via in situ Fe reduction of BiOCl/graphene oxide nanoplates. In comparison with BiOCl/graphene oxide nanoplates, the black BiOCl-Bi-Bi₂O₃/rGO heterojunctions have stronger visible-light absorption, and exhibit more efficient charge separation and higher visible-light photocatalytic activity in degrading 2-nitrophenol (2NP). The black BiOCl-Bi-Bi₂O₃/rGO_0.4 shows the highest visible-light photocatalytic activity with almost complete degradation of 2NP, which is attributed to proper bandgap match between black BiOCl and Bi₂O₃, multiple charge transfer channels via Bi-bridge and rGO, and efficient charge separation. Of special importance, black BiOCl-Bi-Bi₂O₃/rGO heterojunction can effectively treat real industrial wastewater with 70.3% COD removal efficiency, and it shows superior long-term stability. Additionally, a possible photocatalytic mechanism of black BiOCl-Bi-Bi₂O₃/rGO heterojunctions based on multiple charge transfer channels was proposed.