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 BiOCI/Bi2O3 (black BiOCI-Bi-Bi2O3/rGO) heterojunctions with oxygen vacancies were prepared via in situ Fe reduction of BiOCI/graphene oxide nanoplates. In comparison with BiOCI/graphene oxide nanoplates, the black BiOCI-Bi-Bi2O3/rGO heterojunctions have stronger visible-light absorption, and exhibit more efficient charge separation and higher visible-light photo catalytic activity in degrading 2-nitrophenol (2NP). The black BiOCI-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 BiOCI and Bi2O3, multiple charge transfer channels via Bi-bridge and rGO, and efficient charge separation. Of special importance, black BiOCI-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 BiOCI-Bi-Bi2O3/rGO heterojunctions based on multiple charge transfer channels was proposed.