Magnetic NiFe2O4 nanoparticles decorated on N-doped BiOBr nanosheets for expeditious visible light photocatalytic phenol degradation and hexavalent chromium reduction via a Z-scheme heterojunction mechanism

In the present work, new Z-scheme N-BiOBr/NiFe2O4 nanocomposites were successfully constructed by a facile hydrothermal method. Various analytical characterization techniques were employed to examine the physicochemical and optical absorption properties of prepared photocatalysts. The prepared N-BiOBr/NiFe2O4 nanocomposites considerably enhanced the simultaneous visible light removal of phenol and Cr(VI) when compared with single-phase component photocatalysts. Especially, the N-BiOBr/NiFe2O4-15 nanocomposite demonstrated the top-flight photoactivity. The formed Z-scheme system in the nanocomposite significantly decreased the charge carrier recombination and improved the photoactivity. Photoluminescence and photoelectrochemical measurements were conducted to confirm the evidence of efficient charge carrier separation by the nanocomposites. Moreover, the N-BiOBr/NiFe2O4-15 nanocomposite can be magnetically separated and possessed good recycle performance up to five successive runs. The active species capturing experiments demonstrated that the hydroxyl radicals can degrade the phenol efficiently and that photogenerated electrons can reduce the Cr(VI). Finally, the mechanism of excellent photoactivity of N-BiOBr/NiFe2O4 nanocomposite was discussed.