A facile route to the synthesis of magnetically separable BiOBr/NiFe₂O₄ composites with enhanced photocatalytic performance

Highlights: • Novel magnetically separable BiOBr/NiFe₂O₄ nanocomposite was successfully prepared. • BiOBr/NiFe₂O₄ composite photocatalyst exhibited excellent activity and stability. • An enhanced mechanism of the catalytic activity over the nanocomposite was proposed. - Abstract: Novel magnetically separable BiOBr/NiFe₂O₄ composite photocatalysts with different mass ratios were fabricated through a facile hydrothermal treatment. The phases, morphologies and photophysical properties of the as-obtained samples were characterized by X-ray diffraction (XRD), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microcopy (TEM) and diffuse reflection spectroscopy (DRS). Their visible light photocatalytic performances were examined by degradation of methylene blue (MB) and phenol. Compared with bare BiOBr and NiFe₂O₄, all heterostructured BiOBr/NiFe₂O₄ nanocomposites exhibited significantly enhanced photocatalytic efficiency. The BiOBr/NiFe₂O₄-20% composite showed the highest photodegradation capacity, which was about 3.2 and 22.4 times greater than that of individual BiOBr and NiFe₂O₄, respectively. The degradation efficiency of BiOBr/NiFe₂O₄-20% in the degradation of MB dye hardly changed after five cycles, signifying that the BiOBr/NiFe₂O₄-20% photocatalyst had excellent recyclability. In addition, BiOBr/NiFe₂O₄ composite photocatalysts could be easily separated from contaminant solution by using a magnet and recycled, exhibiting great potential for application in the fields of environmental purification of organic pollutants and wastewater treatment. In the light of experimental results, we proposed a photocatalytic mechanism which confirmed that the enhancement of photocatalytic performance for BiOBr/NiFe₂O₄ composites was mainly ascribed to the efficient separation of photo-induced charges resulting from the well-known "heterostructure effect" between NiFe₂O₄ nanorods and BiOBr nanosheets.