Use of m-BiVO₄/ZnFe₂O₄ composite materials for enhanced photocatalytic properties

Using sol–gel auto-combustion combined with calcination, spinel zinc ferrite (ZnFe₂O₄) and monoclinic bismuth vanadate (m-BiVO₄) nanopowder were synthesised. On this basis, novel heterojunction-structure monoclinic bismuth vanadate/spinel ferrite ZnFe₂O₄ (BZF) composites were prepared, for the first time, using sol–gel combined with in situ loading. The characteristics of as-prepared materials were ascertained by X-ray diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy. As-prepared pure ZnFe₂O₄ particles were short, rodlike and about 100–200 nm. Pure m-BiVO₄ powder was spindle-like, distributed uniformly and about 150–250 nm. BZF composites were used to degrade methylene orange (MO) under visible-light irradiation. Among as-prepared BZF composites, BZF-15 wt% had optimal photocatalytic activity for degrading MO. The photocatalytic mechanism of the composites was attributed to the effective separation between photo-generated electrons and holes based on the heterojunction energy-band theory.