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.