Novel BiVO4/ZnO heterojunction for amended photoreduction of mercury (II) ions

Abstract

In this research, mercury (II) ions were eliminated via photocatalytic reduction under visible light utilizing BiVO4/ZnO heterojunction. Different percentages of BiVO4 NPs were distributed uniformly over mesoporous ZnO surface. It has been demonstrated by TEM analysis that both pure mesoporous ZnO sample and the heterojunction containing 3 wt% BiVO4 NPs consist of almost homogenous spherical particles of about 25 nm diameter. The progressed BiVO4/ZnO nanocomposite containing 3 wt% BiVO4 NPs was able to accomplish comprehensive elimination of mercury (II) ions via photocatalytic reduction under visible light owing to its significant capacity to absorb light in visible region. Such heterostructure achieved almost complete (100%) photocatalytic proficiency towards mercury (II) ions reduction by the end of 45 min from the illumination by visible light. The photo-reduction rate of Hg2+ ions via practicing BiVO4/ZnO nanocomposite containing 3 wt% BiVO4 NPs was estimated at 14 times when related to that of pure mesoporous ZnO. The successful development of p-n heterojunction between ZnO (n-type) and BiVO4 (p-type) in addition to the accessible great surface area and the remarkable visible light absorption provided by such heterojunction could be regarded as the dominant causes of the distinct photo-reduction rate of Hg2+ ions. The heterojunction afforded via incorporating BiVO4 with ZnO facilitated the separation between the created charges and hindered the rate of the recombination between such charges as well.