Synthesis, characterization and enhanced visible light photocatalytic activity of Bi2MoO6/Zn–Al layered double hydroxide hierarchical heterostructures

Abstract

Bi₂MoO₆/Zn–Al layered double hydroxide (LDH) hierarchical heterostructures assembled from Bi₂MoO₆ hierarchical hollow spheres and Zn–Al LDH nanosheets were synthesized by a low-temperature hydrothermal method. X-ray diffraction, Fourier transform-infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS) confirmed the formation of the Bi₂MoO₆/Zn–Al LDH composites. Morphologies were characterized by scanning electron microscopy and transmission electron microscopy (TEM). XPS and high resolution TEM indicated the formation of a Bi₂MoO₆/Zn–Al LDH heterojunction. Increasing the LDH content from 0 to 27.0 wt.% caused the Brunauer–Emmett–Teller (BET) specific surface area of the composites to gradually increase. The photocatalytic degradation activity for Rhodamine B (RhB) under visible light irradiation exhibited a large enhancement, followed by a decrease, with increasing LDH content. The Bi₂MoO₆/Zn–Al LDH heterostructure composite with LDH content of 5.5 wt.% showed the highest photocatalytic activity and degraded 99% of RhB in 80 min, while Bi₂MoO₆ degraded less than 50%. The average photocatalytic efficiency is enhanced by more than 100%. The enhanced photocatalytic activity of the Bi₂MoO₆/Zn–Al LDH heterostructure photocatalyst was mainly attributed to the efficient separation of photoinduced electrons and holes. Superoxide radicals and holes were the major active species. The Bi₂MoO₆/Zn–Al LDH heterostructure photocatalyst exhibited excellent stability and reusability. A detailed mechanism for its enhanced photocatalytic activity was discussed in this study. This work provides an effective way to fabricate a series of Bi-based and LDH-containing heterostructure photocatalysts.