Fabrication of Novel Z-Scheme Bi₂WO₆/NaBiO₃ Nanocomposites with Enhanced Photocatalytic Activity in the Degradation of 2,3-Dichlorophenol

The Z-scheme Bi₂WO₆/NaBiO₃ nanocomposites were first fabricated by a facile hydrothermal method, and were then characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive spectrometer, Fourier-transform-infrared spectroscopy, X-ray photoelectron spectroscopy and N₂ adsorption–desorption. The as-prepared Bi₂WO₆/NaBiO₃ nanocomposites exhibit outstanding photocatalytic activity and recyclability. A 98.4% photodegradation of 2,3-dichlorophenol (50 mg·L⁻¹) was attained in the presence of Bi₂WO₆/NaBiO₃ (1:10) under the visible-light irradiation in 30 min. In particular, the photocatalytic mechanism has been discussed in detail, based on four aspects: (1) oxidative species, (2) photoelectrochemical performance, (3) conduction band and valence band energy levels and (4) possible transition states and reactions. In conclusion, O⁻ ₂ is the main active oxidative species in the Bi₂WO₆/NaBiO₃ nanocomposite. The material has higher photocurrent and visible light adsorption but lower electron–hole pairs recombination, which contributes to distinguished photocatalytic efficiency. The Z-scheme photocatalytic path was proposed and the possible degradation process and routes have been summarized.