In-situ transformation of Bi₂WO₆ to highly photoreactive Bi₂WO₆@Bi₂S₃ nanoplate via ion exchange

As a two dimensional (2D) visible-light-responsive semiconductor photocatalyst, the photoreactivity of Bi₂WO₆ is not high enough for practical application owing to its limited response to visible light and rapid recombination of photogenerated electron-hole pairs. In this paper, 2D core-shell structured Bi₂WO₆@Bi₂S₃ nanoplates were prepared by calcination of a mixture of Bi₂WO₆ (1.3 g) and a certain amount of Na₂S·9H₂O (0–3.0 g) at 350 °C for 2 h. The reactivity of the resulting photocatalyst materials was evaluated by photocatalytic degradation of Brilliant Red X-3B (X3B), an anionic dye, under visible light irradiation (λ > 420 nm). As the amount of Na₂S·9H₂O was increased from 0 to 1.5 g, the degradation rate constant of X3B sharply increased from 0.40 × 10⁻³ to 6.6 × 10⁻³ min⁻¹. The enhanced photocatalytic activity of Bi₂WO₆@Bi₂S₃ was attributed to the photosensitization of Bi₂S₃, which greatly extended the light-responsive range from the visible to the NIR, and the formation of a heterojunction, which retarded the recombination rate of photogenerated electron-hole pairs. However, further increases in the amount of Na₂S·9H₂O (from 1.5 to 3.0 g) resulted in a decrease of the photocatalytic activity of the Bi₂WO₆@Bi₂S₃ nanoplates owing to the formation of a photo-inactive NaBiS₂ layer covering the Bi₂WO₆ surface. Copyright © 2018 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.