Rhodamine B degradation over visible light promoted Bi2WO6/Bi2W0.75Mo0.25O6 and Bi2MoO6/Bi2W0.75Mo0.25O6 heterostructures: DFT and photocatalytic studies

Abstract

In the recent past, the dye degradation through semiconductor photocatalysis under visible light has drawn the widespread attention. In this view, visible active (1-x)Bi₂WO₆/xBi₂W_0.75Mo_0.25O₆ and (1-x)Bi₂MoO₆/xBi₂W_0.75Mo_0.25O₆ (commonly 0.05 ≤ x ≤ 0.20 wt%) heterostructures prepared through a one-step hydrothermal process. These compounds were analyzed by XRD, FE-SEM, HRTEM, XPS, FT-IR, DFT, UV-Vis DRS and photoluminescence. In (1-x)Bi₂WO₆/xBi₂W_0.75Mo_0.25O₆, the 0.90Bi₂WO₆/0.10Bi₂W_0.75Mo_0.25O₆ heterostructure showed the highest photocatalytic activity in comparison with Bi₂WO₆ and Bi₂W_0.75Mo_0.25O₆. On contrary, all (1-x)Bi₂MoO₆/xBi₂W_0.75Mo_0.25O₆ heterostructures exhibited the less photocatalytic activity than that of Bi₂MoO₆. The analysis carried out on both heterostructures clearly demonstrated that (1-x)Bi₂WO₆/xBi₂W_0.75Mo_0.25O₆ is more active in comparison to (1-x)Bi₂MoO₆/xBi₂W_0.75Mo_0.25O_6. The radical trapping test was conducted for 0.90Bi₂WO₆/ 0.10Bi₂W_0.75Mo_0.25O₆ heterostructure, asserted that $O_2^{\bullet -}$ and $h^{+}$radicals were dominant species responsible for Rhodamine B (Rh B) photo-degradation. The estimated redox potentials of Bi₂WO₆, Bi₂W_0.75Mo_0.25O₆ establish the fact that the charge (e^-/h⁺) migration between Bi₂WO₆ and Bi₂W_0.75Mo_0.25O₆ via Z scheme is accountable for the aggressive photocatalytic activity of Bi₂WO₆/Bi₂W_0.75Mo_0.25O₆ heterostructure. The plausible Z scheme mechanism of the generation of electron-hole pairs, charge transfer and also visible light-induced degradation of Rh B was proposed.