Halogen-induced polymorphic Bi2WO6-xhalogen2x with highly photocatalytic performance and mechanism investigation

Element doping is an effective technique to modulate bandgap and improve activity of catalysts. The halogen elements (F, Cl, Br and I) doped Bi2WO6 (F-BWO, Cl-BWO, Br-BWO and I-BWO) were successfully prepared through a simple one-step microwave-assisted solvothermal strategy. The effects of F, Cl, Br and I doping on the crystal structure, morphology, photoelectric and physicochemical properties of the as-prepared samples have been investigated by XRD, SEM, FT-IR, XPS, BET, DRS, PL, EIS, and Tafel. The photocatalytic activity of all the doped samples were improved to varying degrees. Among them, the I-BWO showed the best photocatalytic hydrogen (H2) production (82.53 μmol g-1h−1) and rhodamine B (RhB) photodegradation (99%, 40 min) activities. According to the DFT (density functional theory) calculation, the bandgap regulation effect of halogen on the as-fabricated samples has been confirmed, and the photocatalytic mechanism of the doped catalysts has been discussed. This work systematically discussed the morphology-inducting effect of halogen on Bi2WO6, providing a one-step strategy for designing highly active photocatalysts.