Ultra-thin Bi₂WO₆ porous nanosheets with high lattice coherence for enhanced performance for photocatalytic reduction of Cr(VI)

Bi₂WO₆ porous nanosheets (PNS) with different thickness were synthesized via one-pot hydrothermal method. The thickness of Bi₂WO₆ nanosheets could be well controlled from ∼27 nm to ∼16 nm by adjusting the precursor concentration. In addition, the PNS exhibited porous structures, high surface area and high lattice coherence, which increased the number of catalytic sites and facilitated the charge migration within the sheet structure. The Cr(VI) reduction experiments showed that the photocatalytic activity was greatly affected by the thickness of the product and the optimal photocatalytic activity under visible light irradiation was achieved by BWO-3 with thickness of ∼18 nm. The photocatalytic ratio of Cr(VI) reduction for BWO-3 reached to ∼99.5% after 100 min visible light irradiation, which was higher than that of BWO (∼78%). Based on the optical and electrochemical measurements, BWO-3 had upshifted conduction band of 0.05 V, prolonged carriers' lifetime of 2.03 ns and decreased carriers' recombination efficiency compared to BWO. These results endowed BWO-3 with high photoreduction ability, increased transfer and separation efficiency of carriers, and thus enhanced the photoreduction activity.