Facile Synthesis of Hierarchically Structured Bi₂S₃/Bi₂WO₆ Photocatalysts for Highly Efficient Reduction of Cr(VI)

Abstract

Varied morphologies and compositions of bismuth tungstate nanocomposites have been investigated as promising materials for photocatalytic applications. Among these nanocomposites, hierarchically structured bismuth sulphide (Bi 2 S 3 )/bismuth tungstate (Bi 2 WO 6 ) hybrids have significant photocatalytic efficiency toward heavy metal ions. In order to simplify the synthetic procedure for this desirable composite, we developed a robust single-step hydrothermal synthesis for the formation of hierarchically structured hetero-catalysts of Bi 2 S 3 /Bi 2 WO 6 with a high yield (>95%). The synthesized heterostructures were characterized by various spectroscopic, microscopic, and surface area analysis techniques, which confirmed the successful incorporation of Bi 2 S 3 into the Bi 2 WO 6 matrix and were used to optimize pore size for enhanced catalytic activity. The resulting Bi 2 S 3 /Bi 2 WO 6 heterocatalysts were used to remove toxic Cr(VI) ions via reduction to water insoluble Cr(III) utilizing visible-light irradiation. We also investigated the role of citric acid as a hole scavenger in the reduction of Cr(VI) with minimizing the rate of electron-hole recombination during photocatalysis. Likewise, the observed catalytic activity was significantly enhanced under a condition of an appropriate balance between hierarchical structure of catalysts and the amount of hole scavenger. ASSOCIATED CONTENT Supporting informationAdditional information about FESEM images of Bi 2 WO 6 synthesized under different conditions, comparative XPS of Bi 4f and W 4f, BET surface area and BJH pore size distribution, digital photograph of Cr(VI) reduction to Cr(III) along with effect of CA on Cr(VI) reduction in dark, energy level diagram of composite. This material is available free of charge via internet at

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