Synthesis and enhanced visible light photocatalytic activity of WO3-BiOClxBr1−x heterojunctions with tunable energy band structure

A series of WO3-BiOClxBr1−x heterojunctions with tunable energy band structure were successfully synthesized via a hydrothermal method. The photocatalytic activities and reaction mechanism of WO3-BiOClxBr1−x composites were investigated by decomposition of Rhodamine B (RhB). The light absorption ability, energy band structure and photocatalytic activity in WO3-BiOClxBr1−x heterojunctions could be adjusted by changing the mole ratio of Br and Cl. The results revealed that the WO3-BiOClxBr1−x composites exhibited the highest photocatalytic activities than pure WO3 and BiOClxBr1−x under visible light irradiation. The photocatalytic property of WO3-BiOCl can be strengthened mainly owing to the enhanced light absorption ability, while the photocatalytic activities of WO3-BiOClxBr1−x (x = 0, 0.25, 0.5 and 0.75) composites could be enhanced by restricting the recombination of photo-generated electrons and holes. Among them, 5% WO3-BiOCl0.25Br0.75 heterojunction shows the highest photocatalytic activity with RhB completely decomposed in 6 min, this can be contributed to the synergetic effects of energy band structure and light absorption ability. Moreover, the holes and superoxide radical anions were considered as the active species during photocatalytic oxidation process, and the possible mechanism of the enhancement of the photocatalytic property was proposed.