Plasmon Ag and CdS quantum dot co-decorated 3D hierarchical ball-flower-like Bi5O7I nanosheets as tandem heterojunctions for enhanced photothermal–photocatalytic performance

Abstract

Plasmon Ag and CdS quantum dot co-decorated three-dimensional (3D) hierarchical ball-flower-like Bi₅O₇I nanosheets as tandem heterojunction photocatalysts are synthesized by oil bath, photoreduction and hydrothermal processes. The formation of a tandem heterojunction structure facilitates the migration and spatial separation of photogenerated electron–hole pairs. Plasmon Ag nanoparticles can generate hot electrons to enhance the photothermal performance due to the surface plasmon resonance (SPR) effect. The unique 3D hierarchical ball-flower-like Bi₅O₇I nanosheets can provide a number of surface active sites and allow incident light to be reflected multiple times within the Bi₅O₇I nanosheets, thus improving the light utilization. Under the protection of Bi₅O₇I nanosheets, CdS quantum dots which are deposited by a hydrothermal strategy can effectively avoid photocorrosion. In addition, the introduction of Ag nanoparticles and CdS quantum dots extends the photoresponse to the near infrared (NIR) region. The photocatalytic degradation rate of Bi₅O₇I/Ag/CdS composites with a CdS content of 5.76 wt% exhibits the best photocatalytic activity, which is several times higher than that of pristine Bi₅O₇I. The photocatalytic hydrogen evolution is about 10 times higher than that over Bi₅O₇I nanosheets. Moreover, the photothermal efficiency of Bi₅O₇I/Ag/CdS is also improved obviously. The results of cyclic experiments show that the composite photocatalysts have high stability. The outstanding photocatalytic and photothermal performance is attributed to the formation of tandem heterojunctions favoring the separation of charge carriers, the 3D hierarchical structure of Bi₅O₇I offering adequate surface active sites, and the SPR effect of Ag promoting the photothermal effect. These novel Bi₅O₇I/Ag/CdS tandem heterojunctions may provide a new insight into the synthesis of other photocatalysts with synergistic photocatalytic–photothermal effects.