Enhanced photocatalytic reduction of Cr (VI) using porous hierarchical Bi2O3/Bi2S3 high-low heterojunctions: Novel strategies and charge transfer mechanisms

High-low heterojunctions derived from metal-organic frameworks (MOFs) have promising applications in photocatalytic wastewater treatment because of their high photo-redox ability and boosted charge separation efficiency. Herein, Bi-MOF derived porous hierarchical Bi 2 O 3 /Bi 2 S 3 nanoflower-like heterojunctions were prepared by the calcination-hydrothermal method. The optimized Bi 2 O 3 /Bi 2 S 3-2 composite showed a higher degradation rate of Cr (VI) (99.79 % in 30 min) than the pure substance. Moreover, comprehensive studies were conducted on the kinetics, stability and recycling of Bi 2 O 3 /Bi 2 S 3 , as well as optical characteristics. The active species trapping experiments confirmed that e- plays a dominant role in the elimination of Cr (VI). These findings provided novel strategies for construction of porous hierarchical heterojunctions with advanced visible-light-induced degradation performance. The enhanced photo-degradation efficiency of the optimal nanocomposite was assigned to the higher visible-light absorbance, separation of photogenerated carriers, reduced recombination of photo-induced carriers, and enhanced redox capability owing to the construction of porous hierarchical heterojunctions amongst the components.