Synthesize, construction and enhanced performance of Bi2WO6/ZnS heterojunction under visible light: Experimental and DFT study

With the simple perovskite structure, Bi2WO6 could be utilized as a modifier to overcome the low visible light response of the wide energy band photocatalyst ZnS. Flower-like Bi2WO6 was simply synthesized by hydrothermal method and Bi2WO6/ZnS heterojunction was constructed via solvothermal reaction. The results showed that ZnS nanospheres were uniformly loaded on the flower-like structure, which was well kept under low concentration loading (≤20%ωt ZnS). The degradation of MB and Rh.B under visible light was used to measure the photocatalytic activity of the photocatalysts. The degradation rates of MB and Rh.B by 20%ωt-Bi2WO6/ZnS were as high as 94.3% and 92.8%, respectively. Moreover, the degradation performance of photocatalyst still maintained 89.3% after 4 times recycling tests. The visible light absorption ability of modified ZnS was improved, and the recombination of photogenerated electrons and holes was inhibited due to the formation of heterojunction. According to the data from density functional theory calculation, the composition of the valence band and conductive band of the Bi2WO6/ZnS system has been altered. The band gap of Bi2WO6/ZnS was reduced by roughly 1.12 eV compared to that of pure ZnS, and the work function analysis were in good agreement with the experimental results. Under light stimulation, electrons were transferred from Bi2WO6 to ZnS to produce superoxide radicals which played key roles in the degradation reaction of dyes.