The Synthesis And Photocatalytic Performance Of The BiOBr/Cds Or Bi₂S₃ Heterostructures

It is well known that Bi OBr has drawn tremendous attention owing to its high chemical stabilities and excellent visible light photocatalytic activities. The photocatalytic activity of Bi OBr can be further improved by modulating its micro/nanostructure during the growth process. However, the wider band gap(~ 2.90 e V) of Bi OBr severely restricts its practical application under visible light. In this paper, heterostructured Bi OBr/Cd S or Bi2S3 nanocomposites have been successfully synthesized by a facile and effective hydrothermal/solvothermal method. Such hybrid photocatalysts integrate the synergistic effects of the individual species, which could endow the composite systems with increased light harvesting, prolonged lifetime of carriers, enhanced catalytic performance as well as higher chemical stability. The main contents were shown as the followings:⑴ Cd S spheres were synthesized through a samble hydrothermal/solvothermal method. The impact of solvent and the molar ratio of Cd(AC)2?2H2O : CS(NH2)2 on the the morphologies of Cd S and the photocatalytic activity were also discussed. As a result, the Cd S, through the hydrothermal with Cd(AC)2?2H2O : CS(NH2)2 = 1 : 4, exhiits better photocatalytic activity and has a neat and uniform morphology.⑵ Bi2S3 with various morphologies has been successfully synthesized via a solvothermal approach, which is characterized by XRD and FESEM. The photocatalytic activities were evaluated by the decomposition of rhodamine-B(Rh B) under visible light irradiation. However, the Bi2S3 samples exhibit poor photocatalytic performance. Based on the unique physical and chemical properties of Bi2S3, we will further modify Bi2S3 to improve the photocatalytic activity in the latter experiments.⑶ A novel p-n junction BiOBr/CdS composite has been successfully synthesized through a facile two-step method. The p-Bi OBr/n-Cd S composite exhibits significantly enhanced photoelectrochemical current response and photocatalytic performance for decomposing organic dye rhodamine-B(Rh B) compared with pure Bi OBr and Cd S under visible light irradiation(λ > 420 nm), which could be mainly attributed to the formation of p-n heterojunction. The heterojunctioncould provide a potential driving force owing to the building of an internal electric field, with its field direction from the n-type to the p-type semiconductor. As a result, the probability of recombination of photogenerated charge carriers is largely reduced. Additionally, the enlarged specic surface area could play a signicant role for the enhanced photocatalyticactivity. Moreover, photocatalytic mechanism investigations demonstrate that h+ and ?O2- play a key role in p-Bi OBr/n-Cd S hybrid under visible-light irradiation.⑷ We have developed a simple solvothermal approach to fabricate ideal Bi2S3/Bi OBr heterostructures. The as-prepared Bi2S3/Bi OBr exhibits higher photocatalytic activities on the degradation of Rh B or BP than pure Bi OBr under visible light irradiation(λ > 420 nm) due to the formation of Bi2S3-Bi OBr heterojunction which could suppress the recombination of photogenerated electron–hole pairs efficiently. The photocatalytic mechanism demonstrates that the photocatalytic degradation of Rh B or BP could be attributed to the action of h+ via direct hole oxidation process and the oxidation action of the generated ?O2- radicals, but ?OH is verified to be inappreciable in the Bi2S3/Bi OBr photocatalysis.