Morphology-controlled Synthesis Of Bi₂S₃-based Photocatalysts And Their Photocatalytic Performance

Nano-scaled semiconductors have received increasing interests to serve as photocatalysts in wastewater treatment. In this thesis, morphology-tunable Bi2S3 nanostructures and Bi2S3-TiO2 heterostructures have been synthesized and their morphology-dependent photocatalytic performances have been studied.In Chapter 1, the principle theories of heterogenerous photocatalysis and recent progress of Bi2S3 nanostructures have been reviewed.In Chapter 2, Bi2S3 nanostructures with different dimensionalities have been synthesized and the research of their photocatalytic performance on three different dyes has been carried out. Bi2S3 nanostructures including nanodots, nanorods, and discrete single-crystal nanosheets were synthesized through the thermal decomposition of a single-source precursor Bi(S2CNEt2)3 in amine media. The morphology evolution revealed that the Bi2S3 nanorods and nanosheets were developed through the assembling of metastable nanodots and nanorods, and an attachment-recrystallization growth mechanism was proposed for the formation of nanorods and nanosheets. As for the photocatalysis, the three kinds of nanocrystals could selectively enhance the photodegradation of three typical dyes including rhodamine B, methylene blue, methyl orange, and the efficiencies were dependent on dimensionalities.In order to improve the photocatalytic efficiency of Bi2S3 under visible light irradiation, in Chapter 3, Bi2S3-TiO2 heterostructures were conveniently synthesized by hydrothermal method. Experimental variables had obvious influence on the structure and morphology of the heterostructures. After optimizing the experimental parameters, such as the concentration of Bi precursor, molar ratio of Ti/Bi and the volume of acetone, we determined the most suitable conditions, under which there was a high coverage of TiO2 nanoparticles on Bi2S3 nanorods, and the photocatalytic activities of Bi2S3-TiO2 heterostructures reached the maximum. Through the comparison of photocatalytic activities between Bi2S3-TiO2 heterostructures and P 25, blank TiO2 and Bi2S3, as well as the mechanical mixture of them, we found that there was an interaction between TiO2 and Bi2S3, leading to an improved electron-hole pairs separation and causing the excellent photocatalytic performance.