The Morphology Modulation, Noble Metal Deposition And Photocatalytic Activity Of BiOI

In recent years, semiconductor photocatalysis has obtained extensiveattention in the environmental pollution treatment. BiOI, as the new photocatalyst,has been considered as one of the most potential objects due to its special layeredstructure and remarkable photocatalytic activity. However, the narrow band-gap ofBiOI (~1.75eV) would result in the high recombination rate of photogeneratedcarriers, which greatly reduces the photocatalytic efficiency. Therefore, the purposeof this thesis is the fabrication of the highly active BiOI through morphologymodulation and deposition of noble metal. Moreover, systematic characterizationswere utilized to analyze the enhanced mechanism of its photocatalytic performance.The main research contents of this thesis are presented as follows:(1) A series of plate-like BiOI with different sizes were synthesized by roomtemperature direct hydrolysis method. The sizes and dispersity of BiOI sheetsdepended on the synergetic effects of the volume and concentration of KI solution.The X-ray powder diffraction (XRD) patterns show that all BiOI samples were oftetragonal phase with good crystallinity. Photocatalytic degradation of methyl orange(MO) was carried out to evaluate the activities of BiOI samples under visible light(λ>400nm). BiOI sample prepared under the condition of0.035mol/L KI solutionexhibited the highest photocatalytic activity, corresponding to the92.6%degradationof MO. It is a facile way to obtain plate-like BiOI visible light photocatalyst for theremoval of organic contaminants in waste water.(2) Hierarchical bismuth oxyiodide (BiOI) microflower photocatalysts weresynthesized by hydrolysis at room temperature. The concentration of ethylene glycolwas the major factor that modulated the resulting BiOI morphology. The morphology,elemental composition, crystal phase structure, and absorption properties of the BiOIsamples were characterized. Under visible light irradiation (λ>400nm), BiOI (S10)with microflower morphology exhibited the highest photocatalytic activity in thedegradation of methyl orange. The corresponding apparent pseudo-first-order rateconstant was0.826h-1. The trend in photocatalytic activities of the BiOI samples was coincided with the trend in their photocurrents. This is a useful reference forpreparing hierarchical BiOI microflowers with good visible light-inducedphotocatalytic activity.(3) Using typical BiOI2D plate and3D flower as substrates, two series ofmorphology-dependent Ag/BiOI composites were successfully synthesized by usinga facile photodeposition method. The morphology effects of BiOI on the growth ofAg quantum dots and the photocatalytic activity of Ag/BiOI were discussed. Duringthe photodeposition process, weak separation efficiency of BiOI2D plate facilitatedthe formation of larger sized Ag quantum dots which displayed higher electrontrapping efficiency and resulted in higher photocatalytic activity than those withsmaller size on BiOI3D flower. The pseudo-first-order rate constants kappof BiOIplate and BiOI flower were0.32and0.85h-1, while the corresponding activities ofAg/BiOI were further increased to3.25and1.11times for degrading methyl orange.Similarly, the activities of Ag/BiOI were increased to1.31and1.13times in theprocess of degrading phenol. It is a promising way to regulate the activity of Ag/BiOIeven the universal noble metal/semiconductor composite through controlling themorphology of semiconductor substrate.