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The Synthesis Of Bismuth-based Photocatalysts Using Bi2O3 As The Bismuth Source At Low Temperature And Studies Of Their Properties

Posted on:2017-01-29Degree:MasterType:Thesis
Country:ChinaCandidate:J ZhangFull Text:PDF
GTID:2271330488961470Subject:Materials science
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There has been intensive attention in developing semiconductor photocatalytic technology due to its potential applications in solving energy and pollution problems. However, the deficiency of low photon conversion efficiency and narrow band gap for the existing photocatalysts severely hinders their practical application. In addition, the preparation of photocatalysts at low temperature is beneficial to better controlling product microstructure, energy saving and large-scale industrial production because most of the literature have reported that their synthesis were under hydrothermal condition. In this thesis, a series of controllable bismuth-based materials with different morphology have been synthesized via wet chemical methods using Bi2O3 as the bismuth source at low temperature. The photocatalytic activities for pollutant degradation were also discussed. Specific contents are as follows:(1) Well-crystalline bismuth silicon oxide (Bi12SiO20; BSO) samples with a cubic or triangular pyramidal shape were prepared from the reaction of Na2SiO3 and a bismuth oxo compound in alkaline aqueous solution at 70 ℃. All the reactions from different bismuth precursors experienced the same intermediate Bi2O3 to the final product BSO. Given the photocatalytic efficiency of the BSO sample was poor due to the low specific surface area, we successfully overcame the disadvantage of insufficient active sites on the surface of the BSO microcrystallites through etching using HCl/HAc mix solution as the etching agent. The etched BSO crystals with rough surface and uniform egg-tart shaped BiOCl hierarchical microstructures assembled by nanosheets were produced by tuning etchant concentration, which exhibited superior activity for Rhodamine B (RhB) decomposition under visible light.(2) Bismuthyl acetate (CH3COO(BiO); BiOAc) dispersed nanosheets and flower-like hierarchical architectures were easily prepared from the reaction between Bi2O3 and glacial acetic acid (HAc). And the photocatalytic activity of BiOAc samples under UV light was first reported. Especially, BiOAc nanosheets and microflowers could be converted to 8-Bi2O3 by thermal treatment, while the morphology remained unchanged. The as-prepared 5-Bi2O3 exhibited enhanced photocatalytic activity for RhB degradation under simulated sunlight illumination owing to its suitable band gap energy.(3) The nanosheet-based flower-like BiOCl1-xBrx (x= 0-1) hierarchitectures have been prepared by the reaction of Bi2O3 and KCl/KBr in glacial acetic acid solution in dozens of minutes. BiOCl0.5Br0.5 possess highest specific surface area and deep valence band edge position, leading to enhanced photocatalytic performance for RhB degradation than pure BiOCl, BiOBr and other BiOCl1-xBrx(x= 0.25,0.75) samples under visible light irradiation.
Keywords/Search Tags:Bismuth-based compounds, Semiconductor, Adsorption, Photocatalysis
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