Polyols-mediated Synthesis Of Bismuth-contained Nanocomposites And Their Enhancement Mechanism For Photocatalysis

Exploring highly efficient photocatalytic systems and studying the enhancement of catalytic activity,as a bridge to realize photocatalysis from laboratoryto practically industrial utilization,are important for dealing with the current environment pollution and energy crisis.Based on the general process of semiconductor photocatalysis,thisthesis designed and synthesized bismuth-contained semiconductor with complexed structuresvia polyols mediated methods.Combined with powder X-ray diffraction?XRD?,scanning electron microscopy?SEM?,X-ray photoelectron spectrum?XPS?,UV-vis diffuse reflectance spectroscopy?DRS?and nitrogen sorption and desorption test,the composition,morphology,optical and physical adsorption property are defined.By employing doping,compositing and surface defects configuration,the following works are conducted to exploring strategies for highly efficient photocatalyst developments and photocatalytic process for degradation of organic wasted compounds.1.Cl incorporated BiOI products with different Cl/I molar ratio have been successfully fabricated via facile fast room temperature method using water and EG as solvent.Photocatalytic activities of the incorporated products were evaluated by degradation of methyl blue,an organic dye for which pure BiOI shows negligible degradation efficiency.Enhanced photocatalytic activity was observed in all incorporated products.Combined photo-electrochemistry characterization and DFT calculation,the enhancement of photocatalytic activities are ascribing to the incorporated Cl ions in the lattice of BiOI,which are found mainly occupied on I sites,inducing a hybrid valance band consisted of I 5p,O 2p and Cl 3p orbitals,results deepen valence band location of the materials.The enhancement of photocatalytic activities are also ascribing that the incorporated Cl ions into the lattice also change the evolution of photogenerated electrons and holes,inducing broadening of bandgap but efficient production of photogenerated carriers.2.Fe doped BiOCl photocatalysts are successfully prepared via a facile one-step room temperature method.XRD,XPS and EDS data of the as-prepared products reveals that the doped Fe ions mainly locates in buck of the material and occupies on Bi sites in the lattice.Photocatalytic activities of the as-prepared products are evaluated by degradation of methyl blue in the absence and in the presence of H₂O₂ under simulated light irradiation,where strongly enhanced degradation are only observed in the presence of H₂O₂ for Fe doped BiOCl,which undergoes a photo-Fenton process and involves a hydroxyl radicals dominated process.The enhanced photo-Fenton activity of the Fe doped products BiOCl compared to the un-doped one is ascribe to the presence of Fe ions in the lattice,which not only extend the solar energy response of the material from 350 nm to 600 nm by creating a new energy level in the forbidden band of BiOCl,but also alter the chemical state of the surface,which induced electron flowing favorably to H₂O₂ rather than oxygen molecular in aqueous solution.3.Bi/BiPO₄ nanocomposites with rich oxygen vacancies are successfully synthesized viaa one-step solvothermal treatment using ethylene glycol?EG?as solvent by simply controlling the reaction times.Enhancement of photocatalytic activity of the nanocomposites was observed for the methyl blue photo-degradation.By detecting the produced reactive intermediates using electron spin resonance?ESR?spectrum,the presence of Bi and oxygen vacancies were found to be benefit for the production of ·OH and ·O₂^-,respectively.DFT calculations showed that the presence of oxygen and Bi in/on the surface of BiPO₄ promoted electron and holes separating efficiently.And as results,Bi and oxygen vacancies as active sites for production of ·OH and ·O₂^-,respectively.