Synthesis And Photocatalytic Performance Of Semiconductor-based Hybrid Materials

The photocatalytic oxidation,as a catalytic oxidation technology,has important application feature in the field of environment,pretreatment before analysis of sample,and energy and so on.The photocatalytic oxidation is becoming the research focus on pollution control technology.TiO₂ and metal-organic frameworks have attracted much attention by scientific researchers,owing to their special physical and chemical properties.Therefore,we designed and prepared semiconductor hybrid materials based TiO₂ and metal-organic frameworks for the studies of photocatalysis.This thesis contains following three main parts:（1）Fe₃O₄@SiO₂@TiO₂ composite particles were prepared by the deposition of TiO₂ to the surface of magnetic Fe₃O₄@SiO₂ cores using a sol-gel technique.Subsequently,the Fe₃O₄@SiO₂@TiO₂ composite particles were surfacially modified by salicylic acid with chemical absorption method.In the meantime,the prepared Fe₃O₄@SiO₂@TiO₂ composite particles and Fe₃O₄@SiO₂@TiO₂-coated salicylic acid composite photocatalytic nanomaterials were characterized by means of Fourier transform infrared spectroscopy（FT-IR）,Transmission electron microcopy（TEM）,X-ray diffraction（XRD）.The effects of stirring speed on catalytic activity and magnetic properties of Fe₃O₄@SiO₂@TiO₂ nanoparticles are discussed.The magnetic properties of the composite photocatalysts and its degradation ability for methyl blue are studied,and the effect of degradation time on catalytic activity is discussed.The results indicate that the composite magnetic photocatalyst have high photocatalytic activity for methyl blue and can be re-used by using a magnetic separation regeneration method.（2）Nano-titanium dioxide is widely used as a photocatalyst due to high activity and good stability.Therefore,we fabricated the TiO₂-quantum dot hybrid nanomaterials,i.e.mesoporous TiO₂ was first prepared at 100 ^oC through the hydrothermal method,and then was modified using salicylic acid and nitrogen doped carbon quantum dots in order to produce different functional groups on the surface of mesoporous TiO₂.The best efficency for methylene blue（MB）degradation was reached over mesoporous TiO₂ anatase type modified by salicylic acid and nitrogen doped carbon quantum dots.The MB degradation rate is 98.80%,which was 1.5 times that of pure mesoporous TiO₂.In addition,Fe₃O₄@SiO₂@TiO₂-CdSe@ZnS nanomaterials were prepared successfully,which shows better photocatalytic performance in the the range of visible light.（3）The reduced graphene oxide（rGO）/NH₂-MIL-125（Ti）（rGO-NMTi）hybrid nanocomposite photocatalysts were prepared by a simple and facile solvothermal method and were characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,N₂ adsorption–desorption isotherm,ultraviolet-visible absorption spectra（UV-DRS）and fourier transform infrared spectroscopy（FT-IR）techniques.The results indicated that the rGO/NH₂-MIL-125（Ti）had large surface area and thermal stability,which enhanced greatly visible-light absorption.Compared with pure NH₂-MIL-125（Ti）（MOFs）,the rGO/NH₂-MIL-125（Ti）exhibited more efficiently photocatalytic performance for MB degradation under visible-light irradiation.The optimal rGO content in rGO/NH₂-MIL-125（Ti）is 15 wt%and the corresponding to the efficiency of photo-degradation for MB was 98.6%.Therefore,the rGO/MOFs photocatalysts have great potential on the control of environmental pollution.