| In recent years,persistent organic pollutants have been detected in surface water,groundwater and even drinking water,which have had a serious impact on human health and living conditions.Thus,over the past few decades,photodegradation of persistent organic pollutants has received increasing attention.Because of its stable physical and chemical properties,high efficiency and low cost,TiO2 gradually acts as the most popular photocatalyst.However,TiO2 is limited by its own bandgap width of 3.20 eV,which can only absorb about 5%of the energy of the sun's ultraviolet light.Various modifications have been made to TiO2,such as metal doping,nonmetallic doping,surface organic modification,and increased adsorption capacity.Although these methods have a certain degree of modification to TiO2,but some methods are complicated,costly and it is difficult to directly apply to industrial manufacturing.Based on the investigation and analysis previous work,in this thesis.carbon-doped anatase phase TiO2 nanoparticles with visible-light response,narrow band gap and black color have been obtained by using a simple and economical experimental method of high-temperature calcination under high-purity nitrogen(N2).And the carbon-doped samples viwith different widths of band gap are obtained by the calcinations at different temperatures.Besides,according to the ligand-to-metal charge transfer(LMCT)effect,we also have prepared complex TiO2 nanoparticles with surface complex formed by benzemethanol molecules,and benzyl alcohol modified TiO2 nanoparticles.We have systematically studied visible-light response properties of the samples of carbon-doped TiO2,complex TiO2,and BnOH modified TiO2,including light absorption properties,adsorption properties,photocatalytic activity and so on.In addition,an all-solid-state TiO2 solar cell has been prepared by relying on the carbon doping materials.The main contents and innovation points are summarized as below.1.Lltrafine TiO2 nanoparticles have been synthesized by sol method and black anatase phase TiO2 nanoparticles with visible light absorption have been obtained by further calcining the ultrafine TiO2 nanoparticles under high-purity nitrogen gas at different calcination temperatures.The bandgaps optically obtained in such a way are approximately 2.69,2.40 and 1.99 eV for the samples of N2-300?,N2-400?,N2-500?,respectively.For the samples of N2-600? and N2-700?,their bandgaps are all below 1.6 eV.Experimental results show that this kind of black TiO2 nanoparticles is originated from carbon doping of TiO2.The analysis of X-ray photoelectron spectroscopy and energy spectrum shows that these samples contain carbon elements.Therefore,combining with the results of thermogravimetric analysis,we believe that this sample exhibits reduced band gap width and visible light response due to the carbon doping by the effect of the organic matter incomplete combustion under high-piurity nitrogen gas.And the "carbon source" mainly comes from two aspects:one is the complex organic matter produced after the action of anhydrous ethanol and titanium source,and the other is the surface complex formed by the combination of benzyl alcohol and TiO2.Under visible light irradiation,the black TiO2 nanoparticles are able to be photo-excited to form electrons and holes.In addition,the degree of sample doping depends on the calcination temperature and hence directly affects the photocatalytic performance.In our experiment,the sample calcined in high-purity nitrogen gas at 500? shows the best photocatalytic performance.2.According to the basic structure of perovskite solar cell,we have replaced the perovskite layer by the carbon-doped black TiO2 nanoparticles as a photosensitive layer,and have fabricated a prototype of all-solid-state TiO2 solar cell.At present,the kind of battery photoelectric conversion efficiency is still relatively low,we will try other ways to further enhance its efficiency.3.The complex TiO2 nanoparticles have been prepared by sol method,in which surface complex is formed by benzemethanol molecules and TiO2.And we further obtained the N2-200°C sample by calcining the complex TiO2 in high-purity nitrogen gas at 20? and another sample called BnOH-Modified TiO2 by modifying the complex TiO2 with benzyl alcohol.These three samples all have absorption in the visible-light region and their band gaps are 3.14,2.96,3.09 eV,respectively.In the visible-light photodegradation experiments,the complex TiO2 sample exhibits the highest photocatalytic performance.Our experimental results suggest that the surface complex formed by the LMCT interaction between benzyl alcohol molecules and TiO2 is responsible for the excellent performance.Therefore,surface modification by organic molecules such as benzyl alcohol is an efficient way to improve visible-light photocatalytic properties of TiO2 nanoparticles. |
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