【作者】 万斌；

【导师】 沈嘉年；

【作者基本信息】 上海大学 ， 材料学， 2008， 博士

【摘要】 本文研究了阳极氧化法制备TiO₂纳米管的工艺及TiO₂纳米管在紫外光下的光催化性能,进而研究了Ag光催化还原、N掺杂对TiO₂纳米管紫外光及可见光下的光电催化性能的影响。本论文首先研究了氧化电压、溶液组成及pH值、反应时间和退火温度对TiO₂纳米管形貌的影响。通过SEM、XRD、BET等测试对所制备的纳米管的结构、形貌进行了表征。研究表明:阳极氧化电压是影响TiO₂纳米管出现和尺寸的最重要因素,当电压为20V时,纳米管排列最有规则;电解液的组成不同,溶液pH值不同,因此不同体系中TiO₂纳米管的长度与氧化时间的关系不同,在HF体系中,20min之后,TiO₂纳米管的长度随时间的变化不显著,只有500nm,在HF+NH₄H₂PO₄溶液中纳米管长到2.2μm需要15小时,NaF+Na₂SO₄溶液中TiO₂纳米管长到2.2μm只需要4-6小时:阳极氧化法制备的TiO₂纳米管是无定型结构,250℃退火出现锐钛矿结构,500℃退火是锐钛矿为主的锐钛矿和金红石矿的混晶,600℃退火是金红石矿为主的金红石与锐钛矿的混晶。通过研究不同条件下酸性红G紫外光下光催化降解效率,确定了具有最佳光催化性能TiO₂纳米管的阳极氧化制备工艺,即:0.5（wt）%NaF+1mol/LNa₂SO₄体系中,阳极氧化的电压为20V,反应时间为6h,在500℃的空气气氛下退火1h;同时该方法制备的TiO₂纳米管最佳偏压值为0.45V（vs.SCE）。以该工艺制备的TiO₂纳米管为阳极,施加0.45V（vs.SCE）偏压下,pH=3,初始浓度为20×10^-6的酸性红G,经过5个小时的紫外光照射后,光电催化降解率约为92.4%。在以上实验基础上,首次采用光催化还原法在AgNO₃溶液中将纳米尺度的Ag单质沉积在阳极氧化制备TiO₂纳米管表面。通过SEM、XRD、XPS等测试对所制备纳米管的结构、形貌进行了表征。结果显示:Ag是以单质的形式,尺寸从10-100nm不等,不均匀地分布在纳米管表面,并具有很好地化学稳定性。TiO₂纳米管紫外光的光降解效率随Ag含量的增加而增加,但是当Ag含量超过最佳值后,光降解效率反而下降,实验结果表明Ag含量在1.15（wt）%时光催化效率最高。Ag含量为1.15（wt）%的Ag/TiO₂纳米管电极的光催化降解亚甲基蓝的效率比TiO₂纳米管电极的光催化效率提高了约22.98%,降解三小时后,初始浓度为10×10^-6的亚甲基蓝溶液COD降解率达到95%。将阳极氧化制备的TiO₂纳米管浸泡在氨水中再退火进行N掺杂,XPS测试显示N是以置换的形式进入到纳米管晶格的,成功地制备了TiO_2-xN_x纳米管,UV-vis测试显示N掺杂后TiO₂纳米管的吸收带边发生明显红移。首次对该法制备的TiO_2-xN_x纳米管施加偏压,提高其在可见光下光电催化性能;N含量为0.53（wt）%的TiO_2-xN_x纳米管为阳极,施加0.45V（vs.SCE）偏压,在可见光下光电催化降解初始浓度为10×10^-6的亚甲基蓝16小时效率为55.3%。采用光催化还原的方法,在AgNO₃溶液中将Ag沉积到上述方法制备的TiO_2-xN_x纳米管表面,首次实现N掺杂、Ag沉积共同对阳极氧化制备的TiO₂纳米管进行改性,成功制备出不仅能显著提高紫外光光催化效率,而且在可见光下具有光电催化性能的Ag/TiO_2-xN_x纳米管。Ag/TiO_2-xN_x纳米管可见光下16小时光电催化降解10×10^-6的亚甲基蓝和20×10^-6的酸性红G效率分别为63.5%和25.2%。表明该法制备的Ag/TiO_2-xN_x纳米管对有机物溶液的光催化降解具有普遍适用性。更多还原

【Abstract】 The technics of preparion TiO₂ nanotube by anodizing and photocatalytic performance under UV-light of TiO₂ nanotube have been studied in detail in this dissertation.Modification of TiO₂ nanotube by doping Ag,N and influence on its photocatalytic property under both UV-light and visible light were also discussed.The influence of preparation parameters including oxidation voltage,the composition of electrolyte,pH value,oxidation time and annealing temperature on stmction,morphology of TiO₂ nanotube were systematically evaluated.The samples were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM） and specific area were measured by BET test instrument.The results show:oxidation voltage is the most important factor to control the appearance and sizes of TiO₂ nanotube,at voltage of 20V,array of TiO₂ nanotube with well ordered morphology can be produced.In different electrolyte,the pH value is different,so relationship between length of nanotube and time is not the same.In electrolyte of HF,after 20min,the length of nanotube is not grow as reaction continue and only reaches to 500nm.In electrolyte of HF+NH₄H₂PO₄ and NaF+Na₂SO₄,it needs 15h and 4-6h respectively to reach 2.2μm.TiO₂ nanotube prepared by anodizing is amorphous phase,after annealed at 250℃,anatase phase appears,the anatase phase is the predominant phase at 500℃annealing,and further heating of 600℃,the mixed crystal with the rutile phase is the predominant phase can be get.By study photo-degradation behavior of acid red G under UV-light with the prepared TiO₂ nanotube electrode in different experiment condition,shows that the best prepare condition for the growth of TiO₂ nanotube is:in electrolyte of 0.5（wt） %NaF +1mol/L Na₂SO₄,at 20V,reaction time is 6h,then annealed in air at 500℃for lh.The applied bias TiO₂ nanotube prepared by this process is 0.45V（vs.SCE）. After 5 h of UV irradiation（pH=3,using TiO₂ nanotube electrode）,the degradation rate of acid red G about 20×10^-6mol/L was 92.4%. Basing on these work,in electrolyte of AgNO₃,Ag nanoparticles were deposited photocatalytically on the TiO₂ nanotube surface,for the first time.The samples were characterized by XRD,SEM and X-ray Photoelectron Spectroscopy（XPS）.The results show:Ag particles（from 10nm-100nm） are deposited on TiO₂ nanotube surface un-uniformly,exist as Ag⁰,and Ag particles show good chemical stability.The photo-degradation rate of mathylene bule solution increases as content of Ag loaded on nanotube surface increases,if content greater then the most optimum content,photo-degradation rate will decrease.Experiment shows that the optimum content of Ag is about 1.15（wt）%.The Ag loaded nanotubes have much higher photo-degradation rate than un-loaded nanotubes,increases about 22.98%,After 3 h of UV irradiation of mathylene bule 10×10^-6mol/L,the degradation rate of chemical oxygen demand（COD） is about 95%.Nitrogen-doped TiO₂ nanotube array was fabricated by anodizing followed imme -rsed into liquid ammonia and anneal process.XPS result indicates that the nitrogen atoms were doped into lattice of TiO₂ nanotubes.The UV-ViS spectra shows that the photo-absorption of N-doped TiO₂ nanotube is enhanced in the visible light region. The bias was applied to improve photocatalytic property of N-doped TiO₂ nanotube under visible light for the first time.Using N-doped TiO₂ nanotube（Nitrogen content is 0.53（wt）%） as anode,after 16h of irradiation under visible light,the degradation rate of mathylene bule about 10×10^-6mol/L is 55.3%with 0.45V（vs.SC E） bias.Ag nanoparticles were deposited photocatalyticaUy on the N-doped TiO₂ nano -tube surface,modification of TiO₂ nanotube by Ag,N co-dope was made for the first time.Results show Ag/TiO_2-xN_x nanotube not only can improve photodegradation performance under UV-light,but also has photodegradation performance under visible light.After 16h of irradiation under visible light,the photoeleccatalytic degradation rate of mathylene bule(10×10^-6mol/L) and acid red G(20×10^-6mol/L) is 63.5%and 25.2%respectively with 0.45V（vs.SC E） bias.The result shows Ag/TiO_2-xN_x nanotube made in this dissertation is applicable for organic solution universally.更多还原