【作者】 韩蕾；

【导师】 刘惠玲；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 博士

【摘要】 本论文针对TiO₂催化剂对太阳光利用率低的问题,采用阳极氧化法制备出TiO₂/Ti光电极,并通过镧元素和氮元素的掺杂制备出改性的La-TiO₂/Ti和N-TiO₂/Ti光电极,拓展了TiO₂对可见光的响应范围,同时对水中内分泌干扰素类物质-甲草胺的去除性能进行了研究。与常用的溶胶-凝胶法相比,阳极氧化法具有操作工艺简单、膜与基体结合牢固、不易脱落、膜层均匀等优点。在阳极氧化的过程中,通过向H₂SO₄电解质溶液中添加La（NO₃）₃的形式制备镧掺杂的TiO₂/Ti光电极,并对工艺条件进行了优化,重点考察了掺杂物的浓度、电压对改性TiO₂/Ti光电极性能的影响,其最佳的制备条件为制备电压160V,La（NO₃）₃的浓度为800mg/L。针对在制备电极的氧化过程中进行氮的掺杂较为困难,含氮化合物很难直接进入到TiO₂膜层中的问题,采用等离子体基离子注入技术（PII）,以阳极氧化法制备的TiO₂/Ti光电极为基体,制备了氮掺杂的TiO₂/Ti光电极,其最佳的制备条件为制备电压160V ,离子注入电压-30KV ,注氮剂量4×10¹⁵N/cm²。利用扫描电镜（SEM）、原子力显微镜（AFM）、X-射线衍射光谱（XRD）、X-射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）、表面光电压谱（SPS）和电化学的方法等分析手段,对掺杂前后所得TiO₂/Ti光电极表面形貌、晶体结构、晶粒大小、表面成分和化学形态、吸收光谱、表面光电性能等进行了分析。研究结果表明,镧元素在TiO₂薄膜的表面以La2O3的形式存在,在界面处钛原子代替氧化镧晶格中的镧原子,形成Ti-O-La的键合;氮元素主要以三种形态存在于TiO₂的晶格或分子间隙之中,即β-N、γ-N和O-Ti-N。两种改性的TiO₂/Ti光电极对可见光的响应范围都有所提高,相对于未改性的TiO₂/Ti光电极,二者对染料废水的代表物质-罗丹明B的降解效果较好。用氮掺杂TiO₂/Ti光电极对饮用水中的内分泌干扰物质-甲草胺的光电催化氧化过程进行了研究,建立了准一级动力学模型。研究的结果显示,影响甲草胺光电催化降解的因素由强至弱的顺序为:光源的辐照强度>催化剂的面积>甲草胺的初始浓度>外加偏压。运用第一性原理对氮掺杂TiO₂/Ti光电极的能带结构进行了研究,计算结果表明氮掺杂后TiO₂的能带结构中产生了杂质能级,使其禁带宽度变窄,从而导致TiO₂吸收光谱的红移,计算结果与实验值符合较好。通过电助光催化的方法研究了恒电流法和恒电压法对甲草胺的降解效率,并证实了在光催化和电催化之间存在协同效应,反应溶液中加入Na₂SO₄电解质后,SO₄^2-可以被价带空穴氧化成强氧化性的S₂O₈^2-,继而可以氧化处理物质,提高甲草胺的降解效率。利用荧光法研究了TiO₂/Ti光电极光电催化降解过程中·OH的生成规律。采用液-质联机（LC-MS）对甲草胺光电催化降解过程中的中间产物进行了分析。实验的结果表明:甲草胺在羟基自由基的作用下通过羟基化作用和脱烷作用,发生断键、开环等一系列的氧化还原反应,最终生成CO₂和H₂O等无机小分子物质。更多还原

【Abstract】 The present work aimed to prepare TiO₂/Ti photoelectrode by means of anodic oxidation to solve the problem for low efficiency to solar of TiO₂ catalyst. La doped and N-doped TiO₂/Ti photoelectrodes were prepared via incorporation of lanthanum and nitrogen, respectively, which could extend the response of TiO₂ to visible light. The present work also investigated the degradation of endocrine disrupting chemicals-alachlor.Compared to sol-gel method, anodic oxidation was simple, and the film was uniform and it is hard to detach and combined firmly with the substrate. La-doped TiO₂/Ti photoelectrodes can be prepared and optimized by anodization, in situ formation of TiO₂ film on titanium substrate in the mixed solution of H2SO4 and La（NO₃）₃ . The preparation parameters, such as the concentration of dopants and voltage, were optimized. The La（NO₃）₃ concentration of 800 mg/L and the voltage of 160 V are the optimal conditions for preparation of La-doped TiO₂/Ti photoelectrodes.With respect to the fact that doping of nitrogen and nitrogen compounds is difficult to enter directly into the TiO₂ film in the anodic oxidation process, the N-doped TiO₂/Ti photoelectrode was prepared on TiO₂/Ti photoelectrode substrate by Plasma based ion implantation（PII） method. The optimal preparation conditions were preparation voltage 160 V, implantation voltage 30 KV and the doing content 4×10¹⁵ N/cm², respectively.By using scanning electron microscopy （SEM）, atomic force microscope （AFM）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, UV-Vis diffuse reflectance spectroscopy （UV-vis DRS）, surface photovoltage spectroscopy （SPS） and electrochemical methods and other methods, the doped and undoped TiO₂/Ti photoelectrode surface morphology, crystal structure, grain size, surface composition and chemical form, absorption spectra, surface optical properties were analyzed. The results showed that lanthanum at the surface of TiO₂ film was in the form of La₂O₃, and in the interface titanium atoms replaced lanthanum atoms in the lattice of lanthanum oxide to form Ti-O-La bonding; Three kinds of nitrogen existed in the TiO₂ lattice or molecular gap among theβ-N,γ-N, and O-Ti-N. The reposes of two modified TiO₂/Ti to visible light were superior to that of unmodified TiO₂/Ti and the degradation of Rhodamine B was better for modified TiO₂/Ti than that of unmodified TiO₂/Ti photoelectrode.N-doped TiO₂/Ti photoelectrode were used for the photocatalytic oxidation of endocrine disrupting chemicals-alachlor whose photocatalytic oxidation process was proved to be pseudo first order kinetic. The results showed that the influencing factors of alachlor degradation were in the following orders: light irradiation intensity>catalyst area> catalyst initial concentration of alachlor>external bias. The energy band structure of N-doped anatase TiO₂ was studied by first principles. The calculation revealed that impurity energy level was generated in the energy band of TiO₂ after the incorporation of nitrogen, which resulted in a narrower band gap and a red shift of the absorption spectra of TiO₂. The calculating result was in good agreement with experimental data.The electro-assisted photocatalytic efficiency for the degradation of alachlor was studied by means of potentiostatic and galvanostatic models, whose results confirmed the synergistic effect between the photocatalysis and electrocatalysis. When Na₂SO₄ electrolyte was added into the reaction solution, the SO₄^2- can be oxidized by strong valence band hole to S₂O₈^2-, which could improve the degradation efficiency of alachlor. The·OH generation in the process of TiO₂/Ti photocatalytic degradation was studied by fluorescence method, and the intermediate products were analyzed by liquid chromatography-mass line （LC-MS） in the course of alachlor degradation. Experimental results showed that a series of redox reactions including bond-breaking and ring-open of alachlor took place via hydroxylation and dealkylation under the force of hydroxyl radicals. Eventually, this kind of organic compound was decomposed into inorganic molecules such as CO₂ and H₂O.更多还原