【作者】 李楹；

【导师】 赵国华；

【作者基本信息】 同济大学 ， 物理化学， 2006， 硕士

【摘要】 电化学催化氧化降解有机污染物技术具有一系列其他处理方法难以比拟的优越性，研制各种高效的适用于环境污染物处理的电极是近年来国内外研究的热点。本文从改善电极表面的微观结构和修饰物种两个方面入手，制备具有纳米尺度的复合型氧化物修饰电极，以期提高催化电极的电化学性能和工作寿命，从而能够高效地催化降解环境污染物，为实用性纳米催化电极应用于环保处理提供了可靠的应用研究基础。以钛基复合氧化物电极为研究对象，通过不同的制备方法得到了具有不同表面微观结构的SnO₂+Sb₂O₅／Ti电极，同时掺杂具有良好催化性能的物质，一类为贵金属Pt和Pd，得到贵金属—非贵金属复合氧化物电极；另一类为稀土金属La、Ce、Eu、Sm，得到稀土金属—非贵金属复合氧化物电极。采用SEM和XRD技术对制备得到的各种电极表征结果表明，采用溶胶凝胶—浸渍提拉法制备得到的SnO₂+Sb₂O₅／Ti电极的平均晶粒尺寸为20nm，具有超大的电化学活性表面，掺杂Pt和Pd的SnO₂+Sb₂O₅／Ti电极的平均晶粒尺寸分别为25nm和35nm，而稀土掺杂SnO₂+Sb₂O₅／Ti电极的平均晶粒尺寸都在50nm以下，均为纳米复合氧化物电极。纳米SnO₂+Sb₂O₅／Ti电极的析氧电位在酸性、碱性和中性三种介质中分别为2.2V、1.0V、2.1V，都高于微米SnO₂+Sb₂O₅／Ti电极相对应的2.1V、0.8V、1.5V析氧电位值，尤其在中性介质中差异较大。掺杂铂、钯贵金属后，在酸性和中性介质中电极的析氧电位略有降低，其中掺铂的纳米复合电极比掺钯略为低些。掺杂稀土金属后，在酸性和中性介质中电极的析氧电位与纳米SnO₂+Sb₂O₅／Ti电极基本相同，而在碱性介质中有所提高。进一步研究还得出，若电极表面氧化物粒径由微米级达到纳米级时，复合氧化物电极在同一介质中的氧化反应传递系数β值明显增大。而掺杂贵金属、稀土金属与未掺杂的纳米SnO₂+Sb₂O₅／Ti电极相比，掺杂贵金属Pt和Pd的纳米复合氧化物电极的β值均有所增大，增大幅度为8.11％～10.71％，其中掺杂Pd的纳米复合氧化物电极的β值提高更大。掺杂稀土金属的纳米复合氧化物电极的β值也有所增大，增大幅度为6.21％～97.53％，其中掺杂Eu的纳米复合氧化物电极的β值为最高。纳米尺度的SnO₂+Sb₂O₅／Ti电极的强化寿命相比于微米尺度电极有很大的提高，是原来的3倍。进一步掺杂贵金属后，修饰电极的强化寿命可以提高到4倍；而掺杂稀土金属后，修饰电极的强化寿命可以提高到30小时左右，是未掺杂的纳米SnO₂+Sb₂O₅／Ti电极的5倍。与微米尺度电极相比，纳米SnO₂+Sb₂O₅／Ti电极对有机小分子有着较好的电催化性能，尤其是观察到了甲醛在纳米SnO₂+Sb₂O₅／Ti电极上产生的电化学振荡，这一现象有力地体现了纳米尺度效应，当氧化物粒径达到纳米尺度后，电极表面积大大增加，表面活性位点增多，催化性能增强。在掺杂贵金属的纳米SnO₂+Sb₂O₅／Ti电极上也同样发现了类似现象。有机物小分子在掺杂稀土金属的复合氧化物电极上的电化学性能表现出催化氧化的选择性，如对苯胺的电催化性能有所提高，对苯酚的电催化性能略有下降。考察了微米尺度SnO₂+Sb₂O₅／Ti电极和7种纳米复合氧化物电极对苯酚、苯胺、苯甲酸的氧化降解效果，并进行了对比。实验数据表明，纳米SnO₂+Sb₂O₅／Ti电极的相对总降解能力是微米SnO₂+Sb₂O₅／Ti电极的5倍，掺杂贵金属后基本不变，掺杂稀土金属后可进一步提高40％～60％。与微米尺度的SnO₂+Sb₂O₅／Ti电极上相比较，苯酚在纳米SnO₂+Sb₂O₅／Ti电极和掺杂稀土的SnO₂+Sb₂O₅／Ti电极上的直接电化学氧化程度较高，而掺杂贵金属的SnO₂+Sb₂O₅／Ti电极上的直接氧化的程度有所下降；但对于苯胺的电化学氧化反应，纳米尺度的复合氧化物电极的氧化降解能力未有明显地提高，这可能是因为聚苯胺的生成影响了电极的活性表面和电流效率；对于苯甲酸的电化学氧化反应，以掺杂Pt的纳米SnO₂+Sb₂O₅／Ti电极的氧化降解效果为好。本论文为进一步制备筛选适用于环境污染物电化学氧化降解地高效、实用性催化电极的研究提供了良好的理论依据。电极表面微观结构对电极催化氧化有机污染物的性能起着重要的作用，电极表面氧化物的平均晶粒尺度、掺杂的物种与电极的强化寿命以及对有机物的降解性能是紧密关联的，掺杂物种可以改变修饰层晶体的生长，从而影响晶粒的微观结构和晶粒尺度，而且可以改善锡锑氧化层和Ti基体的结合能力，提高电极的强化寿命，同时平均晶粒尺寸的减小可以增大电极的活性表面，从而提高电极的氧化降解能力。更多还原

【Abstract】 Electrochemical catalyze and oxidation of organic pollutants is one of the best and most efficient treatments and searching for the right electrode to apply in the environment treatment is popular in the recent years. Surface microstructure and modified species are two key factors according to the electrode performance. Study of the internal relation between the factors and other characters is a significative preparation of environment protecting and applied electrode products.In this paper, preparation and application of different complex metal oxide modified Ti electrodes were studied. Noble metal （Pt, Pd） and rare earth elements （La, Ce, Eu, Sm） were respectively added into SnO₂+Sb₂O₅ by different preparation methods. SEM, XRD, CV and etc. were introduced to investigate surface microstructure, electrochemical characters, serve life and electrochemical oxidation effect and the conclusions were listed below.The average crystal lattice of the SnO₂+Sb₂O₅/Ti which was prepared by sol-gel and dip-pull method is found to be 20nm, indicated a significantly increase of the electrode surface area value. The noble metal mixed SnO₂+Sb-2O₅/Ti is 25nm （Pt） and 35nm （Pd）, and the rare earth mixed SnO₂+Sb₂O-5/Ti also have a nano-structure surface as the average crystal lattice size is below 50nm.The oxygen evolution potential of micro-SnO₂+Sb₂O₅/Ti is lower than nano-SnO₂+Sb₂O₅/Ti in H₂SO₄, Na₂SO₄, NaOH medium, especially in Na₂SO₄ solution. The noble metal mixed SnO₂+Sb₂O₅/Ti is a bit lower than nano-SnO₂+Sb₂O₅/Ti in H₂SO₄ and Na2SC>4 solution and the rare earth mixed SnO₂+Sb₂O₅/Ti is higher than nano-SnO₂+Sb₂O₅/Ti in NaOH medium.The transfer coefficient 6 of oxidation at anode raised with the average crystal lattice size shrank from micro to nano.βof the noble metal mixed SnO₂+Sb₂O₅/Ti and the rare earth mixed SnO₂+Sb₂O₅/Ti is higher than nano-SnO₂+Sb₂O₅/Ti.The serve life of nano-SnO₂+Sb₂O₅/Ti greatly extended to 19 hours that is three times than the micro-SnO₂+Sb₂O-5/Ti. And the noble metal mixed SnO₂+Sb₂O₅/Ti and the rare earth mixed SnO₂+Sb₂O₅/Ti respectively extended to 23 hours and 30 hours. A significant electrochemical oscillation of formaldehyde on nano-SnO₂+Sb₂O₅/Ti was discovered. Further study indicated the electrochemical oscillation behavior is related with electrode surface area value, modified species, concentration of support electrolyte and formaldehyde, experiment temperature and etc. Similar electrochemical oscillation is also received on noble metal mixed SnO₂+Sb₂O₅/Ti and the rare earth mixed SnO₂+Sb₂O₅/Ti have good electrocatalytic property towards aniline.Electrochemical oxidation of phenol, aniline and benzoic acid on eight complex metal oxide electrodes were studied. The results showed that the total oxidation capability of nano-SnO₂+Sb₂O₅/Ti, nearly the same as noble metal mixed SnO₂+Sb₂O₅/Ti, is five times of micro-SnO₂+Sb₂O₅/Ti while the rare earth mixed SnO₂+Sb₂O₅/Ti increased 40%-60% according to the nano-SnO₂+Sb₂O₅/Ti. Phenol is mainly oxided into CO₂ and H₂O on nano-SnO₂+Sb₂O₅/Ti and rare earth mixed SnO₂+Sb₂O₅/Ti, and mainly turned into intermediate on noble metal mixed SnO₂+Sb₂O₅/Ti. Polyaniline film will cover the surface of noble metal mixed SnO₂+Sb₂O₅/Ti and benzoic acid is mainly turned into intermediate on SnO₂+Sb₂O₅+PtO/Ti.Impact factors of electrochemical characters of complex metal oxide electrodes were studied. The preparation methods were considered to be the most important factor of the electrode surface microstructure. The sol-gel and dip-pull method leads to a fine uniform nano surface. The mixed species can affect the average crystal lattice size, improve the combination between metal oxide layer and Ti, raise the serve life of the electrode. Furthermore, the reduction of the average crystal lattice size will increase the surface area value and the oxidation capability.更多还原