【作者】 刘冬；

【导师】 孙卓； 聂耳；

【作者基本信息】 华东师范大学 ， 材料与光电子， 2019， 博士

【摘要】 随着社会的发展、工业化进程的加速,大量排放的有机污染物所引起的水污染问题越来越严重。在受污染水体中,以染料、化工用品和药物等有机污染物较为常见。光电催化（photoelectrocatalytic,PEC）作为一种新型的高级氧化技术,能够氧化分解绝大多数难降解的有机污染物,具有设备简单、条件温和以及无二次污染等突出优点,在环境领域中受到了广泛关注。在众多催化剂中,由于TiO₂具有成本低、毒性小、化学稳定性好等优点,被认为是PEC技术中最具应用潜力的光电阳极催化剂。然而,PEC技术还存在一些问题,例如,TiO₂薄膜电极的可见光利用率低、制备成本高和稳定性差等,限制了其在污水处理中的产业化应用。现有与PEC相关的研究报道主要集中在材料表征和催化剂降解性能等方面,而对其降解机理方面的研究尚不充分。鉴于此,开发简单、低成本的方法制备具有高可见光催化性能的TiO₂薄膜电极以及研究PEC降解机理具有重要意义。由于卤素（F和I）掺杂TiO₂制备方法简单,并具有优异的可见光催化性能,是制备PEC光电阳极的理想催化剂。在本论文中,为了解决PEC技术中存在的问题,我们采用简单的方法（溶胶-凝胶法和水解法）制备了具有优异可见光催化活性的卤素掺杂TiO₂催化剂。然后,采用简单、低成本的丝网印刷法制备了卤素掺杂TiO₂薄膜电极,该电极在可见光照射下对有机污染物表现出了较高的PEC降解性能,并具有良好的稳定性。同时,也对PEC过程中有机污染物的降解机理进行了分析。论文具体内容如下:1.采用简单的溶胶-凝胶法和水解法成功制备了卤素掺杂TiO₂催化剂,并对该催化剂进行了物理化学表征。结果表明,卤素（F和I）掺杂和多元素（F-Sn和I-P）共掺杂能够明显提升TiO₂的可见光吸收能力和光生电荷分离速率。然后,以FTO导电玻璃为催化剂载体,采用丝网印刷法制备了具有多孔形貌的卤素掺杂TiO₂薄膜电极。为了解决催化剂易从FTO基体脱落的问题,在电极制备过程中添加了低温玻璃粉来增强催化剂与导电基体间的附着性。2.选取污水中常见的有机污染物（亚甲基蓝、苯酚、双氯芬酸和四环素）以及实际废水（垃圾渗滤液和制药废水）作为降解对象,评估了卤素掺杂TiO₂薄膜电极对有机污染物的PEC降解性能。结果表明,电极在可见光照射下对有机污染物和实际废水均表现出良好且稳定的PEC降解性能,并且该PEC性能受元素掺杂量、外加偏压、溶液pH、H₂O₂浓度和电解质种类等因素的影响。另外,在卤素掺杂TiO₂薄膜电极中,I,P共掺杂TiO₂薄膜电极对有机污染物表现出了最高的PEC降解性能。3.采用了一级动力学模型、Langmuir-Hinshelwood动力学模型以及活性粒子捕获实验对卤素掺杂TiO₂薄膜电极PEC降解有机污染物的机理进行了分析。结果表明,有机污染物的PEC降解过程主要发生在薄膜电极表面,并且电极表面对有机污染物的吸附是降解过程中的限速步骤。在有机污染物的PEC降解过程中,空穴（h⁺）和羟基自由基（.OH）是引起有机污染物降解的主要活性粒子,并且元素掺杂量和有机污染物起始浓度不会影响h⁺和.OH的主导地位。当NaCl为溶液电解质时,有机污染物的PEC降解速率会明显提升,h⁺和.OH会与溶液中的Cl^-反应生成大量的氯自由基（Cl.）并参与有机污染物的降解。此条件下,Cl.是降解有机污染物的主要活性粒子。另外,对有机污染物的PEC降解路径研究再一次证实,h⁺和.OH在有机污染物的PEC降解过程中发挥了主导作用。更多还原

【Abstract】 With the development of society and the acceleration of industrialization,water pollution caused by huge amounts of organic contaminants is becoming more and more serious.Dyes,chemicals and pharmaceuticals are the main common recalcitrant organic pollutants in the polluted water.The photoelectrocatalytic（PEC）is a new type of advanced oxidation technology,which can degrade most kinds of refractory organic contaminants.The PEC technology has attracted increasing attention in environmental area,due to its advantages of simple equipment,mild operation conditions and no secondary pollution.Among the numerous catalysts,TiO₂ is considered to be the most promising catalyst to fabricate the photoanode for its advantages of low cost,low toxicity and high chemical stability.However,some issues still exist in the PEC technology,such as low visible utilization efficiency,high preparation cost and poor stability of TiO₂ film photoelectrode,which restrict its industrial application in the wastewater treatment.In addition,recent studies on PEC degradation of organic contaminants mainly focus on the characterization and catalytic performance of the catalyst,but the degradation mechanism has not been adequately studied.Therefore,it is significant to develop a simple preparation method of TiO₂ film photoelectrode with low cost and high visible PEC performance,as well as to investagtae the PEC degradation mechanism of organic contaminants.Halogen（F and I）doped TiO₂ is the optimal catalyst to fabricate the photoelectrode due to its simple preparation method and excellent visible photocatalytic activity.In this thesis,in order to solve the problems above,the halogen doped TiO₂ catalysts were synthesized via simple methods（sol-gel and hydrolysis methods）,exhibiting an excellent visible light catalytic activity.The halogen doped TiO₂ film photoelectrodes which were prepared by the screen printing method showed high PEC degradation efficiency of organic contaminants under visible light irradiation.In addition,the photoelectrodes also exhibited excellent stability.Meanwhile,the PEC degradation mechanisms of organic contaminants were also investigated.The details of this thesis are as follows:1.The halogen doped TiO₂ catalysts were successfully synthesized by the simple sel-gel and hydrolysis methods,and they were characterized by the physical and chemical analyses.The results indicated that the visible absorption ability and photogenerated charges separation rate of TiO₂ were significantly enhanced by halogen（F and I）doping and multielement（F-Sn and I-P）co-doping.Then,an FTO glass was chosen as the conductive substrate of catalysts and the halogen doped TiO₂ film photoelectrodes were prepared by a simple screen-printing method.In order to inhibit the detachment of catalysts from the FTO substrate,low melting-point glass powders were added during the photoelectrode preparation process to enhance the attachment between the catalysts and FTO substrate.2.The common organic contaminants（methylene blue,phenol,diclofenac and tetracycline）and wastewater（landfill leachate and pharmaceutical wastewater）were chosen to evaluate the PEC performance of the halogen doped TiO₂ film photoelectrodes.The results suggested that the photoelectrodes exhibited an excellent PEC performance in the degradation of organic contaminants and wastewater under visible light irradiation.And the PEC performance was affected by the element doping content,applied bias,pH of solution,concentration of H₂O₂ and type of electrolytes.In addition,among the halogen doped film photoelectrodes,the I,P co-doped film photoelectrodes showed the highest PEC performance.3.The PEC degradation mechanisms of organic contaminants were investigated by the first-order kinetic model,Langmuir-Hinshelwood kinetic model and active species trapping experiments.The results implied that the PEC degradation of organic contaminants mainly occurred on the surface of halogen doped photoelectrodes,and the surface adsorption was the controlling factor in the organic contaminants degradation process.In the PEC process,holes（h⁺）and hydroxyl radicals（.OH）were the major active species contributing to the decomposition of organic contaminants,and the dominant roles of h⁺and.OH were not significantly affected by the element doping content and initial concentration of organic contaminants.The degradation rate of organic contaminants could be significantly enhanced under the condition of high Cl^-concentration,which was caused by the participation of chloride radicals（Cl.,created by h⁺and.OH）in the PEC process.Under this condition,the organic contaminants were mainly degraded by the Cl..In addition,the dominant roles of h⁺and.OH in the PEC process were further demonstrated by the investigation of PEC degradation pathways of organic contaminants.更多还原