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Fabrication of highly efficient anodes based on structural and compositional modifications for electrochemical oxidation of recalcitrant pollutants
Sumreen Asim
Thesis Advisor王传义
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline材料物理与化学
KeywordFabrication Highly Efficient Anodes Electrochemical Oxidation Recalcitrant Pollutants

Electrochemical oxidation (EO) process is an inexpensive and effective technology for treatment of industrial sewage containing toxic organic pollutants which mainly ascribed to the reactive oxygen species (ROS). The generation of ROS strongly depends upon the microstructure, composition and physiochemical properties of the anodic materials. Nanostructured highly porous 3D–Ti/Sb–SnO2–Gr electrode, based on 3D porous graphene hydrogel is fabricated via a fast-evaporation technique through layer by layer (LBL) deposition. The fabricated 3D porous electrode possesses high oxygen evolution potential (2.40 V), higher porosity (0.90), enhanced roughness factor (181), and larger voltammetric charge value (57.4 mC cm-2). EO of Rhodamine B (RhB) is employed to evaluate the efficiency, the rate constant (k) value of 4.93 10-2 min-1 is obtained which is 3.91 times higher than the traditional Ti/Sb–SnO2. Moreover, the mineralization of 2, 4–DCP by using nanostructured 3D–porous Ti/Sb–SnO2–Gr anode is also investigated. Within 40min of reaction, 99% of removal rate is achieved, meanwhile, 81% of TOC removal is recorded with lowest SECTOC of 62.25 KWh (kg TOC) –1 at maximum MCE% (246%). For understanding the pathway of 2, 4–DCP degradation, the intermediates are tested through HPLC and UPLC/MS-MS, showing a complete mineralization.Furthermore, a simple template removal method has been reported for fabrication of two different kinds of hierarchically porous architectures, Ti/Sb-SnO2-honeycomb (honeycomb) and Ti/Sb-SnO2-network (network) with remarkable porosity and layer by layer arrangement in multiple directions. The honeycomb and network possess high OEP value upto 2.60 V and 2.76 V, with 7.46 mC cm-2 and 11.96 mC cm-2 total voltammetric charge compared to the conventional one (3.0 mC cm-2), which indicates the significant enhancement in electrochemical active sites. The mechanistic study suggests that more electro active sites provided by hierarchically porous electrodes lead to accelerate HO? generation and the channels of porous structure significantly promotes the adsorption and diffusion of pollutant molecules.In addition, high-performance catalyst in terms of reactivity, selectivity with long time activation, noble metal-metal oxide nanocomposites (NMMOs) is synthesized by using micro emulsion technique. Encapsulation of Pt within MOs shell is successfully obtained which simultaneously prevent the direct exposure of NM as well as intimate a 3D contact between NM and MOs is developed which provided larger interfacial interaction leading to strengthen its reactivity. The EO of PFOA is employed to explore the catalytic activity of Pt@MO nanoparticles, and the obtained results showed that PFOA is completely degraded within 6 h while the traditional Pt-MO showed only 20% of degradation. The quantitative measurements of stable intermediates during the mineralization were carried out by UPLC/MS-MS to reveal the complete mineralization as well as the stability was also estimated to figure out its practical usage.All fabricated electrodes demonstrate superior advantages over the traditional once such as better electrocatalytic performance, higher stability, low energy consumption and efficient mineralization of organic water pollutants. It is expected that this work can be a promising approach towards practical usage for recalcitrant pollutant incineration.

Other Abstract

电化学氧化技术是一种成本低、效率高的有毒废水处理技术。电化学氧化技术的核心是高活性自由基的产生,而自由基的生成取决于阳极材料的微观结构、组成以及物理化学性质。高孔隙率的纳米结构 3D–Ti/Sb–SnO2–Gr 阳极是采用快速蒸发法制备的三维石墨烯水凝胶为模板,通过层层沉积的方式制备而成的。所制备的三维多孔电极有较高的析氧过电位(2.40 V)、孔隙率(0.90)、表面粗糙因子(181)和较大的伏安电荷值(57.4 mC cm-2)。以罗丹明B为模型污染物对所制备电极的电催化氧化效率进行了评价。实验结果表明相比于传统的Ti/Sb–SnO2电极,三维多孔 Ti/Sb–SnO2–Gr电极表现出较高的反应速率4.93*10-2 min-1。此外,也进行了三维多孔 Ti/Sb–SnO2–Gr电极矿化2, 4–DCP的实验。结果表明,在40分钟的反应时间内,99%的2, 4–DCP被降解,同时TOC去除率也达到81%,此外SECTOC值为62.25 KWh (kg TOC) –1,同时最大MCE%值为246%。为了理解2, 4–DCP的降解和矿化过程机理,采用HPLC和 UPLC/MS-MS对反应过程的中间体进行了检测。另外,采用简单的模板法制备了两种不同类型的多级孔结构电极材料,分别为蜂窝状和蛛网状 Ti/Sb-SnO2电极,这两种电极具有丰富的孔结构和层层组装。这种蜂窝状和蛛网状 Ti/Sb-SnO2电极的析氧过电位分别为2.60 V和 2.76 V,伏安电荷值为7.46 mC cm-2 和 11.96 mC cm-2。机理研究表明,这种蜂窝状和蛛网状的多级孔结构可以产生更多的表面活性位点,从而加快羟基自由基的产生以及污染物分子在孔道结构中的传质,从而增强电催化氧化效率。此外,我们采用乳液法合成了具有高活性和选择性的Pt-IrO2-RuO2复合阳极材料。通过将Pt包覆于金属氧化物内部,增加Pt与金属氧化物的接触,从而增强电极的电催化氧化性能。通过电催化氧化降解PFOA来评价Pt-IrO2-RuO2复合阳极材料的性能。结果表明,乳液法制备的Pt-IrO2-RuO2复合阳极材料可以在6h完全降解PFOA,而传统方法制备的Pt-IrO2-RuO2复合阳极材料仅能降解20%。采用UPLC/MS-MS 检测了PFOA降解中间产物,从而理解了其降解机理。本论文通过研究电极材料的结构和组成对于电极性能的影响,提出了针对传统电极材料性能的改善方法,可以获得具有高催化活性、高稳定性、低能耗的电极材料。

Document Type学位论文
Recommended Citation
GB/T 7714
Sumreen Asim. Fabrication of highly efficient anodes based on structural and compositional modifications for electrochemical oxidation of recalcitrant pollutants[D]. 北京. 中国科学院大学,2016.
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