电聚合制备聚苯胺@石墨毡复合电极及其在电芬顿过程中的高效电催化性能（英文）

发布时间：2018-07-13 09:11

【摘要】：作为一种高级氧化技术(AOPs),芬顿氧化法(Fenton)因其操作简单、绿色高效而备受关注.其基本原理是Fe~(2+)催化H_2O_2产生的羟基自由基(·OH)进攻有机物使之降解为无机小分子或盐.电芬顿法(Electro-Fenton,E-Fenton)是利用电化学方法原位生成H_2O_2的Fenton衍生法,其优点在于不需要从外界加入H_2O_2、高效节能、无选择性、并且易于和其他处理技术耦合,是一种非常有价值和应用前景的新型水处理技术.电芬顿技术的理论探究和工艺优化,是当今高级氧化技术的理论和实践研究的重要内容.E-Fenton过程的关键步骤是阴极材料上氧还原反应(Oxygen reduction reaction,ORR)持续生成H_2O_2.由于析氢过电位高、稳定性好、性能优异,碳材料成为ORR反应最常用的电催化阴极材料.石墨毡作为一种三维多孔立体材料,具有电化学活性面积大、传质好、导电性强、价格低等优点,是ORR的理想阴极材料.聚苯胺材料作为一种导电高分子材料,价格便宜、加工性好、且含有丰富的N原子,在基础研究和实际应用领域都十分活跃.我们创新性地采用电聚合的方法合成了聚苯胺@石墨毡(PANI@GF)复合电极,并通过降解邻苯二甲酸二甲酯(dimethyl phthalate,DMP)研究了其在电芬顿过程中的电催化性能.通过扫描电镜、X射线光电子能谱分析对电极表面结构和杂原子掺杂性进行了物化表征.结果显示PANI@GF复合电极同时具有宏观和微观的三维多孔结构,这种结构蓬松的多孔结构为氧气提供了合适的传递通道和足够的反应面积.所制备复合电极中N原子含量约为1.9%,且吡啶N和吡咯N的含量相对较高.这些N原子来自聚苯胺分子中含有的大量N原子,并能够促进ORR反应.石墨毡和聚苯胺两种材料的在结构和组分上的特点,使得PANI@GF复合电极具有优异的电芬顿降解DMP的性能.在DMP浓度为50 mg/L、电位0.5 V(vs.SCE)、氧气流速为0.4 L/min的条件下,其DMP降解反应表观动力学常数达0.0753 min-1,是石墨毡电极表观动力学常数(0.0151 min-1)的5倍.PANI@GF复合电极制备的最优聚合时间和碳化温度分别为1 h和900°C.这是因为聚合时间太长,可能导致聚苯胺层厚度大,微孔结构被堵塞,进而降低了反应活性面积和影响氧气传质效果,使得电极性能下降;而聚合时间太短,可能导致电极复合不充分.高温碳化可以使石墨毡表面聚苯胺层形成更多的孔结构,从而有利于ORR过程.DMP降解过程中氧气流速、Fe~(2+)用量以及p H值等工艺条件对电极性能有一定的影响,结果表明其相应的优化值分别为0.4 L/min、1.0 mmol/L和3.0.当氧气流速过低时,溶液中低浓度的溶解氧使ORR过程受传质过程限制,导致电极不能充分反应;当氧气流速过大时,并不会增加已经达到饱和的溶液中的氧气浓度,而过大的氧气速率会冲击电极表面,降低电极稳定性而影响其催化性能.对Fe~(2+).用量而言,E-Fenton过程有多种Fe循环途径,不同的铁含量对于电极性能影响不明显.因此,1.0 mmol/L的Fe含量足够满足实验需要.p H值对E-Fenton过程至关重要,p H较高时,铁离子会形成配合物,阻碍铁循环,并且会导致H_2O_2的分解,从而降低电极DMP降解性能;而当p H太低时,较多的酸增加成本,且需要后续处理过程以消除酸的影响.实验结果表明3.0是最优p H值,与传统Fenton方法的最适p H相符.PANI@GF复合电极具有高效催化降解DMP的能力,在电芬顿技术处理有机废水中有潜在应用.
[Abstract]:As a advanced oxidation technology (AOPs), Fenton oxidation (Fenton) has attracted much attention because of its simple operation and green efficiency. The basic principle is that Fe~ (2+) catalyzes the hydroxyl radical (. OH) attack of organic matter produced by Fe~ (2+) to degrade it into inorganic small molecules or salts. The electric Fenton method (Electro-Fenton, E-Fenton) is in situ formation by electrochemical method. The advantage of H_2O_2's Fenton derivation is that it does not need to add H_2O_2 from the outside world, it is efficient, energy saving, no selectivity, and is easy to be coupled with other processing techniques. It is a new water treatment technology with great value and application prospect. Theory and process optimization of electric Fenton Technology are the theoretical and practical research of advanced oxidation technology. The key step of the.E-Fenton process is that the oxygen reduction reaction on the cathode material (Oxygen reduction reaction, ORR) continues to produce H_2O_2. because of high hydrogen evolution overpotential, good stability and excellent performance. Carbon materials become the most commonly used electrocatalytic cathode materials for ORR reaction. As a three-dimensional porous solid material, graphite felt has electrochemistry. With the advantages of large active area, good mass transfer, strong conductivity and low price, it is an ideal cathode material for ORR. Polyaniline material is a kind of conductive polymer material, which is cheap, good processing and rich in N atoms. It is very active in the field of basic research and practical application. We have synthesized polyaniline by electropolymerization. The electrocatalytic properties of the @ graphite felt (PANI@GF) composite electrode were studied by degradation of two methyl phthalate (dimethyl phthalate, DMP). The surface structure of the electrode and the doping of the heteroatom were characterized by the scanning electron microscopy (SEM) and the X ray photoelectron spectroscopy analysis. The results showed that the PANI@GF composite electrode was at the same time. The porous structure with macroscopic and microscopic structure, the porous structure of this fluffy structure provides the appropriate transfer channel and sufficient reaction area for oxygen. The N atom content in the prepared composite electrode is about 1.9%, and the content of pyridine N and pyrrole N is relatively high. These N atoms are derived from a large number of N atoms in the polyaniline molecules and can be promoted. The ORR reaction. The structure and composition of two materials of graphite felt and polyaniline made the PANI@GF composite electrode have excellent electrical Fenton degradation of DMP. Under the condition of DMP concentration of 50 mg/L, potential 0.5 V (vs.SCE), and oxygen flow rate of 0.4 L/min, the reverse apparent kinetic constant of DMP degradation is 0.0753 min-1, and it is the graphite felt electricity. The optimal polymerization time and carbonization temperature of the 5 times.PANI@GF composite electrode of the polar kinetic constant (0.0151 min-1) are 1 h and 900 C., respectively, because the polymerization time is too long, which may lead to the large thickness of the polyaniline layer and the microporous structure being blocked, thus reducing the reactive area and affecting the mass transfer effect of oxygen, making the electrode performance under performance. When the polymerization time is too short, it may lead to the insufficient composite of the electrode. High temperature carbonization can make the polyaniline layer on the surface of the graphite felt more pore structure, which is beneficial to the oxygen flow velocity in the process of ORR.DMP degradation, the amount of Fe~ (2+) and the p H value have a certain influence on the electrode property. The results show the corresponding optimum value. When oxygen flow is too low for 0.4 L/min, 1 mmol/L, and 3.0., the low concentration of dissolved oxygen in the solution limits the ORR process by the mass transfer process, causing the electrode to not fully react; when the oxygen flow is too high, it does not increase the oxygen concentration in the saturated solution, and the excessive oxygen rate will impact the electrode surface and reduce the electrode surface. For Fe~ (2+). For the dosage of Fe~ (2+), there are many Fe cycles in the process, and the different iron content has no obvious influence on the performance of the electrode. Therefore, the content of 1 mmol/L is sufficient to satisfy the experimental needs of the.P H value for the E-Fenton process, and when p H is higher, the iron ions will form a complex, hindering the iron cycle, and And it will lead to the decomposition of H_2O_2 and reduce the degradation performance of the electrode DMP, and when the P H is too low, more acid increases the cost, and the subsequent treatment process is needed to eliminate the effect of acid. The experimental results show that 3 is the best p H value, and the.PANI@GF composite electrode of the most suitable P H of the traditional Fenton method has the ability to catalyze the degradation of DMP, and in the finen. It has potential applications in the treatment of organic wastewater.
【作者单位】：广东省低碳化学与过程节能重点实验室中山大学材料科学与工程学院;中山大学化学工程与技术学院;
【基金】：supported by the Sino-Greek Science and Technology Cooperation Project (2013DFG62590) the National Natural Science Foundation of China (21575299, 21576300, 21276290) Guangdong Province Nature Science Foundation (2014A030313150) Guangzhou Science and Technology Plan Project (201607010104)~~
【分类号】：O646.54;O643.3

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