【作者】 高明明；

【导师】 杨凤林；

【作者基本信息】 大连理工大学 ， 水科学与技术， 2009， 博士

【摘要】 聚1,5-二氨基蒽醌（P1,5-DAAQ）是一种新型导电聚合物材料,其电化学反应过程对应着其类似聚苯胺的导电骨架的掺杂/脱掺杂过程以及蒽醌基团的得失电子过程。这两种过程在共轭体系中的同一分子单元中发生,不但使氨基蒽醌聚合物的结构得到优化,还使其具有很高的电活性,使其在能量存储和电催化等方面表现出优异的性能。电催化氧还原技术是化学修饰电极电催化领域研究的热点问题。醌类化合物修饰电极具有的明显的电催化氧还原活性,引起了电化学工作者的广泛研究。本论文中研究的氨基蒽醌聚合物修饰电极,与其它方法（如吸附、掺杂等）得到的醌类修饰电极比较,具有性质稳定、制备过程简单、活性点位浓度高等优点,而且同时具有类似聚苯胺的长链结构和蒽醌官能团的特性,为制备具有高氧还原催化活性的蒽醌修饰电极的研究提供了新的思路。本论文采用电化学阳极氧化法制备聚1,5-二氨基蒽醌（P1,5-DAAQ）修饰的Pt电极。并采用循环伏安法、计时安培法、电化学交流阻抗法等电化学检测技术,以及扫描电子显微镜、傅立叶红外光谱法等表征方法研究了P1,5-DAAQ修饰的Pt的电化学性质、稳定性,及其对氧2电子还原为过氧化氢的电催化活性,探讨了其在电Fenton技术中应用的可行性。采用循环伏安法可以使1,5-DAAQ单体在Pt电极表面发生电化学氧化聚合,形成黑色的薄层聚合物膜。聚合过程受温度的影响明显,当控制聚合反应在10℃时,可以得到最优的聚合效果。采用扫描电子显微镜、傅立叶红外光谱法以及电化学分析方法研究了P1,5-DAAQ的聚合过程。发现P1,5-DAAQ的聚合过程分为两个阶段:聚合物的成核阶段,即在聚合反应的初期,单体氧化形成聚合点位的核心;包括二维生长期和三维生长期的聚合物的生长阶段。采用电化学检测方法和傅立叶红外光谱法研究了Pt/P1,5-DAAQ电极在不同酸性溶液中的氧化还原行为和稳定性。研究发现,氧化过程与还原过程中,P1,5-DAAQ膜内离子的传输过程是不同的,且与离子的半径关系密切。H⁺的传输为非扩散控制过程;而阴离子进入和排除聚合物膜的过程则受扩散控制。并建立了用于描述此过程的模型。P1,5-DAAQ膜内水合阴离子的扩散系数符合Cl^->SO₄^2->NO₃^->PO₄^3-的关系。聚合物降解过程的研究中不但考察了P1,5-DAAQ在可逆电位范围内的降解,而且研究了P1,5-DAAQ的阳极过氧化现象。研究发现,在可逆电位区域,P1,5-DAAQ在0.5 mol/LHCl、H₂SO₄、HNO₃以及H₃PO₄中的降解速率常数分别为2.46、4.93、2.46和2.85×10^-4 s^-1。在比可逆电位更正的电位范围内,P1,5-DAAQ会发生阳极过氧化现象。过氧化过程中P1,5-DAAQ发生了不完全降解,类醌结构被破坏,π键共轭长度降低,聚合物的长链结构被破坏,同时,阴离子结合到聚合物当中。Pt/P1,5-DAAQ电极在0.1 mol/L H₂SO₄中对氧还原反应具有明显的电催化活性,在0.1 mol/L H₂SO₄中的氧还原峰电位为0.39 V,氧还原反应以2电子还原为主。循环伏安法、计时安培法和电化学交流阻抗法的研究发现Pt/P1,5-DAAQ电极的电催化氧还原活性受膜的厚度、溶液的pH值的影响明显。不同厚度的P1,5-DAAQ膜表面存在不同的氧传输过程。根据不同厚度的P1,5-DAAQ修饰的Pt电极表面的氧扩散系数、电子传输阻力、氧还原反应速率常数等数据的比较,证明尽管较厚的P1,5-DAAQ提供了更多的真实电极面积和更高的活性点位浓度,短时间内更有利于电催化氧还原反应,但较薄的P1,5-DAAQ修饰的Pt电极平整的表面形貌更有利于氧的传质,使其表现出更好的电催化氧还原性能。Pt/P1,5-DAAQ电极的电催化氧还原的活性随pH值的升高而降低。另外,随着P1,5-DAAQ的降解,其氧还原催化活性也逐渐降低。对Pt/P1,5-DAAQ电极作为氧还原阴极在电Fenton体系中的应用进行了研究。考察了其用于电催化O₂生成H₂O₂时的速率和电流效率及其影响因素。而且,此电极对Fe³⁺的还原也表现出了明显的电催化活性。并采用电化学阻抗法研究了此电极表面主要还原反应的竞争关系。当此电极作为氧还原阴极用于电Fenton反应时,可以在-0.2到0.1 V的电位范围内,pH值为2-3的酸性溶液中,实现对溴氨酸的降解脱色。并通过对溴氨酸降解动力学的分析,考察不同反应条件对此电Fenton体系氧化降解能力的影响。更多还原

【Abstract】 Poly-1,5-diaminoanthraquinone （P1,5-DAAQ） is a new conducting polymer. Its electrochemical reaction includes quinine / hydroquinone （Q/HQ） redox reactions and anions doping/undoping process which is similar to the electrochemical behavior of polyaniline （PANI）. These two electrochemical reactions happens in one polymer macromolecule, which can not only improve the structure of aminoanthraquinone polymer, but also provides a better electrochemical activity.The electrocatalysis for oxygen reduction reaction （ORR） has recived much attention in the researches on chemical modified electrode. It has been proved that surface confined quinones can greatly impove the electrocatalytic activity for ORR. Poly-aminoanthraquinone modified electrode is more stable, more easily prepared, and can provide higher surface concentration of reactive sites compared with other quinones modified electrode by adsorpsion or doping. Moreover, poly-aminoanthraquinone with the coexistence of anthraquinone fuction group and chain structure similar to PANI provides a new method for preparation of anthraquinone modified electrode with high electrocatalytic activity for ORR.P1,5-DAAQ have been synthesized by electrochemical oxidative polymerization on the Pt electrode in our research. Its electrochemical characteristics, stability, and electrocatalysis for ORR have been investigated using scan electron microscope （SEM）, Fourier transform infrared spectroscopy （FTIR）, and various electroanalytical techniques such as cyclic voltammetry （CV）, chronoamperometry （CA）, and electrochemical impedance spectroscopy （EIS）.P1,5-DAAQ was synthesized by CV on the Pt electrode which is an ultra thin, homogeneous, and dense polymer film. The electropolymerization process of 1,5-DAAQ can be strongly influenced by the temperature. As a result, the best characteristic for P1,5-DAAQ can be obtained when the electropolymerization process is controlled at 10℃. The electropolymerization process of 1,5-DAAQ has been investigated by CV, FTIR and SEM. It has been proposed that the electropolymerization consists of two phases: the deposition of P1,5-DAAQ from the oxidation of 1,5-DAAQ monomers, and the polymer growth process consist of two-dimension and three-dimension growth. The electrochemical characteristics and stability of P1,5-DAAQ has been investigated in different acidic aqueous solution by electrochemical methods and FTIR. It has been proved that ion transfers are different between oxidation and reduction processes, and are profoundly influenced by the sizes of ion radius during the redox process of P1,5-DAAQ in acid solution. The H⁺ transfer is diffusionless, while the insertion/expulsion of big aqua anions is controlled by diffusion. A model has been proposed to describe these ion transfer processes. The diffusion coefficients of aqua anions in P1,5-DAAQ are in the order of Cl^- > SO₄^2-> NO₃^-> PO₄^3-. As a result of stability research, degradation of polymer exists not only in overoxidation, but also in stable redox reaction. The degradation rates of P1,5-DAAQ at reversible potential region from -0.2 to 0.75 V obey the apparent first-order kinetic, and the degradation rate constants are 2.04, 4.93, 2.59, 3.03×10^-5 s^-1 in HC1, H₂SO₄, HNO₃, and H₃PO₄, respectively. According to FTIR and CV, the quinone-like sturcture is destroyed, accompanied with conjugation length of the polymer’sπ-bond decreased and chains in polymer broken and recombined with anions combined to the polymer, when P1,5-DAAQ is potentiodynamically overoxidized at 1.5 V.The P1,5-DAAQ modified Pt electrode has shown electrocatalytic activity for two-electron ORR with oxygen reduction peak at about 0.39 V in 0.1 M H2SO4. The effects of P1,5-DAAQ morphologies and the pH of electrolyte on the electrocatalytic behaviors of P1,5-DAAQ for ORR have been investigated using CV, CA and EIS measurements. We propose two different O₂-transport processes on electrodes modified with thin P1,5-DAAQ and thick P1,5-DAAQ. Together with the quantitative analysis with O₂-transport dynamics, electron-transfer resistance, and catalytic reaction rate during ORR, thin P1,5-DAAQ electrode performs better electrocatalysis for ORR for its plane morphology, although thick P1,5-DAAQ provides higher real surface area and more reactive sites which is beneficial for ORR within a short time. The ORR electrocatalytic activity for the Pt/P1,5-DAAQ electrode decreases with the increasing of pH of electrolyte, and the degradation of P1,5-DAAQ.A series of experiments have been carried out to investigate the application of the Pt/P1,5-DAAQ electrode in electro-Fenton system. It has been found that this electrode can electrogenerate H₂O₂ at 0.2 --0.2 V. The H₂O₂ generation rate and current efficiency and its effect factors have been investigated. Besides, this electrode has also shown electrocatalysis for Fe³⁺ reduction. When the Pt/P1,5-DAAQ electrode is used as an oxygen reduction cathode in electro-Fenton system, bromamine acid （BA） can be degradated. The competition between main reduction reactions on this electrode has been investigated by EIS. The influence of oxidative degradation ability for this electro-Fenton system has been analyzed with the degradation kinitics for BA.更多还原