【作者】 王志涛；

【导师】 王宇新；

【作者基本信息】 天津大学 ， 化学工程， 2009， 博士

【摘要】 膜电极组件(MEA)是聚合物膜燃料电池(PEMFC)的核心部件,对聚合物膜燃料电池的性能起到关键作用。在目前PEMFC电极技术中,催化层中的催化剂、电解质和孔隙均是无序分布的,而结构无序的催化层既导致了催化剂利用率低,又造成了反应物、电子和质子传递路径长、阻力大等弊端。因此改善电极结构,开发高性能的膜电极是PEMFC研究的重要课题。本文提出通过施加电场的方式辅助制备有取向结构的PEMFC电极,从而提高垂直方向的电子和质子通道的连通性,并提高催化剂利用率。采用由微米级全极化颗粒、电解质聚合物和溶剂组成的催化剂浆料模拟体系,用高倍光学显微镜直观观察全极化颗粒在电场下的运动和取向行为。从全极化颗粒取向行为的变化,外推真实催化层中取向的形成过程。在电极催化层的制备过程中施加电场,利用电场作用制备具有取向结构的电极催化层。考察电场和催化层主要参数对电极结构取向的影响。表征催化层结构,测量其电化学性能,并且进行进一步的燃料电池实验。结果表明,电场辅助制备的电极具有较小的欧姆电阻和反应电阻,更大的电极活性面积,以及更佳的电池放电性能。近年来,人们开始积极开发以小分子碳质化合物为燃料的聚合物膜燃料电池。但不同研究者采用的实验条件不一致,使结果的可比性差,同时也缺乏高温碳质化合物燃料电池性能方面的相关研究。在本研究中,我们以Nafion?115膜作为电解质膜制备膜电极,在较高的阳极燃料和阴极氧气进料压力下,分别考察了以乙醇、甲酸、二甲醚和乙二醇为燃料的燃料电池在高温条件下(100~160℃)的放电性能,并与直接甲醇燃料电池(DMFC)进行了比较。实验表明,相比于其余四种燃料,直接甲醇燃料电池的功率密度在所考察的温度下均最大,而直接二甲醚燃料电池的开路电压则最高。使用本课题组研发的改性磺化聚芳醚酮膜作为电解质膜制备膜电极,考察了甲醇低温液态进料和高温气态进料两种情况下的燃料电池性能,并测试了以甲酸、乙二醇、异丙醇和二甲醚为燃料时的相关电池性能。实验表明,30PES/SPEEK共混膜在DMFC及直接甲酸、乙二醇、异丙醇及二甲醚燃料电池中的性能与Nafion?115膜相当,甚至更好。更多还原

【Abstract】 Membrane electrode assembly （MEA） is one of the key components of a PEMFC. The catalyst layer of the MEA is generally composed of three phases, namely a catalyst electronic conductive phase, a polyelectrolyte ionic conductive phase, and a void pores phase. These three phases are usually distributed randomly. The disordered microstructure of the catalyst layer results in the lower utilization of catalyst and the higher charge- and mass-transfer resistance. Therefore, improving the performance of PEM fuel cells by optimizing the microstructure of the MEA has been very important. In this study, electric field assisted fabrication of membrane electrode assemblies （MEAs） for fuel cells is proposed, with the aim of improving the electronic and ionic connections in the catalyst layers and increasing the efficiency of catalyst utilization.We studied the effect of an electric field on the orientation of the polarizable particles dispersed in the simulated system of the catalyst ink.Anodic and cathodic electrodes have been prepared by the perpendicular application of an electric field to the catalyst ink spread on the surface of a gas diffusion layer （GDL） while the ink is drying. The thus prepared electrodes were hot-pressed onto a Nafion membrane to form the MEAs. The performance of the electric field-treated MEAs （E-MEA） thus prepared was compared with that of common MEAs （C-MEA） without electric field treatment in a single-cell DMFC. The E-MEAs, as well as single electrodes, were also characterized by EIS, CV, and SEM methods in order to determine the changes in the E-MEAs resulting from electric field treatment. Direct methanol fuel cells （DMFCs） with the E-MEAs showed a substantial improvement in performance as compared with C-MEAs. Under the same operating conditions, the maximum power density of a DMFC was increased from 42.3 to 60.0 mW·cm^-2 when a C-MEA was replaced by an E-MEA treated with a 5000 V·cm^-1 and 0.1 Hz ac electric field. Based on cyclic voltammetry （CV） data, it has been shown that Pt utilization in the cathode reaches a maximum of 62% for the E-MEA, as opposed to 37% for the C-MEA.In recent years, direct carbonaceous compound polymer electrolyte membrane fuel cells have been developed rapidly. However, the comparability of the research results of different researchers is poor because of the different experimental conditions, and the research of the performance of the high-temperture carbonaceous compound polymer electrolyte membrane fuel cells is lacking. In this paper, we investigated the performance of the high-temperture polymer electrolyte membrane fuel cells with the MEAs prepared by Nafion?115 membrane, using ethanol, formic acid, dimethy and ethylene glycol as fuels under the higher operating pressures of the anode and the cathode, and compared with the performance of the direct methanol fuel cell operating under the same conditions. The experimental results showed that the direct methanol fuel cell presented a higher peak power density, whereas the direct dimethy fuel cell showed a higher open-circuit voltage.In addition, we prepared the MEAs with the modified sulfonated poly （aryl ether ketone） proton exchange membranes fabricated by us, and investigated the performance of the liquid-feed and vapor-feed direct methanol fuel cells and the carbonaceous compound polymer electrolyte membrane fuel cells using formic acid, ethylene glycol, isopropanol and dimethy as fuels. Single cell performance experiment indicated that the 30wt% PES/SPEEK （DS=68.3%） membrane is a competitive substitute as a proton exchange membrane for the direct carbonaceous compound polymer electrolyte membrane fuel cells.更多还原