【作者】 朱晓兵；

【导师】 张华民；

【作者基本信息】 中国科学院研究生院（大连化学物理研究所） ， 化学工程， 2006， 博士

【摘要】 质子交换膜燃料电池技术倚重于质子交换膜和电催化剂两种关键材料的发展。质子交换膜主要起着阳极和阴极的电子隔离和反应气的隔离作用,并且提供电解质的质子导电功能。质子交换膜位于燃料电池中的膜电极三合一（MEA）的中间位置,在燃料电池研究中愈来愈显更为至关重要的作用。复合型质子交换膜是当前的研究热点之一。本论文通过提高膜的机械强度、降低膜厚度,以提高电池性能、降低成本为目标,研究和开发燃料电池用质子交换膜。薄膜显著降低电池内阻而提高电池性能,同时薄膜降低膜材料使用量因而降低成本。通过对多孔PTFE膜进行液相介质氧化处理,改善了其浸润性,提高了离子聚合物（如Nafion或SPSU）与PTFE之间的界面相容性;合成了厚15-30μm致密的Nafion/PTFE和SPSU/PTFE增强复合质子交换膜;研究了增强复合自增湿质子交换膜（Pt-SiO₂催化剂、Nafion和PTFE复合物,简称Pt-SiO₂/NP）,膜内吸湿性的纳米级SiO₂担载Pt催化剂提高阳极的自增湿功能和降低阴极混合电位,因而提高了其电池开路电压（OCV）和电池性能,同时利于膜内的水平衡;研究了基于双磺化聚醚砜浸渍膨胀拉伸多孔PTFE的复合质子交换膜（SPSU/PTFE）。采用Pb2+染色TEM手段研究了IONOMER/PTFE类型复合膜（如Nafion/PTFE）的离子簇微相区的结构,发现膜内离子簇团的定向聚集现象,并探讨了离子簇团定向聚集与膜的质子传导机理的关联。更多还原

【Abstract】 Currently, the development of key materials, the proton exchange membranes (PEMs) and the electrocatalysts, is now considered as the impediment to the success of the PEM fuel cell technology and thus should be given high priority. The PEM, located in the central of the fuel cell, has gained a more and more central importance in fuel cell R&D. The main task of the PEM is to separate the anodic and cathodic chambers in terms of electric isolation and reactant separation, and provide the function of a proton conductive electrolyte. Composite PEMs are of much importance in fuel cell membrane fields.In this thesis, with the two targets of cost and performance in mind, also required for PEM fuel cells for transportation applications, ultrathin composite membrane based on micro-porous expanded PTFE and ionomer (such as Nafion or disulfonated poly(arylene ether sulfone) etc.) were developed and investigated. In detail, the composite membranes based on PTFE and ionomer (Nafion or SPSU), can be made ultrathin for PEMFC due to PTFE reinforcement effect. The strategy of implement of thin membrane could great contribute to the reduced areal specific resistance and voltage drop, thus leading to high cell performance. However, a key issue exists in the synthesis or fabrication process of ionomer/PTFE membranes, namely, interface compatibility between hydrophobic PTFE and hydrophilic ionomer components. The surface modification of PTFE could improve interface compatibility. These twoconsiderations promoted successful development of Ionomer/PTFE membranes with excellent fuel cell performances.To well meet current low or none humidification requirement of PEMFC, sandwich-structured self-humidifying membrane (nanometer-sized SiO2 supported Pt catalyst, Nafion and PTFE composites, donated as Pt-SiO2/NP) was fabricated, characterized and experimentally analyzed. Surprisingly, this membrane could be applied in not only low temperature PEMFC, but high temperature PEM fuel cell (operated at 120 oC, R.H. = 25%). In detail, the SiO2 supported Pt catalyst (Pt-SiO2) in both side layers of the membrane suppresses gas-crossover by chemically catalyzing mutually permeable H2 and O2 to produce H2O, which can in situ hydrate the membrane and facilitate water balance. The recombination reaction inside the membrane occurs chemically not electrochemically, since the insulation of SiO2 results in lack of electron channel, which is essential for three phase interfaces required for electrochemical reaction. The reduction in membrane thickness can facilitate water back-diffusion. In the design, the anode side layer is used for membrane self-humidification and the cathode side layer aims to decrease oxygen electrode polarization, especially at low current density, and accordingly improve the cell OCV. Hydrophilic nanometer-sized SiO2 inside the membrane is expected to adsorb water at low current density, and to release water at high current density to satisfy the electro-osmotic drag requirement. The fuel cells performance data employing above three membranes (such as Nafion/PTFE, Pt-SiO2/NP and SPSU/PTFE) were far superior than virtually all existing literature data.Moreover, interestingly, the phenomenon of ionic cluster aggregation aligned along PTFE nano-rods and nodes in ionomer/PTFE membrane was observed and investigated. Furthermore, the behavior of ionic cluster aggregation was correlatedwith proton conduction mechanism and fuel cell performance.更多还原