质子交换膜燃料电池反极机理以及对膜电极性能衰减规律研究

Proton exchange membrane fuel cell (PEMFC) has been widely employed as electrochemical energy conversion systems in many fields due to its low operation temperature, high specific power, and diverse applications. However, its wide commercialization is hampered by three aspects: high cost, low catalyst activity, and low durability. As a key component of PEMFC, the degradation of membrane-electrode-assembly (MEA) has been considered as one of the main degradations for PEMFC. Among various degradation ways, cell reversal has been widely studied as one of the main factors that cause the degradation of MEA. To address this issue, this project will develop a simultaneous-detection setup to comprehensively investigate the cell reversal behavior when PEMFC is operated at different operation conditions. The correlation between the performance degradation and the reversal conditions will be established. Meanwhile, the in-plane current distribution will be further analyzed by a segmented cathode approach when PEMFC is under several cell-reversal conditions. Thereafter, in the postmortem analysis, the microstructure and physicochemical properties of catalyst layers will be inspected by micro-scale X-ray computed tomography, and transmission electron tomography and reconstruction technique, respectively. Hence, the intrinsic relationship between the in-plane current distribution and the electrode microstructure evolution will be established to reveal the reversal mechanism. Based on these experimental results, a numerical model of the catalytic layer will be founded, which will be utilized to propose anti-reversal prevention strategies in detail and guide the design of next-generation durable MEA for PEMFC.

质子交换膜燃料电池由于其运行温度低、比功率高和应用前景广泛，已经在诸多领域得到应用。然而其大规模应用还需要解决成本、活性和耐久性三方面的问题。作为质子交换膜燃料电池的核心——膜电极性能的衰减是现阶段耐久性研究的重点，而反极现象是引起膜电极性能衰减的重要因素之一。针对这一问题，本项目以预防反极现象为研究目标，采用双膜电极同步检测装置，系统分析质子交换膜燃料电池在不同条件下的反极现象，建立反极条件与反极现象之间的因果关系，对比研究反极现象对膜电极性能衰减规律。在此基础上，利用分区集流检测技术分析膜电极反极条件下面电流分布的不均匀性，以及通过X射线断层扫描技术和透射电镜重构技术从微纳尺度阐明催化层微观结构以及各项理化性质反极前后的演变规律，研究面电流分布与分区理化性质之间的内在关系，阐明反极形成机理。最后在实验基础上建立催化层数值模型，提出抗反极预防策略，指导高耐久性膜电极的制备。

提高质子交换膜燃料电池（PEMFC）膜电极长期稳定性是现阶段研究的重点，反极现象是PEMFC膜电极特有的现象，也是造成膜电极性能衰减的重要原因之一。本项目研究了PEMFC膜电极在不同工况下、不同催化层组分下的阳极反极现象，并利用电化学分析和先进理化表征，分析了反极工况对膜电极性能衰减和结构演变的规律。在此基础上，本项目开发了两种抗反极催化剂（负载型IrO2/NbTiO催化剂，高分散型IrOx催化剂），一种抗反极复合催化剂（Ir-Pt/C复合催化剂）以及基于催化层的抗反极策略（调控催化层Pt:Ir:C三者的比例，实现碳载体的均匀覆盖），三种手段均能延长膜电极阳极反极的时间，显著提高膜电极抗反极的能力，有利于提高膜电极的长期稳定性。通过本项目的实施，发表了7篇高水平论文，申请了2项中文发明专利。本项目合成的抗反极催化剂以及制定的抗反极策略，可以为高耐久性膜电极的设计和制造提供理论和方法指导。