Spatial and Temporal Behavior in Proton Exchange Membrane Fuel Cells

摘要--Nguyen-9910923质子交换膜(PEM)燃料电池系统如果性能和效率得到提高，有望取代车用内燃机。在质子交换膜燃料电池的性能控制部件中，膜和阴极是影响最大的两个部件。膜的电导率与其水合状态成正比，决定了能通过电池的电流大小。阴极处的氧还原速率是限制步骤，它决定了可以产生多少电流。在运行过程中，质子迁移效应导致水分子从阳极移动到阴极，导致阳极侧的膜脱水和阴极处的电极泛滥。膜脱水和电极泛洪问题是局部性的，导致电流分布不均匀，导致膜上局部热点和应力，可能导致电池失效。将建立分段的PEM燃料电池来检测和识别控制电流分布和时空电流密度行为的根本原因的运行条件和变量。该电池将用于识别导致电流分布不均匀的操作条件、电极特性和流场设计，以及PEM燃料电池的一般时空行为。研究结果将用于确定最佳运行条件，并开发电极和流场设计，从而提高PEM燃料电池的效率和性能。

Abstract - Nguyen - 9910923The proton exchange membrane (PEM) fuel cell system is a possible replacement for the internal combustion engine in vehicles if its performance and efficiency is improved. Of the performance controlling components in the PEM fuel cell, the membrane and the cathode are the two most influential components. The conductivity of the membrane, which is directly proportional to its hydration state, determines how much current can be passed through the cell. The oxygen reduction rate at the cathode is the limiting step and determines how much current can be generated. During operation, the effect of proton migration causes water molecules to move from the anode to the cathode resulting in membrane dehydration at the anode side and electrode flooding at the cathode. The membrane dehydration and electrode flooding problems are localized, resulting in nonuniform current distribution and result in localized hot spots and stress on the membrane that could lead to cell failure.A segmented PEM fuel cell will be built to detect and identify operating conditions and variables that control the current distribution and the root causes of spatiotemporal current density behavior. The cell will be used to identify operating conditions, electrode characteristics and flow field designs that lead to nonuniform current distribution and the general spatiotemporal behavior of PEM fuel cells. The results will be used to determine optimal operating conditions and to develop electrode and flow field designs that will result in higher efficiency and performance PEM fuel cells.