Our data show that the pathology of

我们的数据表明，PEM燃料电池动力学的病理学随着时间的流逝逐渐变化。不幸的是，现有的实验设备不允许在运行期间直接观察膜以及膜-电极界面的机械，化学和电学性质。膜的机械性能和膜-电极界面都将受到老化的影响。随时间和温度范围发生振荡<br>并且在其上发生振荡的水含量表明，膜可能会由于老化而变得“更软”（即，膜的表现就好像由于老化而变得更具弹性）。5000小时运行后，相同负载电阻的电池电压和电池电流均随时间降低。在运行5000至10,000小时之间，开路电压也从0.91降至0.25V大幅降低。在扩展操作期间，我们还观察到我们不再需要关闭质量平衡。从阳极和阴极流出的水远远多于<br>对应于燃料电池电流。例如，图8中的数据表明，阳极和阴极流出物中除去的水几乎是燃料电池电流形成的水的四倍。这表明老化会增加膜的渗透性，从而允许更大的反应物穿越（分子氢和氧穿过膜，在膜中它们几乎立即在Pt催化剂上反应形成额外的水）。膜渗透性的提高可解释开路电压降低和质量平衡损失

Our data show that the pathology of the PEM fuel cell dynamics gradually changes with time on-stream. Unfortunately, the existing experimental apparatus does not permit direct observations of the mechanical, chemical and electrical properties of the membrane and the membrane–electrode interface over the time periods of operation. Both the membrane’s mechanical properties and the membrane–electrode interface are expected to experience the effects of aging. The onset of oscillations with time and the range of temperature<br>and water content over which the oscillations occur suggest that the membrane possibly becomes “softer” due to aging (i.e., the membrane behaves as if it were more elastic due to aging). Both the cell voltage and cell current for the same load resistance decreased with time after 5000 h of operation. The open circuit voltage also decreased substantially, from 0.91 to 0.25V, between 5000 and 10,000 h of operation. During the extended operation we also observed that we no longer had closure on the mass balances. There was substantially more water in the effluents from the anode and cathode than<br>corresponded to the fuel cell current. For example, the data in Fig. 8 indicate that the water removed in the anode and cathode effluents was nearly four times the water formed by the fuel cell current. This suggests that aging leads to increased membrane permeability allowing greater cross-over of the reactants (molecular hydrogen and oxygen pass through the membrane where they react on the Pt catalyst almost instantaneously to form additional water). The increased membrane permeability can account for both the decreased open circuit voltage and the loss of mass balance

我们的数据表明，质子交换膜燃料电池动力学的病理变化是随着时间的推移而逐渐变化的。不幸的是，现有的实验装置不允许在操作期间直接观察膜和膜-电极界面的机械、化学和电学性质。膜的机械性能和膜-电极界面都会受到老化的影响。随时间和温度范围振荡的开始<br>振荡发生时的含水量表明，由于老化，薄膜可能变得“柔软”（即，由于老化，薄膜表现得更具弹性）。运行5000h后，相同负载电阻的电池电压和电池电流均随时间而降低。在运行5000至10000小时期间，开路电压也大幅降低，从0.91降至0.25V。在延长操作期间，我们还观察到，我们不再关闭质量平衡。阳极和阴极排出的废水中的水比<br>对应于燃料电池电流。例如，图8中的数据表明，阳极和阴极流出物中去除的水几乎是燃料电池电流形成的水的四倍。这表明，老化导致膜的渗透性增加，允许反应物发生更大的交叉（分子氢和氧通过膜，在膜上它们几乎瞬间在铂催化剂上反应形成额外的水）。膜透性的增加可以解释开路电压的降低和质量平衡的损失