The origin of this asymmetry lies i

这种不对称性的根源在于在PEM燃料电池的阴极处形成水，该水不断地使阴极保持在足够的水合状态。由于水也<br>通过电渗透阻力从阳极到达阳极，并且水从膜上解吸以通过阴极GDL去除是一个固有的缓慢过程，水倾向于在膜和CL之间的界面附近的阴极区域积聚。通过反向扩散，甚至是压力驱动的渗透，阴极区域的高水含量便会成为浓度屏障，以防止电渗透阻力进一步从阳极进入水。这样，由于入口阳极加湿而导致的任何进入的水将趋于通过电渗透阻力和反扩散的反作用而在膜内循环和封闭，这归因于阴极处高水浓度和压力的阻止作用。驱动的渗透。反向扩散过程进一步有助于分配水<br>这种作用在整个膜上更均匀，这是文献中众所周知的机制，可降低整个膜的电阻率。由于要在<br>膜内循环的水量主要由入口阳极加湿所传入的水决定，因此膜的电阻率以及欧姆超电势变得非常容易受到阳极入口相对湿度变化的影响。因此，对于图4中的每个矩阵元素，完全湿润的阳极始终会产生最小的欧姆超电势，从而产生最大的可传递功率密度。这由图6中的水含量和欧姆超电势图支持

这种不对称的起源在于PEM燃料电池阴极处水的形成，该阴极不断将阴极保持在适当的水分状态。因为水也<br>通过电渗透阻力从阳极到达，从膜中去除水，通过阴极GDL去除是一个固有的缓慢过程，水往往积聚在膜和CL接口附近的阴极区域。通过反扩散甚至压力驱动的渗透，阴极区域的高含水量充当浓度屏障，防止电渗透阻力从节点进一步流入水。这样，任何因入口阳极加湿而流入的水，在阴极高水浓度的阻断作用和压力驱动渗透的帮助下，往往会通过电渗透阻力和背部扩散的抵消作用在膜内循环和限制。反扩散过程进一步有助于分配水<br>更均匀的膜，一种从文献中众所周知的机制，并降低整体膜的电阻性。由于要在内循环的水量<br>膜主要由入口阳极加湿的入水决定，膜的电阻性，因此，欧米茄超可能，极易受阳极入口相对湿度变化的影响。因此，对于Fig.4中每个矩阵的元素，完全加湿的节点总是产生最小的欧米茄超可能，因此产生最大的可交付功率密度。这得到了图 6 中含水量图和哦米奇超潜力图的支持

The origin of this asymmetry lies in the formation of water at the cathode of PEM fuel cell that constantly maintains the cathode at an adequately hydrated state. Since water alsoarrives from anode by electro-osmotic drag, and water desorption from membrane for removal through cathode GDL is an inherently slow process, water tends to accumulate at the cathode region near the interface between membrane and CL. By means of back-diffusion and even pressure-driven permeation, the high water content at the cathode region then acts as a concentration barrier to prevent further incoming water from anode by electro-osmotic drag. In this way, any incoming water due to inlet anode humidification will tend to be circulated and confined within the membrane by the counteracting actions of electro-osmotic drag and back diffusion, aided by the blocking action of the high water concentration at cathode, and pressure-driven permeation. The back-diffusion process further helps to distribute watermore evenly across the membrane, a mechanism that is well known from the literature, and lower the overall membrane’s resistivity. Since the amount of water to be circulated withinthe membrane is mainly determined by the incoming water from inlet anode humidification, the membrane’s resistivity, and hence ohmic overpotential, becomes highly susceptible to the variation of inlet relative humidity at anode. Therefore, for each matrix’s element in Fig.4, fully humidified anode always gives rise to the smallest ohmic overpotential and hence the maximum deliverable power density. This is supported by the plots of water content and ohmic overpotential in Fig. 6<br>