Percolation Theory for Gas Electrode of Fuel Cells

为了将统计渗滤理论应用于燃料电池气体电极，去年采用由防湿颗粒和湿敏感颗粒组成的模型催化剂层进行了渗滤实验。本年度采用磷酸燃料电池的真催化剂层进行酸渗透试验。研究发现，在酸填充量低于30%的情况下，酸可以在短时间内穿透真实的催化剂层，并且在统计上酸可以以分散点的形式存在。结果表明，如果湿敏催化剂连接和连接，则不会出现酸不动临界点。利用从长期运行的磷酸燃料电池中收集的实际碳衬底，研究了酸沿电极表面的转移。由于进、退两种润湿接触角差异的影响，尽管酸的填充水平分布差异很大，但酸仍停止了移动。当使用新的防潮基材时，这种现象显着出现。随着灌酸量的增加，酸能快速移动，但当灌酸量低于30%时，酸不能移动。这一现象得到了渗流理论估计结果的支持。这些实验和理论结果对提高磷酸燃料电池的可靠性和寿命具有重要意义。

In order to apply the statistical percolation theory to a gas electrode of fuel cells, model catalyst layers composed of wet-proofed particles and wet-susceptible particles were used for percolation experiments last year. The real catalyst layer of phosphoric acid fuel cells was used for acid percolation tests in this year.It was found that the acid could penetrate through the real catalyst layer within a short hour under acid fill level of lower than 30% in which acid could exist statistically as dispersed spots. It showed that the acid immovable critical point did not appear if the wet-susceptible catalysts were connected and linked.Acid transfer along the electrode surface was investigated using actual carbon substrates collected from the long operated phosphoric acid fuel cell. Due to the effect of the difference between progressive and drawing back wetting contact angle, acid stopped to move in spite of the large difference of the acid fill level distribution. This phenomena appeared remarkably when a new wet-proofed substrates were used.The acid could move quickly with the increase of acid fill level, but was immovable when the acid fill level became lower than 30%. This phenomena is supported by our estimated results of the percolation theory. These experimental and theoretical results can be useful for improving the reliability and the life of phosphoric acid fuel cell.