频繁反极对燃料电池膜电极抗反极能力及性能影响

Effect of frequent reverse polarity on anti reverse ability and performance of membrane electrode of PEMFC

质子交换膜燃料电池中发生的反极现象严重制约了其寿命,目前国内外研究者聚焦于膜电极的一次抗反极能力,而反极事件极有可能在整个燃料电池电堆运行期间频繁发生。在单电池上模拟电堆反极的状态并对阳极添加有氧化铱催化剂的抗反极膜电极进行多次反极实验,采用一系列电化学诊断工具和扫描电镜来研究其反极行为和性能衰退情况。结果表明膜电极的抗反极时间随着经历反极次数增多而急剧缩短。在经历三次反极后,电池功率密度衰退了近50%,阳极电化学活性面积降低了63.4%,而阴极侧仅降低了5.5%,此时阳极活化极化对电池性能的影响不可忽视,电池在800 mA/cm2时内阻增加为原来的3倍。扫描电镜观察到碳载体被严重腐蚀,催化层结构坍塌,反极使得阳极催化层厚度减薄了约50%,氧化铱颗粒发生了明显团聚。该研究结果对于设计可靠、耐久的抗反极膜电极具有重要意义。

Voltage reversal severely restricts the lifespan of proton exchange membrane fuel cell.Most researchers only focus on the first reversal tolerance.However,cell reversal events would frequently occur in the lifetime of the fuel cell stack.The reverse electrode state of the stack was simulated on a single cell,and the anti reverse electrode film electrode with iridium oxide catalyst on the anode was carried out many times.A series of electrochemical diagnostic tools and scanning electron microscopy were used to study the reverse polarity behavior and performance degradation.The experimental results show that the voltage reversal time(VRT)of the RTA MEA dramatically decreased with the reversal tests.After three reversal tests,the cell power density almost declines by 50%,and the electrochemical surface area(ECSA)of the cell’s anode decreases by 63.4%,while that of cathode only reduces 5.5%.The impact of anodic activation polarization on cell performance cannot be ignored.The cell ohmic resistance 800 mA/cm2 is tripled that of beginning-of-life.We observe the serious agglomeration of IrO2 catalyst and the structural collapse of the anode catalyst layer from electron micrographs.The catalyst layer thickness reduces 50%.The results are of great importance for designing reliable and durable RTA.