Study of ultramicroelectrode-based-measurement system for polymer electrolyte/electrocatalyst interface

通过制造一系列超微电极，构建了三电极体系难以应用的聚合物电解质膜/电催化剂层状结构电化学测量系统。该系统成功地使我们能够评估基于小电流诱导的小iR下降的界面电化学反应，即使在高电阻率介质中也是如此。此外，微阵列电极还揭示了电催化过程的反应机理。因此，聚合物电解质燃料电池（PEFC）的电化学测量系统应运而生。主要研究成果总结如下：首先，在玻璃毛细管的尖端制造了一个集成的超微电极，它包括工作微电极、计数微电极和参考微电极。用这种方法测定了氢和甲醇氧化的气相电化学反应。其次，通过改变水：甲醇混合物的比例，采用交叉微阵列电极测量了聚合物电解质膜的离子电导率。这对直接甲醇燃料电池（DMFC）的运行是有价值的。第三，利用交叉指状微阵列电极首次检测到传统旋转环盘电极无法记录的甲醇氧化中间体。其次，制作了多孔微电极，其尖端有一个微腔，用于测量颗粒材料的电化学性能。这样就可以对粉末形式的电催化剂进行常规评价。最后，制备了一种多孔微环电极，其尖端具有聚合物电解质/电催化剂层状结构，用于电化学评价膜电极组件（MEA）。在结论。通过设计和制造新型超微电极，聚合物电解质膜/电催化剂结构的电化学表征得到了很大的进展。

Electrochemical measurement system for polymer electrolyte membrane/electrocatalyst layered structure, where the three-electrode system was difficult to apply so far, has been constructed by creating a series of ultramicroelectrodes. The system successfully enabled us to evaluate the interfacial electrochemical reaction based on a small-current-induced small iR drop even in the high resistivity medium. In addition, microarray electrode revealed a reaction mechanism of the electrocatalytic process. Consequently, electrochemical measurement system for polymer electrolyte fuel cell (PEFC) has been developed. Main research results are summarized as follows. First, an integrated ultramicroelectrode has been fabricated which involves working, counter and reference microelectrodes at a tip of a glass capillary. By using this, the gas phase electrochemical reactions were measured for hydrogen and methanol oxidation. Second, ionic conductivity of polymer electrolyte membrane has been measured employing an interdigitated microarray electrode by changing a water:methanol mixture ratio. Which is worthwhile for an operation of direct methanol fuel cell (DMFC). Third, by utilizing the interdigitated microarray electrode, methanol oxidation intermediate, which could not recorded at a conventional rotating ring-disk electrode, has been detected for the first time. Next, a porous microelectrode has been made which has a microcavity at the tip to measure electrochemical properties of particulate materials. This allowed a conventional evaluation of electrocatalysts in a powder form. Finally, a porous microring electrode, which has polymer electrolyte/electrocatalyst layered structure at the tip, has been created for a purpose to appraise a membrane electrode assembly (MEA) electrochemically. In conclusion. By designing and fabricating novel ultramicroelectrodes, electrochemical characterization for polymer electrolyte membrane/electrocatalyst structure has been greatly progressed.