Development of Oxygen Electrode for Polymer Fuel Cell Worked under Neutral and Room Temperature Conditions

本课题的研究目的是开发中性和室温条件下工作的聚合物燃料电池氧电极。首先，采用常规方法合成了多种π共轭氧化还原聚合物。含酸性基团的聚苯胺作为自掺杂导电聚合物，由于其酸性基团的自掺杂，在较宽的pH范围内表现出优异的氧化还原活性，并可作为高分子金属配合物的配体。用电化学方法研究了聚苯胺-离子堆积双核钴卟啉配合物（PCAn-Co2 P）在修饰玻碳电极上的催化行为。利用自掺杂的聚苯胺-Co-卟啉配合物，在中性条件下（pH6.2）实现了氧的4电子还原，还原效率超过90%。在该体系中，聚（2，3-二羧基苯胺）是一种优良的电子介体。研究表明，氧的4-电子还原反应的关键过程是电子从钴向氧的转移，然后再从氧化还原聚合物向二氧代钴配合物的转移，氧化还原电位与钴卟啉（CoII/CoIII）相近的聚苯胺类聚合物配合物对氧的4-电子还原反应表现出良好的催化活性.随着聚合物与钴络合物之间电子转移过程DG的增加，催化效率急剧下降。作为实现燃料电池高效氧电极的策略，因此，聚苯胺衍生物可以作为一种导电的自掺杂聚合物电解质，其氧化还原电位与钴卟啉类似（CoII/CoIII），其中聚合物复合物中的酸性结构域即使在升高的pH下也提供稳定的催化活性。

Objective of this project is on Development of Oxygen Electrode for Polymer Fuel Cell Worked under Neutral and Room Temperature Conditions.First, various π-conjugated redox polymers were synthesized by the conventional methods. Poly aniline with acidic group as a self-doping conductive polymer shows excellent redox activity over a wide pH range due to the self-dopable acidic group and acts as a polymer ligand for macromolecular metal-complexes. The catalytic behavior of the polyaniline-ionically stacked dinuclear cobalt-porphyrin complex (PCAn-Co2P,) was studied using electrochemical techniques on the modified glassy carbon electrode. We achieved the 4-electron reduction of oxygen to water in neutral conditions (pH 6.2) with more than 90% efficiency by using the self-doped polyaniline-Co-porphyrin complex. In this system poly (2,3-dicaboxy aniline) acts as an excellent electron mediator. Our study reveals that the key process of the 4-electron reduction of oxygen is the sequential electron transfer from the redox polymer to the dioxo cobalt complex after the electron transfer proceeded from cobalt to oxygen.Polymer complexes of the polyanilines with the similar redox potential to that of cobalt porphyrine(CoII/CoIII) show a good catalytic activity for the 4-electron reduction of oxygen. Sequential electron injection into the cobalt complex takes place smoothly The catalytic efficiency drastically decreases with increase of the DG of the electron transfer process between polymer and cobalt complex.As a strategy to achieve an efficient oxygen electrode for the fuel cell, we concluded that polyaniline derivatives should be employed as a conductive self-dopable polymer electrolyte with the similar redox potential to that of cobalt porphyrin (CoII/CoIII), in which the acidic domains in the polymer complex provides a stable catalytic activity even at elevated pH.