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

本课题的目的是研制用于中性和室温条件下工作的聚合物燃料电池的氧电极。首先，采用常规方法合成了各种π共轭氧化还原聚合物。具有酸性基团的聚苯胺作为自掺杂导电聚合物，由于具有自掺杂的酸性基团，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聚合物配体。利用电化学技术研究了聚苯胺-离子堆叠双核钴卟啉配合物（PCAn-Co2P）在改性玻碳电极上的催化行为。我们利用自掺杂的聚苯胺-共卟啉配合物，在中性条件下（pH 6.2）以90%以上的效率实现了氧的4电子还原成水。在该体系中，聚（2,3-二羧基苯胺）作为一种优良的电子介质。我们的研究表明，氧的4电子还原的关键过程是从钴到氧的电子转移之后，从氧化还原聚合物到二氧钴配合物的顺序电子转移。与卟啉钴具有相似氧化还原电位的聚苯胺聚合物配合物（CoII/CoIII）对氧的4电子还原具有良好的催化活性。随着聚合物与钴配合物之间电子传递过程DG的增加，催化效率急剧降低。作为实现燃料电池高效氧电极的策略，我们得出结论，聚苯胺衍生物应作为导电自掺杂聚合物电解质，具有与卟啉钴（CoII/CoIII）相似的氧化还原电位，其中聚合物复合物中的酸性结构域即使在升高的pH下也能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.