Fundamental Studies on Ionic Liquids and Ion Gels for Functional Materials

本研究旨在了解离子液体和离子凝胶的基本性质，并为其作为新材料的功能化提出新概念。主要研究方向为：(1)离子液体和离子凝胶的离子动力学和“离子性”；(2)非湿润条件下热稳定的质子导电离子液体和离子凝胶的开发及其在燃料电池中的应用；(3)电子传输离子液体和离子凝胶及其在染料敏化太阳能电池中的应用。通过离子电导率测量和脉冲梯度自旋回波核磁共振，系统地探索了普通离子液体中的动力学（pgse-NMR）测量，并在此基础上提出了离子液体的“离子性”。离子性对应于离子液体的自解离程度，并与阳离子的路易斯酸度和阴离子的路易斯碱度密切相关。研究表明，离子液体的离子性很低，大于1，表明形成了离子团簇。对于质子导电离子液体，本研究首次清晰地证明了离子液体中通过氢键网络形成的grotthuss型质子转移的存在，大大提高了质子的扩散率和质子转移数。本研究还发现离子液体与Pt的界面处发生了氢氧化和氧还原，为质子导电离子液体作为燃料电池的电解质在非湿润和中温条件下的应用开辟了可能。通过对70多种质子导电离子液体的研究，发现三氟甲磺酸二乙基甲基铵作为燃料电池电解质具有高质子导电性、高热稳定性和界面易发生电化学反应等优异性能。此外，离子液体中的多碘离子通过电子自交换反应传递电子，有趣的是，这只在离子液体中观察到，而在分子液体中没有。含有多碘离子的离子液体已被用于染料敏化太阳能电池，与使用分子溶剂的太阳能电池相比，其长期稳定性大大提高，同时又不损失光电子转换效率。纳米颗粒的加入可使离子液体电解质凝固，加速电荷输运速率。少

This study has aimed at understanding fundamental properties of ionic liquids and ion gels and at making new concept for their functionalization as new materials. Efforts have been focused on(1)Ion dynamics and "ionicity" of ionic liquids and ion gels(2)Development of thermally stable proton-conducting ionic liquids and ion gels under non-humid conditions and their application to fuel cells at > 1000C(3)Electron transporting ionic liquids and ion gels and their application to dye-sensitized solar cellsIon dynamics in common ionic liquids has been systematically explored by means of ionic conductivity measurements and pulsed-gradient spin echo NMR (pgse-NMR) measurements, and "ionicity" of the ionic liquids was proposed based on the both measurements. The ionicity corresponds to the self-dissociation degree of the ionic liquids and was found to closely correlate with Lewis acidity of the cations and Lewis basicity of the anions. It has been revealed by this study that the ionicity is lo … More wer than unity for the ionic liquids, indicating the formation of ionic clusters. Regarding to proton conducting ionic liquids, the existence of Grotthuss-type proton transfer through the hydrogen-bonding network formed in the ionic liquids was clearly demonstrated in this study for the first time, which greatly enhances the proton diffusivity and the proton transference number. Also it was discovered in this study that hydrogen oxidation and oxygen reduction occurs at the interface between the ionic liquids and Pt, which opens up the possible application of the proton conducting ionic liquids as electrolyte of fuel cells under non-humid and medium temperature operation. Thorough the investigation of more than 70 proton-conducting ionic liquids, diethylmethylammonium trifluoromethanesulfonate was found to exhibit excellent properties as fuel cell electrolyte in terms of high proton conductivity, high thermal stability, and facile electrochemical reactions at the interface. Furthermore, polyiodide ions in ionic liquids transport electron through electron self-exchange reactions, quite interestingly which is only observed in ionic liquids and not in molecular liquids. The ionic liquids containing polyiodide ions have been utilized in dye-sensitized solar cells, long-term stability of which is greatly enhanced, compared with solar cells using molecular solvents, without losing the photo-electron conversion efficiency. The ionic liquid electrolytes can be solidified by the addition of nanoparticle with the acceleration of the charge transport rate. Less