Atomic and molecular scale structural analysis of electrode/electrolyte interfaces

本研究项目的目的是在原子和分子尺度上表征电化学界面，以便更深入地了解界面和在那里发生的反应。本实验室开发的表面增强红外吸收光谱（SEIRAS）和扫描隧道显微镜（STM）结合传统电化学技术对界面进行了表征。特别关注了界面和反应的动态行为。一种新的红外光谱技术，能够监测非常事实的电极动力学和动力学已开发为此目的。所得结果总结如下：(1)双层结构。长期以来，人们一直认为电化学界面上的水分子与体中的氢键网络分离，并随着外加电位重新定向。这一假设首次通过SEIRAS得到验证。推导出的取向与经典模型的取向不同，与最近的分子动力学模拟结果一致。我们还发现，支持阴离子的共吸附在很大程度上改变了双层结构。(2)电极动力学。我们首次成功地进行了红外和电化学同时测量，这使得对电极动力学的详细研究成为可能。研究了双层结构的变化、电极与吸附分子之间的电荷转移以及几种反应。(3)分子在界面处的吸附和解吸。测定了一些分子在金单晶电极上的附加结构。发现了一些分子通过吸附、层内二维相变、物理吸附-化学吸附转变和电位依赖性重定向等方式发生的分子结构变化。(4)修饰电极结构与功能的相关性。采用SEIRAS法测定了芳香硫醇自组装单层膜在金电极上的表面pKa值。研究发现，SAMs的酸碱性质对修饰电极的功能有很大的影响，如促进电极与细胞色素c之间的非均相电子转移的活性

The aim of this research project was to characterize the electrochemical interface at atomic and molecular scales in order to get deeper insight into the interface and reactions take place there. Surface-enhanced infrared absorption spectroscopy (SEIRAS) developed in our laboratory and scanning tunneling microscopy (STM) coupled with conventional electrochemical techniques were used to characterize the interface. Special attention was focused to dynamic behavior of the interface and reactions. A novel infrared spectroscopy technique that enables monitoring very fact electrode dynamics and kinetic have been developed for this purpose. The results obtained are summarized as follows :(1) Double-layer structure. It has long been assumed that water molecules at the electrochemical interface are isolated from the hydrogen-bonded network in the bulk and reorient with applied potential. This assumption was verified for the first time by using SEIRAS.The orientations deduced are different from … More those assumed in classical models and in accord with recent molecular dynamics simulations. We also found that the double-layer structure is largely changed by the coadsorption of supporting anions.(2)Electrode dynamics. We have succeeded for the first time in infrared and electrochemical simultaneous measurements, which enabled detailed investigation of electrode dynamics. Change in double-layer structure, charge-transfer between the electrode and adsorbed molecules, and several reactions were investigated.(3) Adsorption and desorption of molecules at the interface. Adstructures of a number of molecules on gold single-crystal electrodes were determined. The change in molecular structure by adsorption, two-dimensional phase transition in adlayers, physisorption-chemisorption transition, and potential-dependent reorientation were found for several molecules.(4) Correlation between the structure and functions of rnodified electrodes. Surface pKa values of self-assembled monolayers (SAMs) of aromatic thiols on gold electrodes were determined by SEIRAS.The acid-base property of SAMs was found to greatly influence the functions of the modified electrodes, such as the promotion activity toward heterogeneous electron-transfer between the electrode and cytochrome c. Less