Spectroscopic Approach to Electrode Dynamics

虽然传统的电化学方法为非均相氧化还原过程提供了大量的动力学和机理信息，但需要用现在可以通过原位表面分析技术提供的分子结构信息来补充这些信息。在现有的技术中，红外光谱非常适合于这项任务，因为光谱数据可以提供关于界面物种的身份和反应性的有价值的信息。在这个项目中，表面增强红外吸收光谱(SEIRAS)被用于Kretschmann ATR构型(棱镜/金属薄膜/溶液几何结构)。SEIRAS使我们能够在进行电化学测量的同时，检查时间分辨率为微秒的电化学反应。扫描隧道显微镜(STM)也被用来进一步证实SEIRAS的结果。本课题所涉及的主要内容如下：1.SEIRAS…的扩展更多的是铂族金属可用于SEIRAS的电极材料长期以来仅限于金、银和铜。我们成功地制备了铂等铂族金属的Seira活性电极。利用上述铂电极，以直接甲醇燃料电池为研究对象，对有机小分子的催化电氧化进行了广泛的研究。首次发现甲醇通过甲酸盐作为反应中间体被氧化成CO_2。分子在电化学界面上的吸附结合扫描隧道显微镜和电化学技术，研究了几种分子在单晶电极表面的吸附/脱附和重取向随外加电位的变化。Au(111)表面欠电位沉积铜层的溶解动力学通过同时测量SEIRAS和瞬时电流，可以分离出两个重叠的反应过程，并对其进行动力学分析。电极间的电子转移和吸附分子用时间分辨和电势调制的SEIRAS研究了固定在电极表面的分子的氧化还原行为。对于某些系统，可以检测到寿命非常短的中间体。较少

Although conventional electrochemical methods provide a myriad of kinetics and mechanistic information for heterogeneous redox processes, it is desirable to supplement this with the molecular structural information that can now be provided by in situ surface analytical techniques. Of the techniques available, infrared spectroscopy is well suited for this task since the spectral data can yield valuable information on the identity as well as reactivity of the interfacial species. In this project, surface-enhanced infrared absorption spectroscopy (SEIRAS) was used in the Kretschmann ATR configuration (a prism/thin metal film/solution geometry). The SEIRAS enables us to examine electrochemical reactions with time-resolutions down to microseconds simultaneously with electrochemical measurements. Scanning tunneling microscopy (STM) was also employed for further confirmation of the results obtained by SEIRAS. The main subjects dialed with in this project are as follows:1. Extension of SEIRAS … More to Pt-group metalsThe electrode materials usable for SEIRAS have long been limited only to Au, Ag, and Cu. We succeeded in preparing SEIRA-active electrodes of Pt and other Pt-group metals.2. Electro-oxidation of C1 molecules on Pt catalystsUsing the Pt electrodes mentioned above, catalytic electro-oxidation of small organic molecules was investigated extensively with direct methanol fuel cells in mind. We found for the first time than methanol is oxidized to CO_2 via formate as a reactive intermediate.3. Molecular adsorption at the electrochemical interfaceAdsorption/desorption and reorientation of several molecules on single-crystal electrode surfaces have been investigated as a function of applied potential in conjunction with STM and electrochemical techniques.4. Dynamics of the Dissolution of An Underpotentially Deposited Cu Layer on Au(111)By simultaneous SEIRAS and transient current measurements, two overlapping reaction processes could be separated and analyzed kinetically.5. Electron transfer between electrodes and adsorbed moleculesRedox behaviors of molecules immobilized at electrode surfaces were examined with time-resolved and potential-modulated SEIRAS. Very short-lived intermediates could be detected for some systems. Less