Spectroscopic Approach to Electrode Dynamics

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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