PROBING ELECTROCHEMICAL ADSORBATE STRUCTURE AND REACTIONS WITH INSITU ATOMIC-RESOLUTION SCANNING MICROSCOPY - SOME PROGRESS AND PROSPECTS

Some prospects for applying scaning tunneling microscopy (STM) as an in-situ atomic-resolution probe of adlayer structure at ordered metal-solution interfaces are considered with respect to both equilibrium and reactive adsorbate systems. Illustrative results of the former type are presented for the potential-dependent adsorption of iodide at low-index gold electrodes. The virtues of acquiring ''composite-domain'' STM images, where the electrode potential is altered during data acquisition so to form or remove the adsorbed adlayer, are noted. By generating temporally and spatially adjacent domains featuring substrate and adlayer images in this fashion, the registry between the former and latter atomic arrangements can be deduced with high precision. The suitability of in-situ STM for examining real-space dynamics of surface physical and chemical processes is illustrated for potential-induced reconstruction of Au (100) and for the electrooxidative polymerization of iodide and sulfide. Some limitations as well as strengths of in-situ STM for these purposes are briefly outlined with regard to its anticipated role in the development of in-situ electrochemical surface science.