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

Some prospects for applying scaning tunneling microscopy (STM) as an i n-situ atomic-resolution probe of adlayer structure at ordered metal-s olution interfaces are considered with respect to both equilibrium and reactive adsorbate systems. Illustrative results of the former type a re presented for the potential-dependent adsorption of iodide at low-i ndex gold electrodes. The virtues of acquiring ''composite-domain'' ST M images, where the electrode potential is altered during data acquisi tion so to form or remove the adsorbed adlayer, are noted. By generati ng temporally and spatially adjacent domains featuring substrate and a dlayer images in this fashion, the registry between the former and lat ter atomic arrangements can be deduced with high precision. The suitab ility of in-situ STM for examining real-space dynamics of surface phys ical and chemical processes is illustrated for potential-induced recon struction of Au (100) and for the electrooxidative polymerization of i odide and sulfide. Some limitations as well as strengths of in-situ ST M for these purposes are briefly outlined with regard to its anticipat ed role in the development of in-situ electrochemical surface science.