The Emergence of Atomic-Level Structural Information for Ordered Metal-Solution Interfaces: Some Recent Contributions from In-Situ Infrared Spectroscopy and Scanning Tunneling Microscopy

The utilization of infrared reflection-absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM) to extract atomic-resolution information for ordered metal-solution interfaces in a related (and relatable) fashion to metal-ultrahigh vacuum (UHV) surfaces is illustrated by means of some recent results from our laboratory. Two specific topics are addressed. The first involves the potential-dependent properties of saturated carbon monoxide adlayers on low-index platinum and rhodium electrodes in aqueous and nonaqueous media. The central role of the surface potential in controlling the CO adlayer structure is discussed on the basis of in-situ IRAS data, especially in comparison with the properties of corresponding metal-uhv interfaces. The application of in-situ atomic-resolution STM in tandem with IRAS for elucidating real-space adsorbate structures is noted for saturated CO adlayers on Rh(111) and Rh(110) electrodes. The second topic concerns the application of in-situ STM to probe potential induced reconstruction at gold-aqueous interfaces. All three low-index gold surfaces are seen to undergo reconstruction at potentials corresponding to small negative electrode charges.