The application of the scanning tunneling microscope (STM) and the atomic force microscope (AFM) to electrochemical problems over the past seven years has greatly enlivened electrochemical surface science. The salient feature of these techniques is their ability to obtain real-space images of electrode surfaces with atomic resolution. The facility of obtaining this kind of direct structural information has both confirmed previously held ideas and provided new directions in the study of electrode surfaces. The direct structural information now available has also moved the entire field forward at a considerable pace. As seen in this volume, systems studied include those involving deposition, corrosion, monolayers, catalysis, and surface structural transformations. These systems are central to the core of electrochemical science and the scanning probe work is thus of the highest importance.

While the high real-space resolution and the ability to operate on surfaces under potential control in redox-active solutions are strengths of the scanning probe methods, there are also a number of drawbacks. The probe microscopies do not provide any discrimination between different chemical species present on the surface. To be sure, the STM can certainly distinguish between conducting, insulating, and semiconductor surfaces and the AFM can distinguish between soft and hard specimens. However, they provide no information about the specific chemical identity of the features observed. This lack should be contrasted to the plethora of chemical information available from such techniques as vibrational spectroscopy or potential-step chronocoulometry, which lack-the fine spatial resolution. The scanning probe methods also lack the very high resolution available from surface x-ray scattering, but this technique requires access to a synchrotron light source, is somewhat insensitive to defects, and appears to work best on high-atomic-weight systems. Therefore, to address electrochemical systems most appropriately, a combination of techniques should be utilized.

In the early days of in-situ scanning probe microscopy (SPM) work, results were hard won and often of poor quality. As practical knowledge has accumulated in the community, this difficulty has lessened, and the large number of groups represented in this volume is only one indication of the popularity and efficacy of the techniques. In what follows, we describe some of the research areas in the Gewirth group, and indicate what we feel are directions for the future.

0 0

Post a comment