Electrochemistry at Well-Characterized Bimetallic Surfaces - Fuel Cell Catalysis: A Surface Science Approach - page 243

& CHAPTER 8
Electrochemistry at Well-Characterized
Bimetallic Surfaces
VOJISLAV R. STAMENKOVIC and NENAD M. MARKOVIC
Argonne National Laboratory, Materials Science Division, University of Chicago, Argonne, IL 60439, USA
8.1 INTRODUCTION
Interest in electrochemistry on well-defined (usually single-crystalline) surfaces has
risen steadily over the last four decades, and coincides with the development of surface
structural techniques for the microscopic-level characterization of metal single-crystal
surfaces in ultrahigh vacuum (UHV). Not surprisingly, an early emphasis was placed
on developing the UHV-based experimental strategies applicable to electrochemical
interfaces. This ex situ approach, pioneered during the 1970s by Hubbard (1998),
Yeager [Hagans et al., 1979], and in Ross (1982), provided the first successful
means of obtaining atomic-level structural information for electrochemical adsorbates
on metal single-crystal surfaces. Although such an ex situ strategy opened some new
directions in surface electrochemistry, establishing the relationship between the struc-
ture of the interface in an electrolyte and that observed in UHV was always problematic,
and had to be carefully examined on a case-by-case basis. More sophisticated micro-
scopic-level descriptions of electrochemical systems became possible in the early
1990s through the emergence of new in situ surface-sensitive probes, most notably syn-
chrotron-based surface X-ray scattering (SXS) [Ocko et al., 1990; Lucas et al., 1996;
Tidswell et al., 1993] and scanning tunneling microscopy (STM) [Bard et al., 1991;
Kolb, 1996; Itaya, 1998]. While these two techniques are markedly different in
character and exhibit contrasting strengths, both are providing information on
potential-dependent surface structures at a level of sophistication that is on a par
with (or even beyond) that obtained for surfaces in traditional (vacuum-based) surface
science [Somorjai, 1985]. Of the various systems examined, a decided emphasis has
been placed on elucidating the surface electrochemistry of bimetallic surfaces,
which play a crucial role in a number of technologically important areas, including