Surface electrochemistry

1 Department of Chemical and Biomolecular Engineering, Cullen College of Engineering, University of Houston, Houston, TX 77204, USA 2Stanford Synchrotron Radiation Laboratory, Post Office Box 20450, Stanford, CA 94309, USA 

In the last 40 years, modern surface science techniques have been developed to provide information about solid surfaces and interfaces on the atomic or molecular level [1]. Surface Science studies have revealed adsorption sites, electronic structure 

Inspired by these Surface Science studies at the gas-solid interface, the field of electrochemical Surface Science ( Surface Electrochemistry ) has developed similar conceptual and experimental approaches to characterize electrochemical surface processes on the molecular level. Single-crystal electrode surfaces inside liquid electrolytes provide electrochemical interfaces of well-controlled structure and composition [2-9]. In addition, novel in situ surface characterization techniques, such as optical spectroscopies, X-ray scattering, and local probe imaging techniques, have become available and helped to understand electrochemical interfaces at the atomic or molecular level [10-18]. Today, Surface electrochemistry represents an important field of research that has recognized the study of chemical bonding at electrochemical interfaces as the basis for an understanding of structure-reactivity relationships and mechanistic reaction pathways. 

In this chapter, we will first discuss thermodynamic and kinetic concepts of electrified interfaces and point out some distinct features of electrochemical reaction processes. Subsequently, we will relate these concepts to chemical bonding of adsorbates on electrode surfaces. Finally, a discussion of the surface electrocatalytic mechanism of some important technological electrochemical reactions will highlight the importance of understanding chemical bonding at electrified surfaces. 

For electrochemical reactions to occur at an electrode/electrolyte interface, equal amount of electrical charges need to enter and leave the electrolyte solution. This implies that electrochemical reactions always require two (or a multiple of two) interfaces at which charge transfer occurs. 

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As on previous occasions, the reader is reminded that no very extensive coverage of the literature is possible in a textbook such as this one and that the emphasis is primarily on principles and their illustration. Several monographs are available for more detailed information (see General References). Useful reviews are on future directions and anunonia synthesis [2], surface analysis [3], surface mechanisms [4], dynamics of surface reactions [5], single-crystal versus actual catalysts [6], oscillatory kinetics [7], fractals [8], surface electrochemistry [9], particle size effects [10], and supported metals [11, 12]. 

One of the main uses of these wet cells is to investigate surface electrochemistry [94, 95]. In these experiments, a single-crystal surface is prepared by UFIV teclmiqiies and then transferred into an electrochemical cell. An electrochemical reaction is then run and characterized using cyclic voltaimnetry, with the sample itself being one of the electrodes. In order to be sure that the electrochemical measurements all involved the same crystal face, for some experiments a single-crystal cube was actually oriented and polished on all six sides Following surface modification by electrochemistry, the sample is returned to UFIV for... 

Bockris J O M and Khan S U 1993 Surface Electrochemistry (New York Plenum)... 

The surface electrochemistry of Pt single-crystal electrodes has been exhaustively studied using cyclic voltammetry.100 186 188 197 209 412 753-756,771,-773,779-788,794-796 qq g technique has been proved to be highly... 

X. O M. Bockris and S. U. M. Khan, Surface Electrochemistry. A Molecular Level Approach, Plenum Press, New York, 1993. 

Wiekowski, A. In Situ Surface Electrochemistry Radioactive Labeling 21... 

E.M. Stuve, A. Krasnopoler, and D.E. Sauer, Relating the in-situ, ex-situ, and non-situ environments in surface electrochemistry, Surf. Sci. 335, 177-185 (1995). 

FIGURE 27.39 Schematic diagram of a surface electrochemistry apparatus, showing UHV system, transfer manipulators, and interlocks. 

Kohei Uosaki received his B.Eng. and M.Eng. degrees from Osaka University and his Ph.D. in Physical Chemistry from flinders University of South Australia. He vas a Research Chemist at Mitsubishi Petrochemical Co. Ltd. from 1971 to 1978 and a Research Officer at Inorganic Chemistry Laboratory, Oxford University, U.K. bet veen 1978 and 1980 before joining Hokkaido University in 1980 as Assistant Professor in the Department of Chemistry. He vas promoted to Associate Professor in 1981 and Professor in 1990. He is also a Principal Investigator of International Center for Materials Nanoarchitectonics (MANA) Satellite, National Institute for Materials Science (NIMS) since 2008. His scientific interests include photoelectrochemistry of semiconductor electrodes, surface electrochemistry of single crystalline metal electrodes, electrocatalysis, modification of solid surfaces by molecular layers, and non-linear optical spectroscopy at interfaces. 

Bhzanac BB, Arenz M, Ross PN, Markovic NM. 2004b. Surface electrochemistry of CO on reconstructed gold single crystal surfaces studied by infrared reflection absorption spectroscopy and rotating disk electrode. J Am Chem Soc 126 10130-10141. 

Markovic NM, Lucas CA, Rodes A, Stamenkovic V, Ross PN. 2002. Surface electrochemistry of CO on Pt(lll) Anion effects. Surf Sci 499 L149-L158. 

Palaikis L, Zurawski D, Hourani M, Wieckowski A. 1988. Surface electrochemistry of carbon monoxide adsorbed from electrolytic solutions at single crystal surfaces of Pt(lll) and Pt(lOO). Surf Sci 199 183-198. 

Mayrhofer KJJ, Arenz M, Bhzanac BB, Stamenkovic VR, Ross PN, Markovic NM. 2005a. CO surface electrochemistry on Pt-nanoparticles A selective review. Electrochim Acta 50 5144-5154. 

The methodology of surface electrochemistry is at present sufficiently broad to perform molecular-level research as required by the standards of modern surface science (1). While ultra-high vacuum electron, atom, and ion spectroscopies connect electrochemistry and the state-of-the-art gas-phase surface science most directly (1-11), their application is appropriate for systems which can be transferred from solution to the vacuum environment without desorption or rearrangement. That this usually occurs has been verified by several groups (see ref. 11 for the recent discussion of this issue). However, for the characterization of weakly interacting interfacial species, the vacuum methods may not be able to provide information directly relevant to the surface composition of electrodes in contact with the electrolyte phase. In such a case, in situ methods are preferred. Such techniques are also unique for the nonelectro-chemical characterization of interfacial kinetics and for the measurements of surface concentrations of reagents involved in... 

We have recently modified U7) one of the several radiochemical methods (U5) which have been used for surface electrochemistry investigations in order to characterize adsorption on well-defined, single crystal electrodes. Below, we will describe the technique and identify some challenging issues which we will be able to address. The proposed method is sensitive to a few percent of a monolayer at smooth surfaces, is nondestructive and simple to use. The radiochemical measurements can be made with all compounds which can be labelled with reasonably long-lived, preferably g- emitting radioisotopes. We believe this technique will fulfill the quantitative function in in situ surface analysis as Auger spectroscopy currently does in vacuum, ex situ characterization of electrodes. 

Surface Electrochemistry Laboratory, Texas A M University, College Station, TX 77843—3255... 

Recently, Carbajal et al. (13) in the Texas A M Surface Electrochemistry Laboratory have been able to show two bonds for FeH, the first (at about 2060 wave numbers) is due to symmetric stretching vibration and the second (at about 980 wave numbers) to the asymmetric stretching vibration. The basic results are shown in Figure 3, where the coverage is plotted against overpotential. 

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