Surface science approach

How are fiindamental aspects of surface reactions studied The surface science approach uses a simplified system to model the more complicated real-world systems. At the heart of this simplified system is the use of well defined surfaces, typically in the fonn of oriented single crystals. A thorough description of these surfaces should include composition, electronic structure and geometric structure measurements, as well as an evaluation of reactivity towards different adsorbates. Furthemiore, the system should be constructed such that it can be made increasingly more complex to more closely mimic macroscopic systems. However, relating surface science results to the corresponding real-world problems often proves to be a stumbling block because of the sheer complexity of these real-world systems. 

This chapter will explore surface reactions at the atomic level. A brief discussion of corrosion reactions is followed by a more detailed look at growth and etchmg reactions. Finally, catalytic reactions will be considered, with a strong emphasis on the surface science approach to catalysis. 

Surface science studies of catalytic reactions certainly have shed light on the atomic-level view of catalysis. Despite this success, however, two past criticisms of the surface science approach to catalysis are that the... 

Jaegermann, W. The Semiconductor/Electrolyte Interface A Surface Science Approach 30... 

The surface science approach (Eq. 5.14) has the important advantage that both d>and are measurable quantities. This is not the case for the electrochemical approach (Eq. 5.15) since neither the chemical potential p nor the Galvani potential tp are measurable quantities. Only changes in tp are measurable. 

Similar considerations apply to the oxidation of ethanol, although one must take into account the breaking of the C—C bond, and the formation and involvement of different intermediates and side products. Ethanol oxidation will be the topic of Section 6.5. Section 6.6 will briefly summarize our main conclusions and discuss the relation of our surface science approach to real catalysts. 

In this chapter, we have summarized (recent) progress in the mechanistic understanding of the oxidation of carbon monoxide, formic acid, methanol, and ethanol on transition metal (primarily Pt) electrodes. We have emphasized the surface science approach employing well-defined electrode surfaces, i.e., single crystals, in combination with surface-sensitive techniques (FTIR and online OEMS), kinetic modeling and first-principles DFT calculations. 

Fuel Cell Catalysis A Surface Science Approach, Edited by Marc T. M. Koper... 

Nieuwenhuys, B.E. (2000) The surface science approach toward understanding automotive exhaust conversion catalysis at the atomic level, Adv. Catal. 44, 35. 

The strength of the surface science approach is that it can address the molecular details of catalytic issues by pooling information from a battery of specific analytical spectroscopies and techniques [174], As more complex model systems are developed, the wealth of characterization techniques available in vacuum environments can be used to better understand catalysis. 

The sketched examples represent just the tip of the iceberg called heterogeneous catalysis. An excellent account of the historical development as well as of the current state of the art can for example be found in a recent review by J. M. Thomas. [30] A few of the additional effects for which understanding can also be sought on the basis of file surface science approach will only be briefly listed ... 

In recent years the surface science approach has led to a dramatic increase in our knowledge of the surface chemistry and kinetics. Processes that have been studied using the surface science approach include the deposition and etching of semiconductors (e.g., Si, Ge,... 

In the traditional surface science approach the surface chemistry and physics are examined in a UHV chamber at reactant pressures (and sometimes surface temperatures) that are normally far from the actual conditions of the process being investigated (catalysis, CVD, etching, etc.). This so-called pressure gap has been the subject of much discussion and debate for surface science studies of heterogeneous catalysis, and most of the critical issues are also relevant to the study of microelectronic systems. By going to lower pressures and temperatures, it is sometimes possible to isolate reaction intermediates and perform a stepwise study of a surface chemical mechanism. Reaction kinetics (particularly unimolecular kinetics) measured at low pressures often extrapolate very well to real-world conditions. 

W. Jaegermann, in Modem Aspects of Electrochemistry, (R. E. White, B. E. Conway, J. O M. Bockris, eds.), pi36 (The semiconductor/electrolyte interface a surface science approach), Plenum, New York (1996). 

The studies discussed above deal with highly dispersed and therefore well-defined rhodium particles with which fundamental questions on particle shape, chemisorption, and metal support interactions can be addressed. Often, such catalysts are prepared from different starting materials, such as organometallic clusters [28] and carbonyls [29] than are used in industry. Noteworthy are also the studies on evaporated rhodium clusters on planar supports, as have been studied extensively in surface science approaches [5, 30-32]. 

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