Influence of Atomic Structure, Steps, and Kinks on the Catalytic Activity: In Situ Surface Studies
The surface science approach to catalysis started with the emergence of surface-sensitive techniques that can probe the structure and composition of surfaces. These techniques were made possible by the development of modern vacuum technology . The investigation of surface properties contributed significantly to the development of thin-film technologies for electronics and coatings and, at the same time, provided a basic understanding of surface chemistry and reactions related to catalysis. A substantial number of review articles and books treat the surface science of catalysis until the turn of the millennium. A particularly successful approach was, and still is, to use single crystals to study the surface chemistry of catalysts. The advantage of using single crystals is significant control over the structural features of the surface where the reaction takes place. The crystal face, step orientation, step density, and density of the kinks can be controlled by accurately cutting along specific directions of the bulk crystal. Although the single-crystal surface science approach was successful in providing knowledge of the elementary surface processes of catalysis, it also led to the so-called materials gap (i.e., the difference between the structure and catalytic properties of single crystals and those of complex, real catalysts consisting of nanoparticles on porous oxide supports with the addition of promoters). To bridge this materials gap, surface science studies have shifted towards more complex systems, such as nanoparticles on well-defined oxide surfaces (see Part II). This chapter discusses several examples of recent single-crystal studies. This is not intended to provide a comprehensive, complete overview of recent literature on the subject; instead, it is limited to studies that highlight recent insights on the influence of the atomic structure, steps, and kinks on the catalytic activity of single-crystal surfaces. This chapter is organized as follows: First, the elementary steps of a catalytic reaction and the role of the atomic-scale structure, from the perspective of theoretical calculations, are discussed. Second, the importance of the formation of new structures under realistic reaction conditions for the case of surface oxides is discussed. The third part treats experiments that demonstrate the role of steps in catalytic systems.
KeywordsScanning Tunneling Microscopy Density Functional Theory Calculation Scanning Tunneling Microscopy Image Step Density Chemisorption Energy
I want to thank V. Navarro of Leiden University and J. A. A. W. Elemans of Radboud University Nijmegen for their useful comments and discussion.
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