Model Systems in Heterogeneous Catalysis: Selectivity Studies at the Atomic Level

Abstract

Reaching 100% selectivity is the theme of the twentyfirst century in heterogeneous and heterogenized homogeneous catalysis. To study chemical reactivity at the atomic scale, model systems have been prepared and characterized. We discuss selectivity of hydrogenation and dehydrogenation reactions on supported Pd particles, methanol oxidation at vanadium oxide model catalysts and, at last, the design of model catalysts with a well defined charge state of the metal, i.e., Au catalyst model systems.

Catalysis with Supported Size-selected Pt Clusters

“…Different light off temperatures and consequently different hysteresis curves are observed for the different samples. The smallest size Pt 10 does not yet show a light off or full conversion, however the increasing slope is a sign for reactivity of this sample at higher temperatures. Except for the 9 nm particles a lower light off temperature with increasing cluster size can be observed, for Pt 68 the reactivity resembles the one of the thin film.…”

“…2.2.3) states strongly influencing the peak shape and intensity of the MIE spectra [173,246,323]. 10 As visible from tab. 4.4.1 and fig.…”

“…spectroscopy, usually model systems with reduced complexity and trying to mimic real catalysts are used in order to understand catalytic phenomena [7]. In the early days of surface science these systems were predominantly single crystal surfaces [8], that evolved into supported particles [9,10], which still often lack the complexity of real catalyst materials. A particularly sophisticated and advanced model systems are supsupported size-selected clusters ported, size-selected metal clusters, with a precision of designing a catalyst atom by atom [11].…”

“…This observation is tentatively interpreted by means of photo generated electrons being dis-tributed among more and more Pt clusters for increasing coverage. 10 The threshold for saturation is expected for distances between the Pt clusters comparable to the spatial extent of the electronic wave functions. In the present case, this allows for estimating this distance to 5 to 8 nm [220].…”

Simulating the Complexities of Heterogeneous Catalysis with Model Systems: Case studies of SiO2 Supported Pt-Group Metals

“…In the following article, we will restrict our focus on investigations utilizing planar model catalyst surfaces which are prepared via vapor deposition techniques [1][2][3][4][5][6][7][8][9][10][11]. These ''model'' surfaces consist of a planar oxide support (e.g.…”