Model studies in heterogeneous catalysis at the microscopic level: from the structure and composition of surfaces to reaction kinetics

Abstract

Heterogeneous catalysis is one of the fields of modern technology, in which a characterization of structural and chemical properties of solid surfaces at the microscopic level is of enormous importance. For a long time, such insights have been precluded by the complexity of most catalytically active materials. Recently, substantial progress has been made, however, toward a microscopic-level understanding of complex catalyst surfaces. We discuss the driving factors for these advancements, which are based on the development of new well-defined model systems as well as on advances in experimental technology and theory. Scrutinizing the example of planar model catalysts, we identify the process of linking structural and chemical information to microscopic reaction kinetics as a particular challenging aspect of today's work. We review the kinetic effects which may have an influence on the reaction kinetics on complex surfaces. As an example how structural and kinetic information can be correlated at the microscopic level we discuss the case of surface oxidation and oxygen induced restructuring of Pd nanoparticles as studied by molecular beam methods.

A versatile instrument for ambient pressure x-ray photoelectron spectroscopy: The Lund cell approach

“…[1][2][3][4]). This circumstance has been termed the "pressure gap" which exists alongside the "materials gap" related to the much higher structural complexity of real materials in comparison to the idealised samples of surface science.…”

Statistical analysis of support thickness and particle size effects in HRTEM imaging of metal nanoparticles

“…As an example of the latter, metal nanoparticles supported by high surface area materials are common heterogeneous catalysts and important to myriad industrial processes [15]. Model systems of supported metal nanoparticles on planar substrates is a common approach for exploring the microscopic processes otherwise obscured by the complexity of these materials [16]. McBride et al [17] indicated that conventional TEM imaging of ultra-small NPs can be limited by particle diameters of greater than 3 nm due to the contrast from amorphous carbon support films.…”

Preparation and Adsorption Properties of Pd Nanoparticles Supported on TiO2Nanotubes

“…[23][24][25] Large effects are also expected for supported nanoparticles on TiNTs, as the support structure may have a great influence on the adsorption properties and reactivity. [26][27][28] In this work, we explore the preparation and characterization of noble-metal-loaded TiNTs using an integrated surface-science approach. The systems prepared may offer unique opportunities, for example: (i) the metal nanoparticle distribution in the TiNTs can be controlled, and its influence on the adsorption and reaction kinetics could be studied (and utilized toward the optimization of catalytic properties), and (ii) the influence of the TiNTs' morphology and structure on the adsorption and catalytic properties could be investigated in great detail.…”

“…Better insight into the interaction of gases with pure and metal-loaded TiNTs could be obtained by suitable model catalyst studies. First studies on pure TiNTs have indeed indicated pronounced structure dependencies. − Large effects are also expected for supported nanoparticles on TiNTs, as the support structure may have a great influence on the adsorption properties and reactivity. − …”