Nanoparticles for Heterogeneous Catalysis: New Mechanistic Insights
- 19 December 2012
- journal article
- research article
- Published by American Chemical Society (ACS) in Accounts of Chemical Research
- Vol. 46 (8), 1673-1681
- https://doi.org/10.1021/ar300225s
Abstract
Metallic nanoparticles finely dispersed over oxide supports have found use as heterogeneous catalysts in many industries including chemical manufacturing, energy-related applications and environmental remediation. The compositional and structural complexity of such nanosized systems offers many degrees of freedom for tuning their catalytic properties. However, fully rational design of heterogeneous catalysts based on an atomic-level understanding of surface processes remains an unattained goal in catalysis research. Researchers have used surface science methods and metal single crystals to explore elementary processes in heterogeneous catalysis. In this Account, we use more realistic materials that capture part of the complexity inherent to industrial catalysts. We assess the impacts on the overall catalytic performance of characteristics such as finite particle size, particle structure, particle chemical composition, flexibility of atoms in clusters, and metal–support interactions. To prepare these materials, we grew thin oxide films on metal single crystals under ultrahigh vacuum conditions and used these films as supports for metallic nanoparticles. We present four case studies on specifically designed materials with properties that expand our atomic-level understanding of surface chemistry. Specifically, we address (1) the effect of dopants in the oxide support on the growth of metal nanoclusters; (2) the effects of size and structural flexibility of metal clusters on the binding energy of gas-phase adsorbates and their catalytic activity; (3) the role of surface modifiers, such as carbon, on catalytic activity and selectivity; and (4) the structural and compositional changes of the active surface as a result of strong metal–support interaction. Using these examples, we demonstrate how studies of complex nanostructured materials can help revealing atomic processes at the solid–gas interface of heterogeneous catalysts. Among our findings is that doping of oxide materials opens promising routes to alter the morphology and electronic properties of supported metal particles and to induce the direct dissociation and reaction of molecules bound to the oxide surface. Also, the small size and atomic flexibility of metal clusters can have an important influence on gas adsorption and catalytic performance.Keywords
This publication has 45 references indexed in Scilit:
- Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO OxidationScience, 2008
- Gold Supported on Thin Oxide Films: From Single Atoms to NanoparticlesAccounts of Chemical Research, 2008
- Counting Electrons Transferred through a Thin Alumina Film into Au ChainsPhysical Review Letters, 2008
- Gold CatalysisAngewandte Chemie-International Edition, 2006
- The Structure of Catalytically Active Gold on TitaniaScience, 2004
- Model oxide-supported metal catalysts: energetics, particle thicknesses, chemisorption and catalytic propertiesTopics in Catalysis, 2000
- Metal deposits on well-ordered oxide filmsProgress in Surface Science, 1999
- Onset of Catalytic Activity of Gold Clusters on Titania with the Appearance of Nonmetallic PropertiesScience, 1998
- Surface studies of supported model catalystsSurface Science Reports, 1998
- Handbook of Heterogeneous CatalysisPublished by Wiley ,1997