The Institute for Catalysis in Energy Processes (ICEP) is composed of a number of collaborative research efforts between the Northwestern University Center for Catalysis and Surface Science and Argonne National Laboratory. The overall scientific goals of ICEP are to understand at the molecular level catalytic and photocatalytic transformations relevant to energy harvesting, storage, and utilization and to further the discovery and development of highly efficient catalytic and photocatalytic processes.
ICEP is organized into three (3) subtasks.
Work in Subtask 1 is composed of three efforts: Transformation of Oxide Surface Structures, Metal and Metal-Oxide Catalysts on Oxide Supports, and Methods Development.
The determination of real oxide surface atomic positions that result from pretreatments that are typical of catalyst synthesis is a major accomplishment of the first effort. This work has opened a window into the inherent complexity of oxide surfaces caused by non-uniform composition, the requirements of charge balance, the variable size and oxidation states of metal cations, etc. It has become abundantly clear that our intuition about how the bulk oxide terminates at the free surface remains very poor so this work will continue. At the same time we have developed a substantial effort to explore the chemical implications of the various surface structures.
The second effort primarily makes use of the X-ray Standing Wave (XSW) measurement developed within ICEP. This method provides model-independent, real space atomic structures of catalytic clusters and overlayers on an oxide support. Since the measurements can be performed under realistic reaction conditions, the present work is focused on determining the atomic structures of supported vanadium oxide associated with various points around a catalytic redox cycle.
The third effort has both experimental and computational parts. The development of Surface Enhanced Raman Spectroscopy as a tool to monitor reactions at the liquid-solid interface will make it possible to study molecular processes that occur during heterogeneous catalysis in liquid environments. We believe this capability will allow us to study the aqueous heterogeneous catalytic reactions of relevance to biomass conversion. Our ability to determine surface atomic structures has been and will continue to be directly reliant on developments in computational methods.
Subtask 2 is an activity primarily at Argonne National Laboratory and is composed of three efforts: Synthesis of Nanostructured Membrane Catalyst Systems, Experiments on Catalytic Selective Oxidation, and Computational Investigations of Catalytic Structure/Function Relationships.
Nanostructured membranes, fabricated by a combination of anodic aluminum oxidation (AAO) and atomic layer deposition (ALD) possess most, if not all, the features of the ideal nanostructured membrane topology. They offer novel catalyst environments which:
1) provide larger, controllable pore sizes than conventional mesoporous materials (for containing large clusters or arrays of catalyst sites, for efficient in-diffusion of large/elaborate molecular precursors or feedstock molecules, and for out-diffusion of large/elaborate product molecules),
2) permit tailoring of channel size and wall composition by ALD,
3) constrain catalyst mobility, thus hindering agglomeration,
4) control flow of reagents in, out, and through the catalyst structure.
Several formulations of supported vanadium oxide catalysts have been prepared that differ according to the loading of vanadium, the method of deposition (wet impregnation and ALD), and the supporting oxide (Al2O3, TiO2, Nb2O5). The membrane materials have been characterized by XRD, XRF, SAXS, UV Raman, and EPR. The oxidative dehydrogenation of cyclohexane and propane catalyzed by the various membranes has been studied at a series of reaction temperatures, and interesting changes in activity and selectivity have been studied.
Work in Subtask 3 is composed of two efforts: Catalytic Chemical Transformations and Photo/Electrocatalytic Transformations.
The effort on Chemical Catalysis has shifted its focus from reduction of nitrogen oxides in an oxygen-rich atmosphere to tackling the challenges in selective catalytic oxidation of light alkanes using molecular oxygen. The overall goals are to achieve a fundamental understanding of factors that influence elementary catalytic reaction steps and to employ the knowledge gained to advance the development of highly effective catalytic systems, with an emphasis on designing nanostructured materials.
In Photocatalysis a previous effort on mineralization of organic molecules, particularly those important in indoor air pollution, has shifted to elucidating the mechanism for photocatalytic reduction of CO2 (e.g. to CO and methanol) and to understanding the effect of catalyst morphology and structure on the mechanism and efficiency of photocatalysis.
A new effort has been initiated to study Electrocatalysis by metal and oxide nanoparticles supported on carbon nanotubes.
Institute for Interfacial Catalysis
Center for Catalysis and Surface Science | 2137 Sheridan Road | Evanston IL 60208
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