Identifying reaction intermediates and catalytic active sites through in situ characterization techniques
1Center for Catalytic Science and Technology, Department of Chemical Engineering, University of Delaware, Newark, DE 19716, USA.
Chemical Society Reviews
|November 2, 2010
Summary
This review highlights advanced in situ experimental techniques for characterizing catalyst surfaces and species. It covers infrared spectroscopy, solid-state NMR, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy for detailed analysis.
Area of Science:
- Catalysis
- Surface Science
- Spectroscopy
Background:
- Characterizing catalysts under working conditions is crucial for understanding reaction mechanisms.
- Traditional ex situ methods often fail to capture dynamic surface changes during catalysis.
Purpose of the Study:
- To review recent advances in experimental techniques for in situ catalyst characterization.
- To emphasize methods providing information on surface species and catalyst structures under reaction conditions.
Main Methods:
- Infrared (IR) spectroscopy, including Sum Frequency Generation (SFG) and Polarization Modulation-infrared reflection absorption spectroscopy (PM-IRRAS).
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy for surface species and intermediates.
- High-pressure X-ray Photoelectron Spectroscopy (HP-XPS) for supported catalysts.
- X-ray Absorption Spectroscopy (XAS), including X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS), under reaction conditions.
Main Results:
- IR techniques provide insights into the concentration and identity of surface species during catalysis.
- Solid-state NMR aids in detecting surface species and reaction intermediates.
- HP-XPS offers valuable information on supported catalysts.
- XAS, particularly under reaction conditions, reveals structural and chemical changes of surface atoms.
Conclusions:
- Advanced in situ spectroscopic techniques are essential for a comprehensive understanding of catalytic processes.
- These methods enable detailed characterization of surface species and catalyst structures under dynamic reaction environments.
- The reviewed techniques offer powerful tools for designing and optimizing future catalysts.
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