Steric effect in CO oxidation on Pt(111).
Hirokazu Ueta1, Mitsunori Kurahashi1
1National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan.
The Journal of Chemical Physics
|November 23, 2017
Summary
The rate of carbon monoxide (CO) oxidation on platinum (Pt) surfaces is significantly influenced by the orientation of incoming oxygen (O2) molecules. Specifically, O2 adsorption and CO oxidation on Pt(111) occur only when O2 is oriented parallel to the surface.
Area of Science:
- Surface science
- Chemical kinetics
- Heterogeneous catalysis
Background:
- The oxidation of carbon monoxide (CO) on platinum surfaces is a fundamental reaction in heterogeneous catalysis.
- Understanding the elementary steps of this reaction, such as oxygen adsorption, is crucial for catalyst design.
- The role of molecular orientation in surface reactions is an active area of research.
Purpose of the Study:
- To investigate the influence of incident oxygen molecule (O2) geometry on the rate of CO oxidation on a platinum(111) surface.
- To determine the conditions under which O2 adsorption and CO oxidation occur on CO-covered Pt(111).
Main Methods:
- Experimental measurements of O2 sticking probability and CO2 production rate.
- Utilizing an alignment-controlled O2 molecular beam.
- Conducting experiments on CO-covered Pt(111) surfaces at a surface temperature of 330 K.
Main Results:
- The rate of CO oxidation on Pt(111) is strongly dependent on the orientation of the incident O2 molecule.
- Both O2 adsorption and CO oxidation were observed to proceed exclusively when the O2 molecular axis was nearly parallel to the Pt(111) surface.
- This effect was noted at specific translational energies (0.1-0.2 eV) and CO coverages (<0.4 monolayers).
Conclusions:
- The adsorption and subsequent reaction of O2 on Pt(111) are highly sensitive to the molecule's initial orientation.
- Molecular orientation plays a critical role in controlling the kinetics of CO oxidation on platinum surfaces.
- These findings provide insights into the mechanism of CO oxidation and have implications for catalytic processes involving O2 activation.
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