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Published on: February 7, 2017
Low-temperature reduction of NO(2) on oxidized Mo(110)
L J Deiner1, D-H Kang, C M Friend
1Department of Chemistry and Division of Engineering and Applied Science, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Nitrogen dioxide (NO2) reactions on oxidized Molybdenum (Mo)(110) surfaces produce nitrogen (N2) and nitric oxide (NO). NO2 acts as a stronger oxidant than O2, depositing more oxygen onto the Mo surface.
Area of Science:
- Surface Science
- Chemical Kinetics
- Oxidation Reactions
Background:
- Understanding the reactivity of nitrogen dioxide (NO2) on metal oxide surfaces is crucial for catalysis and environmental science.
- Oxidized Molybdenum (Mo)(110) surfaces, featuring chemisorbed oxygen and thin oxide films, present complex reaction environments.
Purpose of the Study:
- To investigate the reaction pathways and products of NO2 interacting with oxidized Mo(110) surfaces.
- To compare the oxidizing and reactive properties of NO2 with O2 on these surfaces.
- To elucidate the role of surface oxygen species in NO2 reduction and N-containing product formation.
Main Methods:
- Utilizing infrared spectroscopy to identify adsorbed species (N2O4, NO2, NO) at low temperatures (100 K).
- Employing isotopically labeled oxygen ((18)O) to trace oxygen transfer and exchange mechanisms.
- Analyzing product distribution (NO, N2, N2O) as a function of temperature (below 200 K and higher).
Main Results:
- NO2 undergoes reversible adsorption and reduction to NO and N2 on both oxidized Mo(110) surfaces below 200 K.
- The surface with chemisorbed oxygen, having a lower oxidation state, more effectively reduces NO2.
- NO2 is a stronger oxidant than O2, depositing more oxygen, particularly Mo=O moieties, onto the surface.
- Selectivity for N2 formation over N2O is higher for NO2 compared to NO reactions.
Conclusions:
- NO2 reactions on oxidized Mo(110) involve adsorption, reduction, and partial dissociation, yielding NO and N2 as primary products.
- Surface oxygen species, especially Mo=O, significantly influence NO2 reactivity and product selectivity.
- NO2 demonstrates superior oxidizing capability compared to O2 on these Mo surfaces, with evidence of oxygen transfer even at low temperatures.
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