Coverage-dependent adsorption and desorption of oxygen on Pd(100)
Angela den Dunnen1, Leon Jacobse1, Sandra Wiegman1
1Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
The Journal of Chemical Physics
|July 3, 2016
Summary
Oxygen adsorption on Palladium(100) surfaces dissociates directly. High kinetic energy and low temperatures create unexpected high atomic oxygen coverages, suggesting phonon excitation is key.
Area of Science:
- Surface Science
- Chemical Physics
- Materials Science
Background:
- Understanding gas-surface interactions is crucial for catalysis and materials development.
- Oxygen adsorption on metal surfaces is a fundamental process with implications for oxidation and surface functionalization.
- Palladium (Pd) is a key catalyst, and its interaction with oxygen is extensively studied.
Purpose of the Study:
- To investigate the adsorption and desorption dynamics of molecular oxygen (O2) on a Palladium(100) surface.
- To determine the influence of kinetic energy and surface temperature on oxygen dissociation and overlayer formation.
- To elucidate the mechanisms governing high atomic oxygen coverage on Pd(100).
Main Methods:
- Supersonic molecular beam techniques to control oxygen reactant energy.
- Thermal desorption spectroscopy (TDS) to analyze surface species and coverages.
- Systematic variation of kinetic energies (56–380 meV) and surface temperatures (100–600 K).
Main Results:
- Oxygen (O2) dissociates directly on the bare Pd(100) surface across a wide range of kinetic energies and temperatures.
- Low temperatures (≤150 K) lead to a mixed O/O2 overlayer, with subsequent O2 dissociation yielding unexpectedly high atomic oxygen coverages.
- High incident kinetic energy and high surface temperature also promote high final atomic oxygen coverages, a phenomenon not observed at intermediate conditions.
- Activated nucleation of high-coverage surface structures is facilitated by reactant kinetic energy and dissipated reaction energy.
Conclusions:
- Both gas-phase reactant kinetic energy and energy dissipation during O2 dissociation contribute to activated nucleation of high-coverage surface structures on Pd(100).
- The formation of high atomic oxygen coverages is dependent on specific energy regimes and surface conditions.
- Excitation of local substrate phonons is proposed as a critical factor enabling oxygen dissociation across all coverages.
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