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How low can you go? Minimum energy pathways for O2 dissociation on Pt(111)
1The Gene and Linda Voiland School of Chemical and Bioengineering, Washington State University, Pullman, Washington 99164, USA.
Physical Chemistry Chemical Physics : PCCP
|October 25, 2012
Summary
This study clarifies oxygen (O(2)) dissociation on platinum (Pt(111)) surfaces. It identifies interconnected pathways and a direct route consistent with experiments, revealing coverage effects on activation barriers.
Area of Science:
- Surface Science
- Computational Chemistry
- Catalysis
Background:
- Density Functional Theory (DFT) studies on O(2) dissociation on Pt(111) have yielded conflicting results regarding preferred reaction pathways and final states.
- Understanding these pathways is crucial for catalytic applications involving platinum surfaces.
Purpose of the Study:
- To resolve conflicting DFT findings on O(2) dissociation on Pt(111).
- To investigate and compare O(2) adsorption and dissociated states on Pt(111) using large unit cells.
- To elucidate the interconnectedness of various dissociation pathways and the influence of co-adsorbed species.
Main Methods:
- Large p(4 × 4) unit cell minimum energy pathway evaluations using Density Functional Theory (DFT).
- Comparison of O(2) adsorption and dissociated states on Pt(111).
- Construction of a Brønsted-Evans-Polanyi relationship to quantify coverage dependence.
Main Results:
- Identified interconnected pathways for O(2) dissociation from top-fcc-bridge, top-hcp-bridge, and top-bridge-top sites.
- Revealed a direct reaction pathway from top-fcc-bridge to hcp and fcc sites, aligning with experimental observations.
- Demonstrated significant perturbation of this pathway by co-adsorbed oxygen atoms.
- Established that pathways originating from the top-fcc-bridge site exhibit the lowest activation barriers for O(2) dissociation.
Conclusions:
- The top-fcc-bridge site is the most favorable for O(2) dissociation on Pt(111).
- Co-adsorbed oxygen significantly impacts dissociation pathways and energetics.
- A Brønsted-Evans-Polanyi relationship effectively models the coverage dependence of O(2) dissociation activation energies.
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