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Reversible dynamic behavior in catalyst systems: oscillations of structure and morphology
S Surnev1, J Schoiswohl, G Kresse
1Institut für Experimentalphysik, Karl-Franzens-Universität Graz, Austria. svetlozar.surnev@uni-graz.at
Physical Review Letters
|December 18, 2002
Summary
Vanadium oxide nanoparticles on palladium surfaces exhibit a reversible wetting-dewetting behavior. This dynamic surface restructuring is driven by changes in reducing and oxidizing conditions, altering oxide coverage.
Area of Science:
- Surface science
- Materials science
- Nanotechnology
Background:
- Vanadium oxide nanoparticles on metal surfaces are technologically relevant.
- Understanding their dynamic behavior under varying chemical environments is crucial.
Purpose of the Study:
- To investigate the atomic-level mechanism of vanadium oxide nanoparticle spreading and dewetting on a Pd(111) surface.
- To establish a surface oxide phase stability diagram for vanadium oxide on Pd(111).
Main Methods:
- In situ variable-temperature scanning tunneling microscopy (STM) was employed to observe the dynamic process at the atomic scale.
- Density functional theory (DFT) calculations were used to determine the surface oxide phase stability diagram.
Main Results:
- Reducing conditions induce spreading of vanadium oxide, leading to full surface coverage by a reduced oxide phase.
- Reoxidation reverses the process, forming oxide islands and exposing bare metal patches.
- The study reveals a distinct wetting-dewetting behavior governed by oxygen chemical potential and vanadium concentration.
Conclusions:
- The wetting-dewetting behavior of vanadium oxide on Pd(111) is a thermally and chemically driven process.
- The established phase diagram provides a framework for predicting surface structure under different conditions.
- Atomic-level insights into nanoparticle dynamics are crucial for designing surface-based catalytic and electronic devices.