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Microscopic diffusion processes of NO on the Pt997 surface.

Noriyuki Tsukahara¹, Kozo Mukai, Yoshiyuki Yamashita

¹The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.

The Journal of Chemical Physics

|February 13, 2008

Summary

Nitric oxide (NO) molecules were observed to migrate across platinum surfaces at low temperatures. Researchers mapped NO diffusion pathways and energy barriers on Pt(997), revealing specific adsorption sites and migration dynamics.

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Area of Science:

Surface Science
Physical Chemistry
Materials Science

Background:

Understanding molecular diffusion on surfaces is crucial for catalysis and materials design.
The Pt(997) surface offers diverse adsorption sites, including terraces and step edges, influencing diffusion behavior.
Low-coverage NO adsorption on platinum surfaces presents a model system for studying fundamental surface dynamics.

Purpose of the Study:

To investigate the microscopic diffusion processes of nitric oxide (NO) molecules on the Pt(997) surface at low coverage.
To identify and characterize various adsorption sites for NO on Pt(997) at cryogenic temperatures.
To quantify the migration barriers and kinetics of NO diffusion between different adsorption sites.

Main Methods:

Time-resolved infrared reflection absorption spectroscopy (TR-IRAS) was employed to monitor NO adsorption and diffusion.
Kinetic Monte Carlo (KMC) simulations were used in conjunction with experimental data.
Experiments were conducted at various low temperatures (11 K to 110 K) to probe different diffusion regimes.

Main Results:

Four distinct adsorption sites (OT, HT, BS, HS) for NO on Pt(997) were identified at 11 K, with a mean lateral displacement of 4.1 Å.
Migration of hollow sites at the step (HS) to bridge sites at the step (BS) was observed with a barrier of ~120 meV.
Diffusion from on-top (OT) to hollow terrace (HT) sites occurred with an activation barrier of 200 meV, while HT to BS migration had a barrier of 290 meV.

Conclusions:

A quantitative microscopic picture of NO migration on the Pt(997) surface has been established.
The study provides detailed insights into the energetic landscape governing NO diffusion on stepped platinum surfaces.
The findings contribute to a fundamental understanding of surface processes relevant to heterogeneous catalysis.