Initial oxidation of the Rh(110) surface: ordered adsorption and surface oxide structures

Area of Science:

• Surface science
• Materials science
• Physical chemistry

Background:

• Understanding the initial oxidation of transition metal surfaces is crucial for catalysis and materials development.
• Rhodium surfaces are known for their catalytic activity, making their oxidation behavior a key research area.

Purpose of the Study:

• To investigate the initial oxidation of the Rh(110) surface using experimental and theoretical methods.
• To characterize the resulting surface oxide structures and compare them with other Rh basal planes.

Main Methods:

• Scanning tunneling microscopy (STM) for atomic-scale surface imaging.
• Core level spectroscopy (CLS) for chemical state analysis.
• Density functional theory (DFT) for theoretical modeling and phase diagram prediction.

Main Results:

• Exposure to molecular oxygen leads to a monolayer oxide with (10x2) and (2x1) phases.
• Atomic oxygen facilitates further oxidation, forming a c(2x4) surface oxide.
• The c(2x4) structure resembles hexagonal trilayer oxides found on Rh(111) and Rh(100).
• Thermodynamic predictions suggest some observed phases may be kinetically hindered.

Conclusions:

• The c(2x4) structure represents a stable surface oxide on Rh(110), similar to those on other Rh substrates.
• Kinetic factors play a significant role in the observed surface oxide formation, potentially leading to metastable phases.
• Comparison with bulk oxides (RhO2, Rh2O3) provides further context for surface oxide stability.