Emergence of Subsurface Oxygen on Rh(111)

Area of Science:

• Surface Science
• Heterogeneous Catalysis
• Materials Chemistry

Background:

• Oxygen atoms exhibit high mobility on transition metal surfaces under reaction conditions.
• Subsurface oxygen plays a critical role in oxidized metal catalyst chemistry, but its formation and egress mechanisms are poorly understood.
• Oxygen diffusion between surface and subsurface sites, potentially mediated by defects, can lead to localized changes in surface reactivity.

Purpose of the Study:

• To investigate the behavior and preferential emergence sites of subsurface oxygen on transition metal surfaces.
• To understand the relationship between subsurface oxygen dynamics and surface oxide decomposition.
• To elucidate the role of surface phase boundaries in oxygen diffusion.

Main Methods:

• In-situ surface science techniques were employed to observe oxygen atom mobility and subsurface diffusion.
• High-resolution microscopy and spectroscopy were used to identify surface phases and oxygen emergence sites.
• Controlled oxidation and decomposition experiments were performed to study oxygen dynamics.

Main Results:

• Oxygen atoms were observed to emerge preferentially along the boundaries between distinct surface phases.
• Subsurface oxygen was found to be depleted prior to the complete decomposition of the surface oxide layer.
• Evidence suggests that defects and phase boundaries act as preferential pathways for oxygen diffusion.

Conclusions:

• Subsurface oxygen dynamics are strongly influenced by surface morphology and phase heterogeneity.
• The preferential emergence of subsurface oxygen at phase boundaries impacts localized surface chemistry and catalytic activity.
• Understanding these subsurface oxygen transport mechanisms is crucial for designing and optimizing heterogeneous oxidation catalysts.