Common structures of CO₂ on structurally different coin metal surfaces

Area of Science:

• Surface Science
• Materials Science
• Physical Chemistry

Background:

• Understanding molecular adsorption and superstructure formation is crucial for designing novel materials and catalytic processes.
• Carbon dioxide (CO2) adsorption on metal surfaces is relevant for catalysis, climate science, and materials engineering.

Purpose of the Study:

• To investigate the low-temperature superstructures formed by carbon dioxide (CO2) on Ag(100) and Cu(111) surfaces.
• To explore the influence of substrate, temperature, and co-adsorbates on CO2 ordering and layer-by-layer growth.

Main Methods:

• Utilized low-temperature scanning tunneling microscopy (LT-STM) to visualize CO2 structures at the atomic level.
• Grew CO2 films from small clusters to multilayers on defect-engineered Ag(100) and Cu(111) surfaces.

Main Results:

• CO2 nucleation occurs at defects (co-adsorbed CO) on both Ag(100) and Cu(111) surfaces.
• Superstructure symmetry and ordering depend significantly on adsorption temperature and substrate.
• Hexagonal CO2 layers exhibit long-range order, often growing on less ordered underlying layers, suggesting a preferred hexagonal structure.

Conclusions:

• The substrate and temperature critically influence CO2 superstructure formation and long-range order.
• Despite substrate differences, common structural motifs emerge, with hexagonal layers demonstrating superior ordering.
• The findings indicate a general preference for hexagonal packing in CO2 layers on metal surfaces.