Surface morphology of atomic nitrogen on Pt(111)

Area of Science:

• Surface Science
• Materials Science
• Physical Chemistry

Background:

• Understanding the adsorption behavior of nitrogen on metal surfaces is crucial for catalysis and materials design.
• The Pt(111) surface is a well-established model system for studying surface reactions and adsorption phenomena.

Purpose of the Study:

• To investigate the atomic-level surface morphology of chemisorbed nitrogen on the Pt(111) surface.
• To characterize the different phases and structures formed by nitrogen adsorption, both alone and in co-adsorption with oxygen.

Main Methods:

• Low-temperature scanning tunneling microscopy (STM) was employed to achieve atomic resolution imaging.
• Systematic variation of nitrogen coverage and temperature was used to study phase transitions and adsorption behavior.

Main Results:

• Co-adsorption of nitrogen and oxygen forms a mixed (2 × 2)-N+O structure.
• At low coverages, isolated nitrogen atoms and incomplete (2 × 2) patches were observed.
• Dense nitrogen layers exhibit coexistence of (√3 × √3)R30°-N and p(2 × 2)-N phases between 360-400 K.
• The (√3 × √3)R30° phase transforms into the (2 × 2) phase upon heating.
• Nitrogen atoms occupy fcc-hollow sites in both observed phases.
• Nitrogen desorption begins above 420 K.
• The p(2 × 2)-N phase displays a honeycomb structure, indicative of strong nitrogen-platinum binding.

Conclusions:

• Nitrogen adsorption on Pt(111) leads to diverse surface structures and phase transitions dependent on coverage and temperature.
• The p(2 × 2)-N phase, characterized by a honeycomb structure, highlights the strong interaction between nitrogen and the platinum surface.