The effect of surface coverage on N₂, NO and N₂O formation over Pt(111)

Area of Science:

• Surface Science
• Chemical Kinetics
• Computational Chemistry

Background:

• Ammonia oxidation over platinum is crucial for industrial processes and catalysis.
• Understanding the influence of surface coverage on reaction kinetics is essential for catalyst design.

Purpose of the Study:

• To investigate the effect of surface coverage (θ) on the kinetic parameters of N2, NO, and N2O formation during ammonia oxidation on Pt(111).
• To elucidate how varying surface coverage impacts reaction pathways and intermediate binding energies.

Main Methods:

• Utilized periodic density functional theory (DFT) calculations to simulate ammonia oxidation on a Pt(111) surface.
• Analyzed energy barriers, heats of surface reaction, and binding energies for various surface coverages.

Main Results:

• Energy barriers for product formation decrease with increasing surface coverage (θ), particularly above 0.25 ML.
• Increased θ leads to decreased heat of surface reaction, reducing product dissociation due to weaker intermediate-surface interactions.
• Nitrogen adatom (N*) coverage has a more pronounced effect on binding energies and activation energies for desorption compared to oxygen (O*) or nitrogen monoxide (NO*) adatoms.

Conclusions:

• Surface coverage is a critical factor controlling the kinetics and thermodynamics of ammonia oxidation on Pt(111).
• The findings provide insights into optimizing catalytic performance by managing surface species concentrations.