NO(2) dissociation on Ag(111) revisited by theory

Area of Science:

• Surface Science
• Chemical Physics
• Computational Materials Science

Background:

• Nitrogen dioxide (NO2) adsorption and dissociation on metal surfaces are crucial for understanding catalytic processes and atmospheric chemistry.
• Experimental studies have observed NO2 dissociation on Ag(111) at low temperatures, a phenomenon not readily explained by simple adsorption models.

Purpose of the Study:

• To investigate the mechanism of NO2 dissociation on the Ag(111) surface using first-principles calculations.
• To reconcile the theoretical findings with experimental observations of low-temperature dissociation.

Main Methods:

• First-principles density functional theory (DFT) calculations were employed to model NO2 adsorption and dissociation pathways on Ag(111).
• Analysis included potential energy surfaces and adsorption energies for single NO2 molecules.

Main Results:

• Calculations for isolated NO2 molecules show a high adsorption potential energy barrier, effectively prohibiting dissociation.
• Thermodynamic and potential energy surface irregularities were insufficient to explain the experimental dissociation rates.
• A discrepancy between theoretical predictions for single molecules and experimental findings at low temperatures was identified.

Conclusions:

• The high adsorption energy of single NO2 molecules on Ag(111) does not support dissociation.
• Collective reaction mechanisms, specifically Eley-Rideal type pathways involving multiple molecules, are proposed as the likely drivers for the experimentally observed low-temperature dissociation.
• Further theoretical and experimental investigations into multi-molecule reaction dynamics are warranted.