Dynamic Restructuring Induced Oxygen Activation on AgCu Near-Surface Alloys

Area of Science:

• Surface Science
• Catalysis
• Materials Science

Background:

• Silver (Ag) catalysts are crucial for epoxidation reactions.
• Bimetallic catalysts, particularly Ag-Cu alloys, show enhanced selectivity and performance.
• Understanding the atomistic mechanisms of oxygen activation on these surfaces is key.

Purpose of the Study:

• To investigate the atomistic behavior of oxygen (O2) dissociation on AgCu near-surface alloys.
• To elucidate the role of copper (Cu) in enhancing the catalytic activity of silver (Ag) surfaces.
• To explain the observed nonlinear effects in O2 activation.

Main Methods:

• Preparation of AgCu near-surface alloys.
• Scanning tunneling microscopy (STM) for atomic-level imaging of O2 dissociation.
• Density functional theory (DFT) calculations to determine energy barriers and surface interactions.

Main Results:

• AgCu surfaces exhibit a higher O2 dissociative sticking probability compared to pure Ag(111).
• DFT calculations confirm a reduced O2 dissociation barrier (0.17 eV lower) on the AgCu alloy.
• An exponential increase in O2 sticking probability was observed after initial uptake, linked to surface oxygen.
• Surface oxygen was found to reverse segregation energy, stabilizing Cu atoms in the Ag surface layer.

Conclusions:

• Single Cu atoms stabilized in the Ag surface significantly lower the O2 dissociation barrier.
• The findings explain nonlinear effects in O2 activation on AgCu surface alloys.
• This work provides atomistic insights into the enhanced catalytic performance of AgCu systems.