CO Activation on Silver Clusters: How Valence Electrons, Geometry, and p Back-Donation Dictate Reactivity

Area of Science:

• Physical Chemistry
• Materials Science
• Surface Science

Background:

• Transition metal clusters are promising for environmental remediation.
• Understanding CO adsorption on silver clusters is crucial but complex.
• Site-specific binding mechanisms governed by cluster properties remain unclear.

Purpose of the Study:

• Investigate gas-phase CO reactions with silver clusters (Ag_n^-, n = 10-25).
• Determine how silver cluster properties influence carbon monoxide adsorption.
• Assess charge effects on CO adsorption using Ag_n^+,0 clusters.

Main Methods:

• Utilized time-of-flight mass spectrometry (TOF-MS) for cluster analysis.
• Employed density functional theory (DFT) for theoretical investigations.
• Studied CO adsorption on neutral, anionic, and cationic silver clusters.

Main Results:

• Observed enhanced CO reactivity for clusters with fewer than 18 valence electrons.
• Identified odd-even oscillations in adsorption energy, declining from 18-22 electrons, and rebounding beyond 23.
• Key factors include high-coordination site stabilization, orbital interactions (σ, π, and p back-donation), C-Ag* bond hybridization, and jellium electron counting.

Conclusions:

• Atomic-scale insights into CO adsorption mechanisms on silver clusters were provided.
• Cluster size, electronic structure, and atomic packing significantly impact CO binding.
• Findings advance the understanding of catalytic processes involving silver clusters.