Atomically Resolved Chemical Reactivity of Small Fe Clusters

Area of Science:

• Surface Science
• Nanotechnology
• Catalysis

Background:

• Small metal clusters are vital catalysts, with reactivity often linked to size and edges.
• Previous studies suggested reactivity increases with cluster size, but individual atom behavior remained unmeasured.

Purpose of the Study:

• To directly measure the chemical reactivity of individual atoms within iron (Fe) clusters.
• To investigate the relationship between atomic coordination and reactivity in Fe clusters.

Main Methods:

• Utilized scanning probe microscopy with CO-terminated tips to probe chemical binding forces.
• Assembled and studied Fe clusters atom-by-atom, ranging from 1 to 15 atoms.
• Correlated atomic force microscopy (AFM) images with force spectra.

Main Results:

• Individual atom reactivity in flat Fe clusters is determined by coordination number, not overall cluster size.
• Atomic contrast in AFM images was explained by relating force spectra to atomic positions.
• Demonstrated atomic-scale control over cluster assembly and reactivity.

Conclusions:

• Coordination number is the key factor governing the chemical reactivity of individual atoms in Fe clusters.
• Scanning probe microscopy provides unprecedented insight into atomic-scale catalytic mechanisms.
• Findings challenge previous assumptions about size-dependent reactivity in small metal clusters.