Pd6O4+: an oxidation resistant yet highly catalytically active nano-oxide cluster

Area of Science:

• * Nanoscale inorganic chemistry
• * Heterogeneous catalysis
• * Surface science

Background:

• * Understanding the reactivity of bare metal clusters with oxidants is crucial for catalysis.
• * Palladium clusters are known for their catalytic properties, but their oxidation behavior requires further investigation.
• * Low-temperature oxidation of carbon monoxide (CO) is an important industrial process.

Purpose of the Study:

• * To synthesize and characterize palladium oxide clusters.
• * To investigate the catalytic activity of palladium oxide clusters in CO oxidation.
• * To elucidate the reaction mechanism of CO oxidation on palladium oxide clusters at a molecular level.

Main Methods:

• * Reaction of bare palladium clusters (Pd(n)(+)) with molecular oxygen (O(2)) in an octopole ion trap.
• * Multicollision conditions to promote cluster oxidation.
• * Gas-phase reaction kinetics measurements.
• * First-principles calculations to model reaction pathways.

Main Results:

• * Formation of a stable palladium oxide cluster, Pd(6)O(4)(+), as the sole product from Pd(6)(+) and O(2).
• * Pd(6)O(4)(+) exhibits resistance to further oxidation and stability, even fragmenting Pd(7)(+) upon reaction with O(2).
• * Pd(6)O(4)(+) acts as a catalytically active species, facilitating low-temperature CO oxidation in O(2)/CO mixtures.

Conclusions:

• * The synthesized Pd(6)O(4)(+) nano-oxide cluster is exceptionally stable.
• * This cluster demonstrates significant catalytic activity for CO oxidation at low temperatures.
• * The study provides molecular-level insights into the catalytic combustion cycle of CO on nano-oxide clusters.