Catalytic reactions on neutral Rh oxide clusters more efficient than on neutral Rh clusters

Area of Science:

• Surface Science
• Catalysis
• Nanomaterials

Background:

• Gas phase catalytic reactions are crucial in industrial processes.
• Understanding molecular-level reaction mechanisms on metal clusters is key to designing efficient catalysts.
• Rhodium clusters are known catalysts for various reactions, but their size-dependent catalytic activity requires further investigation.

Purpose of the Study:

• To investigate the catalytic activity of isolated neutral rhodium clusters (Rh(n), n = 10-28) in gas-phase reactions.
• To elucidate the reaction mechanisms of nitrous oxide (N(2)O) reduction and carbon monoxide (CO) oxidation on rhodium clusters.
• To determine the influence of cluster size and oxidation state on catalytic efficiency.

Main Methods:

• Utilized mass spectrometry to observe gas-phase catalytic reactions at the molecular level.
• Monitored sequential oxygen transfer reactions during N(2)O reduction.
• Investigated oxygen extraction reactions by CO on oxidized rhodium clusters.

Main Results:

• Determined rate constants for N(2)O reduction as a function of rhodium cluster size (n = 10-28).
• Observed significantly higher rate constants (2-3 orders of magnitude) for oxygen extraction by CO on highly oxidized rhodium clusters (Rh(n)O(m), m ≥ 4) compared to less-oxidized clusters (m ≤ 3).
• Demonstrated that oxidized rhodium clusters are more efficient catalysts than bare or less-oxidized clusters.

Conclusions:

• Rhodium clusters exhibit size-dependent catalytic activity for N(2)O reduction and CO oxidation.
• Catalytic efficiency is enhanced in oxidized rhodium clusters, particularly when the reaction cycles involve Rh(n)O(m) with m ≥ 4.
• Oxidized rhodium clusters serve as more effective catalysts than non- or less-oxidized clusters, aligning with surface studies of CO oxidation on rhodium.