CO Oxidation Promoted by NO Adsorption on RhMn₂O₃^- Cluster Anions

CO oxidation represents an important model reaction in the gas phase to provide a clear structure-reactivity relationship in related heterogeneous catalysis. Herein, in combination with mass spectrometry experiments and quantum-chemical calculations, we identified that the RhMn₂O₃^- cluster cannot oxidize CO into gas-phase CO₂ at room temperature, while the NO preadsorbed products RhMn₂O₃^-[(NO)_1,2] are highly reactive in CO oxidation. This discovery is helpful to get a fundamental understanding on the reaction behavior in real-world three-way catalytic conditions where different kinds of reactants coexist. Theoretical calculations were performed to rationalize the crucial roles of preadsorbed NO where the strongly attached NO on the Rh atom can greatly stabilize the products RhMn₂O₂^-[(NO)_1,2] during CO oxidation and at the same time works together with the Rh atom to store electrons that stay originally in the attached CO₂^- unit. The leading result is that the desorption of CO₂, which is the rate-determining step of CO oxidation by RhMn₂O₃^-, can be greatly facilitated on the reactions of RhMn₂O₃^-[(NO)_1,2] with CO.