Factors Determining the Selectivity of NO Reduction Catalyzed by Copper-Vanadium Oxide Cluster Anions Cu2VO3-5.

Abstract

Catalytic NO reduction by CO is imperative to satisfy the increasingly rigorous emission regulations. Identifying the structural characteristic of crucial intermediate that governs the selectivity of NO reduction is pivotal to having a fundamental understanding on real-life catalysis. Herein, benefiting from the state-of-the-art mass spectrometry, we demonstrated experimentally that the Cu₂VO_3-5 ^- clusters can mediate the catalysis of NO reduction by CO, and two competitive channels to generate N₂O and N₂ can co-exist. Quantum-chemical calculations were performed to rationalize this selectivity. The formation of the ONNO unit on the Cu₂ dimer was demonstrated to be a precursor from which two pathways of NO reduction start to emerge. In the pathway of N₂O generation, only the Cu₂ dimer was oxidized and the VO₃ moiety functions as a "support", while both moieties have to contribute to anchor oxygen atoms from the ONNO unit and then N₂ can be generated. This finding displays a clear picture to elucidate how and why the involvement of VO₃ "support" can regulate the selectivity of NO reduction.