Boosting N₂ Selectivity of Catalytic NO Reduction via Single-Atom Engineered MTaO₃– (M = Cu, Al, V, Ti, Nb, and Ce) Clusters

Catalytic reduction of NO to N₂ is crucial to meeting the stringent emission regulations and the rising atmospheric N₂O level, while the structural determinants of N₂ selectivity remain elusive. Herein, benefiting from state-of-the-art mass spectrometry, we demonstrated that copper–tantalum oxide clusters CuTaO_3–5^– can catalyze NO reduction by CO to generate N₂O and N₂. Quantum-chemical calculations identified that the ONNO dimer on CuTaO₃^– branches into two competitive pathways and the weak Cu–O bond suppresses N₂ formation. Guided by this insight, we theoretically designed a series of clusters MTaO₃^– (M = Al, V, Ti, Nb, and Ce) with stronger M–O bonds and the improved N₂ selectivity on AlTaO₃^– was verified by mass spectrometry experiments. Moreover, a previously overlooked N₂ generation pathway was experimentally discovered where an N^• radical formed by NO homolysis on MTaO₃^– (M ≠ Cu and Al) couples with another NO. The potential of these single-atom engineered MTaO₃^– clusters for selective NO reduction by CO was rationalized, and scientific guidance to develop advanced catalysts was proposed.