Asymmetric Coordination of Single-Atom Ru Sites Achieves Efficient N(sp³)–H Dehydrogenation Catalysis for Ammonia Oxidation

Abstract

Ruthenium single-atom catalysts have great potential in ammonia-selective catalytic oxidation (NH 3 −SCO); however, the stable sp 3 hybrid orbital of NH 3 molecules makes N(sp 3 )−H dissociation a challenge for conventional symmetrical metallic oxide catalysts. Herein, we propose a heterogeneous interface reverse atom capture strategy to construct Ru with unique asymmetric Ru 1 N 2 O 1 coordination. Ru 1 N 2 O 1 /CeO 2 exhibits intrinsic low-temperature conversion (T 100 at 160 °C) compared to symmetric coordinated Ru-based (280 °C), Ir-based (220 °C), and Pt-based (200 °C) catalysts, and the TOF is 65.4 times that of Ag-based catalysts. The experimental and theoretical studies show that there is a strong d−p orbital interaction between Ru and N atoms, which not only enhances the adsorption of ammonia at the Ru 1 N 2 O 1 position but also optimizes the electronic configuration of Ru. Furthermore, the affinity of Ru 1 N 2 O 1 /CeO 2 to water is significantly weaker than that of conventional catalysts (the binding energy of the Pd 3 Au 1 catalyst is −1.19 eV, but it is −0.39 eV for our material), so it has excellent water resistance. Finally, the N(sp 3 )−H activation of NH 3 requires the assistance of surface reactive oxygen species, but we found that asymmetric Ru 1 N 2 O 1 can directly activate the N(sp 3 )−H bond without the involvement of surface reactive oxygen species. This study provides a novel principle for the rational design of the proximal coordination of active sites to achieve its optimal catalytic activity in single-atom catalysis.