Highly Active and Durable Rh-Mo-Based Catalyst for the NO-CO-C₃H₆-O₂ Reaction Prepared by Using Hybrid Clustering

We developed a method for preparing catalysts by using hybrid clustering to form a high density of metal/oxide interfacial active sites. A Rh-Mo hybrid clustering catalyst was prepared by using a hybrid cluster, [(RhCp*)₄Mo₄O₁₆] (Cp* = η⁵-C₅Me₅), as the precursor. The activities of the Rh-Mo catalysts toward the NO-CO-C₃H₆-O₂ reaction depended on the mixing method (hybrid clustering > coimpregnation ≈ pristine Rh). The hybrid clustering catalyst also exhibited high durability against thermal aging at 1273 K in air. The activity and durability were attributed to the formation of a high-density of Rh/MoO interfacial sites. The NO reduction mechanism on the hybrid clustering catalyst was different from that on typical Rh catalysts, where the key step is the N-O cleavage of adsorbed NO. The reducibility of the Rh/MoO interfacial sites contributed to the partial oxidation of C₃H₆ to form acetate species, which reacted with NO+O₂ to form N₂ via the adsorbed NCO species. The formation of reduced Rh on Rh₄Mo₄/Al₂O₃ was not as essential as that on typical Rh catalysts; this explained the improvement in durability.