Size-dependent catalytic reactivity of NO Reduction by CO mediated by the RhnV2O3– clusters (n = 2–5)

Abstract

A fundamental understanding on the precise structural characteristic of interface active sites confined in heterogeneous catalysts is pivotal to construct vigorous metal–support boundary. Herein, a series of RhnV2O3–5– (n = 2–5) clusters were theoretically designed and we demonstrated that RhnV2O3–5– can catalytically reduce NO into N2 selectively by CO. We identified that the structure of RhnV2O3− can be considered as the dispersion of a Rhn moiety on the V2O3 “support” anchored by two V atoms. The distance between the top Rh atom that is responsible for reactant capture and V atom in RhnV2O3– becomes longer with the increase of cluster size, and the leading result is that V atoms in larger clusters can be less accessible during the reactions. A size-dependent behavior of NO reduction by RhnV2O3− was observed that V atom always be involved in the triatomic site RhV2 or Rh2V in Rh2−4V2O3− to drive N−O rupture and N−N coupling, while only three Rh atoms in Rh5V2O3− are available to drive NO reduction. One Rh atom in products Rh2−4V2O4,5− also functions as the anchoring site for CO and then delivers CO for oxidation by nearby coordinated oxygen atom. This finding emphasizes that our recently identified triatomic active site Ceδ+–Rhδ––Ceδ+ in RhCe2O3− for selective reduction of NO into N2 still prevails but could behave in different manners in larger RhnV2O3− (n ≥ 5) clusters.