Synergy of Single-Atom Fe₁ and Ce–O_v Sites on Mesoporous CeO₂–Al₂O₃ for Efficient Selective Catalytic Reduction of NO with CO

Abstract

Nonprecious transition-metal oxides, especially Fe-, Cu-, Co-, and Mn-containing mixed oxides, have been regarded as promising alternatives for noble metal catalysts for the abatement of NO x contamination. However, the identification of the real catalytically active sites for these mixed oxides remains unclear in most cases, which limits our in-depth understanding of the intrinsic mechanism. Here, we comprehensively investigated an iron− cerium−aluminum oxide (Fe 1 /CeO 2 −Al 2 O 3 ) prepared with a coprecipitation method. Structural identification confirmed that Fe sites are atomically dispersed, bonding with four O atoms in the first coordination shell and with two Ce atoms in the second shell on average. Highly efficient removal of NO with 100% selectivity toward N 2 has been achieved over these sites at a temperature as low as 250 °C. In situ characterizations and computational studies revealed that the high activity and N 2 selectivity of Fe 1 /CeO 2 − Al 2 O 3 can be attributed to the synergetic effect of the single-atomic Fe 1 site and surrounding Ce−O v , which intensively promotes the adsorption of NO molecules and N 2 O intermediates. Subsequently, Ce−O v facilitates the N−O dissociation toward N 2 and then is regenerated with CO, forming CO 2 as a product. The present results provide valuable insights into the mechanism of transitionmetal oxide catalysts for the NO−CO reaction and offer useful guidance for designing catalysts with high activity and selectivity.