Synergistic Effects of Ternary PdO–CeO₂–OMS-2 Catalyst Afford High Catalytic Performance and Stability in the Reduction of NO with CO

Abstract

We developed a robust ternary PdO-CeO₂-OMS-2 catalyst with excellent catalytic performance in the selective reduction of NO with CO using a strategy based on combining components that synergistically interact leading to an effective abatement of these toxic gases. The catalyst affords 100% selectivity to N₂ at the nearly full conversion of NO and CO at 250 °C, high stability in the presence of H₂O, and a remarkable SO₂ tolerance. To unravel the origin of the excellent catalytic performance, the structural and chemical properties of the PdO-CeO₂-OMS-2 nanocomposite were analyzed in the as-prepared and used state of the catalyst, employing a series of pertinent characterization methods and specific catalytic tests. The experimental as well as theoretical results, based on density-functional theory calculations suggest that CO and NO follow different reaction pathways, CO is preferentially adsorbed and oxidized at Pd sites (Pd^II and Pd⁰), while NO decomposes on the ceria surface. Lattice oxygen vacancies at the interfacial perimeter of PdO-CeO₂ and PdO-OMS-2, and the diffusion of oxygen and oxygen vacancies are proposed to play a critical role in this multicenter reaction system.