Mechanistic Insight into the Promotion of the Low-Temperature NH<sub>3</sub>-Selective Catalytic Reduction Activity over Mn<sub><i>x</i></sub>Ce<sub>1–<i>x</i></sub>O<sub><i>y</i></sub> Catalysts: A Combined Experimental and Density Functional Theory Study
Maofan Li, Meng Gao, Guangzhi He, Yunbo Yu, Hong He
Abstract
CeO 2 has attracted much attention in the field of selective catalytic reduction of NO with NH 3 (NH 3 -SCR). However, poor low-temperature activity and a narrow operation window restrict the industrial application of Ce-based oxide catalysts. Herein, the low-temperature NH 3 -SCR activity of Ce-based oxide catalysts was dramatically improved by Mn doping, and the mechanism was elucidated at the atomic level by experimental measurements and density functional theory calculations. We found that the addition of Mn significantly promoted the formation of surface oxygen vacancies. The oxygen vacancies easily captured O 2 in air and formed active oxygen species (superoxide and peroxide) on the surface. The surface active oxygen species efficiently oxidized NO into NO 2 and then facilitated the “fast SCR” reaction. This study provides atomic-level insights into the promotion of the NH 3 -SCR activity over Mn–Ce composite oxides and is beneficial for the development of low-temperature Ce-based catalysts.