Superior Oxidative Dehydrogenation Performance toward NH 3 Determines the Excellent Low-Temperature NH 3 -SCR Activity of Mn-Based Catalysts

Mn-based oxides exhibit outstanding low-temperature activity for the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) compared with other catalysts. However, the underlying principle responsible for the excellent low-temperature activity is not yet clear. Here, the atomic-level mechanism and activity-limiting factor in the NH 3 -SCR process over Mn-, Fe-, and Ce-based oxide catalysts are elucidated by a combination of first-principles calculations and experimental measurements. We found that the superior oxidative dehydrogenation performance toward NH 3 of Mn-based catalysts reduces the energy barriers for the activation of NH 3 and the formation of the key intermediate NH 2 NO, which is the rate-determining step in NH 3 -SCR over these oxide catalysts. The findings of this study advance the understanding of the working principle of Mn-based SCR catalysts and provide a fundamental basis for the development of future generation SCR catalysts with excellent low-temperature activity.