Improved N2 Selectivity of MnO x Catalysts for NO x Reduction by Engineering Bridged Mn3+ Sites

Mn-basedcatalysts are promising for selective catalytic reduction(SCR) of NO x with NH3 at lowtemperatures due to their excellent redox capacity. However, the N-2 selectivity of Mn-based catalysts is an urgent problem forpractical application owing to excessive oxidizability. To solve thisissue, we report a Mn-based catalyst using amorphous ZrTiO x as the support (Mn/ZrTi-A) with both excellent low-temperatureNO( x ) conversion and N-2 selectivity.It is found that the amorphous structure of ZrTiO x modulates the metal-support interaction for anchoringthe highly dispersed active MnO x speciesand constructs a uniquely bridged Mn3+ bonded with thesupport through oxygen linked to Ti4+ and Zr4+, respectively, which regulates the optimal oxidizability of theMnO( x ) species. As a result, Mn/ZrTi-A isnot conducive to the formation of ammonium nitrate that readily decomposesto N2O, thus further increasing N-2 selectivity.This work investigates the role of an amorphous support in promotingthe N-2 selectivity of a manganese-based catalyst and shedslight on the design of efficient low-temperature deNO( x ) catalysts.