Improved N 2 Selectivity of MnO x Catalysts for NO x Reduction by Engineering Bridged Mn 3+ Sites.

Mn-based catalysts are promising for selective catalytic reduction (SCR) of NO x with NH 3 at low temperatures due to their excellent redox capacity. However, the N 2 selectivity of Mn-based catalysts is an urgent problem for practical application owing to excessive oxidizability. To solve this issue, we report a Mn-based catalyst using amorphous ZrTiO x as the support (Mn/ZrTi-A) with both excellent low-temperature NO x conversion and N 2 selectivity. It is found that the amorphous structure of ZrTiO x modulates the metal-support interaction for anchoring the highly dispersed active MnO x species and constructs a uniquely bridged Mn 3+ bonded with the support through oxygen linked to Ti 4+ and Zr 4+ , respectively, which regulates the optimal oxidizability of the MnO x species. As a result, Mn/ZrTi-A is not conducive to the formation of ammonium nitrate that readily decomposes to N 2 O, thus further increasing N 2 selectivity. This work investigates the role of an amorphous support in promoting the N 2 selectivity of a manganese-based catalyst and sheds light on the design of efficient low-temperature deNO x catalysts.