The Role of Alkali Metal in α‐MnO 2 Catalyzed Ammonia‐Selective Catalysis

The unexpected phenomenon and mechanism of the alkali metal involved NH 3 selective catalysis are reported. Incorporation of K + (4.22 wt %) in the tunnels of α‐MnO 2 greatly improved its activity at low temperature (50–200 °C, 100 % conversion of NO x vs. 50.6 % conversion over pristine α‐MnO 2 at 150 °C). Experiment and theory demonstrated the atomic role of incorporated K + in α‐MnO 2 . Results showed that K + in the tunnels could form a stable coordination with eight nearby Osp3atoms. The columbic interaction between the trapped K + and O atoms can rearrange the charge population of nearby Mn and O atoms, thus making the topmost five‐coordinated unsaturated Mn cations (Mn 5c , the Lewis acid sites) more positive. Therefore, the more positively charged Mn 5c can better chemically adsorb and activate the NH 3 molecules compared with its pristine counterpart, which is crucial for subsequent reactions.