Probing the role of nanoconfinement in improving N2 selectivity of Mn-based catalysts during NH3-SCR

Mn-based catalysts are promising low-temperature NH3-SCR catalysts, yet their strong oxidative capability leads to excessive N2O production, contributing to global warming. This study explored titanium nanotubes supported MnOx catalysts for NH3-SCR. The optimal catalyst, 10%Mn/TN showed remarkable NOx conversion over 95 % at 150-400 degrees C, together with a N-2 selectivity surpassing 95 % below 300 degrees C. In contrast, 10%Mn/Ti catalyst used for comparison had a N-2 selectivity as low as 30 %. The active Mn species may predominantly locate within the inner regions of the titanium nanotubes, which effectively regulated the redox properties of 10%Mn/TN. Density Functional Theory (DFT) calculations showed that the decomposition of NH4NO3 formed on 10%Mn/TN into H2O and N2O was more difficult than that on 10%Mn/Ti. Furthermore, the NH3-SCR reaction on 10%Mn/TN mainly followed the Eley-Rideal mechanism and NH4NO3 decomposition was effectively inhibited, consequently leading to a significant improvement in N-2 selectivity. These findings offer crucial insights for the design and development of Mn-based catalysts with superior activity and N-2 selectivity in NH3-SCR applications.