Novel Mn–Ce bi-oxides loaded on 3D monolithic nickel foam for low-temperature NH3-SCR de-NOx: Preparation optimization and reaction mechanism

This study explored the superior citrate method (CM) to synthesize Mn–Ce bi-oxides on 3D monolithic Ni-foam (NF) catalysts for the selective catalytic reduction of NO by NH3 (NH3-SCR). The 17 wt% Mn(7)Ce(3)Ox/NF (CM-17) catalyst shows the NOx conversion of 98.7% at 175 °C and 90% in the presence of 10 vol% H2O. It is revealed that the combination of surface-active oxygen (formed by high-level oxygen vacancies) and strongly oxidized Mn4+ species promots the Fast-SCR reactions, in which Mn4+ species play a leading role in NH3-SCR reaction, and the unsaturated Ni atoms and also Ce3+ species promote electron exchange and thus improve the redox performance. The coexistence mechanisms of Fast-SCR reactions and E-R pathways are observed over Mn-CeOx/NF catalyst, which may be promoted by the Brønsted sites at low temperature. In addition, the heat resistance, stability, 3D monolithic porous structure and excellent physical properties of foam nickel provide a unique growth substrates for catalysts preparation and reaction sites for NOx purification. Therefore, industrial application of Mn–Ce bi-oxides loaded on 3D monolithic is proposed to be achieved through reasonable preparation methods.