Novel Mn–Ce bi-oxides loaded on 3D monolithic nickel foam for low-temperature NH3-SCR de-NO : 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 NH 3 (NH 3 -SCR). The 17 wt% Mn(7)Ce(3)O x /NF (CM-17) catalyst shows the NO x conversion of 98.7% at 175 °C and 90% in the presence of 10 vol% H 2 O. It is revealed that the combination of surface-active oxygen (formed by high-level oxygen vacancies) and strongly oxidized Mn 4+ species promots the Fast-SCR reactions, in which Mn 4+ species play a leading role in NH 3 -SCR reaction, and the unsaturated Ni atoms and also Ce 3+ 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-CeO x /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 NO x purification. Therefore, industrial application of Mn–Ce bi-oxides loaded on 3D monolithic is proposed to be achieved through reasonable preparation methods. MnCeO x active component relies on the good 3D porous structure of nickel foam, and the efficient purification of NO x was realized under the synergizing effect of Fast-SCR and E-R mechanism. • NO-to-NO 2 oxidation was enhanced by oxygen vacancies with the increased Ce 3+ -content. • Redox ability was promoted by the synergistic effect of unsaturated Ni-atoms with Mn and Ce sites. • Eley-Rideal and Fast-SCR mechanisms were promoted over Mn-CeO x /NF via Brønsted sites-adsorbed NH 4 + species.