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 ℃ 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 Brφnsted 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 cat-alysts 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.