A stable spherical MOF-derived Mnx-Fe2O3/C catalysts for low-temperature CO-SCR

Abstract

A series of spherical Mnx-Fe2O3/C catalysts derived from MnFe-MOF-74 were fabricated via a sacrificing template method and applied for CO-SCR. Among the tested catalysts, Mn0.5-Fe2O3/C catalysts achieved a maximum NO conversion of 100 % in a broad temperature range between 225 and 500 °C, significantly higher than monometallic Fe2O3/C. Based on TPR, BET and XPS results, a redox reaction Fe3+ + Mn2+ ↔ Fe2+ + Mn3+ over Fe-O-Mn sites was constructed, which greatly facilitated the adsorption and activation of NO molecules. DFT calculations revealed that the incorporation of Mn obviously increased the local electron density of Fe-Mn sites not only resulting in a strong C-Fe/Mn and N-Fe/Mn bonding, but also effectively weaken the N-O bond. And the NO adsorption energy of Fe-O-Mn site over Mn doped α-Fe2O3 is −0.87 eV which indicates the stability of the adsorption configuration. Combined with the in situ FT-IR results, important intermediates Fe2+-(NO)22– and N2O were identified respectively at 1261 and 1358 cm−1, which were promoted by the synergistic interaction of Mn and Fe. This Mn-Fe synergistic interaction could contribute to lowering reaction barrier and boosting CO-SCR performance.