In situ DRIFTs investigation of the reaction mechanism over MnOx-MOy/Ce0.75Zr0.25O2 (M = Fe, Co, Ni, Cu) for the selective catalytic reduction of NOx with NH3

Abstract A series of MnO x -MO y /Ce 0.75 Zr 0.25 O 2 (M = Fe, Co, Ni, Cu) catalysts were synthesized by an impregnation method and used for selective catalytic reduction (SCR) of NO x with NH 3 . The catalytic performances of various MnO x -MO y /Ce 0.75 Zr 0.25 O 2 catalysts were studied. It was found that MnO x -FeO y /Ce 0.75 Zr 0.25 O 2 catalyst showed excellent low-temperature activity and a broad temperature window. The catalysts were characterized by N 2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). Characterization of the catalyst confirmed the addition of iron oxide can enhance the NO oxidation ability of the catalyst which results in the outstanding low-temperature SCR activity. Meanwhile, iron oxides were well dispersed on catalyst surface which could avoid the agglomeration of active species, contributing to the strong interaction between active species and the support. More importantly, in situ DRIFTS results confirmed that bidentate nitrates are general active species on these catalysts, whereas the reactivity of gaseous NO 2 and bridged nitrates got improved because of the addition of Fe.