Solid state preparation of NiO-CeO2 catalyst for NO reduction

Abstract

The development of efficient method for preparation of well-performed catalyst is an attractive topic in heterogeneous catalysis. Conventional route to obtaining mixed oxide catalysts is based on wet chemical methods. In the present study, a novel solid state method was proposed to fabricate NiO-CeO2 catalyst by directly mixing metal precursors (nickel nitrate hydrate and cerium nitrate hydrate) and the subsequent calcination, omitting the common drying procedure in wet preparations. The preparation process was tracked by thermogravimetry-differential thermal analysis (TG-DTA) and obtained catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 physisorption, powder X-ray diffraction (XRD), Raman spectroscopy, H2 temperature programmed reduction (H2-TPR) and tested in the model reaction of NO reduction by CO. Results showed that simultaneous decomposition of the mixed nitrates was occurred, suggesting cooperative interaction between the precursors. Moreover, in comparison with wet impregnation method, the catalyst from solid state preparation displayed not only improved textual properties (larger surface area and enriched porous structure), but also enhanced interfacial interactions between nickel and ceria, which promoted the bulk doping, surface dispersion of nickel species and the reduction of surface oxygen species. As a result, the catalytic performance in NO+CO reaction was significantly upgraded. Based on the preliminary results of this study, it is supposed the solid state preparation may open a convenient and versatile pathway to fabricate mixed oxide catalysts.