Promotional Effect of Preparation Methods on Catalytic Reduction of NO by CO over CoCeO_x Catalysts

In this study, a series of CoCeO_x catalysts were prepared by template, solid-state grinding with cobalt sulfate or cobalt acetate as the precursor and the oil bath method for catalytic reduction of NO_x by CO (CO–NO). These catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction of H₂, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results indicated that CoCeO_x-TA and CoCeO_x-SS catalysts exhibited much higher activity, which were attributed to excellent reducibility property, abundant chemical adsorbed oxygen, and NO absorption sites. In the presence of O₂, the activity decreased obviously over CoCeO_x-TA, CoCeO_x-SS, and CoCeO_x-SA catalysts. However, the activity increased at high temperatures over the CoCeO_x-OA catalyst. According to the result of in situ DRIFTS, nitrate species decreased over CoCeO_x-TA, CoCeO_x-SS, and CoCeO_x-SA catalysts in the presence of O₂, which might inhibit the reduction efficiency of NO. Moreover, NO adsorption was not affected by O₂ over CoCeO_x-OA catalyst, which could contribute to its high activity in the CO-selective catalytic reduction reaction.