Correlation of Physicochemical Characteristics of CoOx Supported by a CeO2 Nanorod with NO Removal by CO

Abstract

In this study, cobalt oxides were loaded on a CeO2 nanorod and synthesized using a hydrothermal method and wet impregnation to reduce nitrogen monoxide (NO) by carbon monoxide (CO). A series of catalysts were characterized by nitrogen physisorption, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray spectroscopy (XPS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to determine the reacting path in the reduction zones. Co species were highly dispersed on the CeO2 nanorod when the precursor solution content was less than 20% by weight. Co3+ species were the most active components in the NO+CO reaction, and the Co3+ fraction reached a maximum when the precursor concentration was 10% by weight. A possible mechanism for the CO+NO reaction was suggested in which NO adsorbs onto the surface of CoOx−CeO2 and transforms to some nitrite/nitrate species under the reacting condition. At lower temperature (<300°C), adsorbed CO species react with a nitro complex to generate N2O and CO2, whereas as the temperature increases, these nitro complexes transform to coordinate nitrates reacting with CO species to generate nontoxic N2 and CO2.