Fractional-hydrolysis-driven formation of nonuniform dopant concentration catalyst nanoparticles of Cr/CexZr1−xO2 and their catalysis in oxidation of NO

Abstract

Cr/ceria–zirconia solid solution (Cr/CexZr1−xO2) nanoparticles with nonuniform dopant concentration as NO oxidizing catalysts were prepared via a simple, low-cost method. The preparation process utilizes aqueous phase reactions which simplifies the experimental procedure, saves the cost and leads the Ce enriched on the surface of products. The impregnation method makes the Cr enriched on the surface of products which improves the efficiency of dopant. The physicochemical characteristics were investigated by various techniques namely, XRD, Raman, BET, TEM, XPS, NO (or O2)–TPD and UV–vis. The results demonstrated that Zr-rich sample with tetragonal structure was beneficial for the increasing of surface area and the decreasing of particle size and result in a higher adsorption capacity of NO and O2 than Ce-rich sample. Therefore, Cr/Ce0.14Zr0.86O2 catalyst exhibited the higher activity for NO oxidation than other catalysts, which achieved 62.18% at 300°C. The UV–vis analysis proved that the adsorbed NO interacted with the adsorbed O2, obeying L–H model. The dynamics tests confirmed the above suggestion.