Catalytic activity of CeO 2–ZrO 2 mixed oxide catalysts prepared via sol–gel technique: CO oxidation

Abstract

CeO 2–ZrO 2 mixed oxide catalysts were prepared via a sol–gel technique and tested for carbon monoxide (CO) oxidation. Highly uniform nano-size solid solution particles of ceria–zirconia were attained under the conditions of this study (ca 100°C). The stabilization of the surface areas of the catalysts can be achieved by the addition of zirconium. The CO oxidation activity of the mixed oxides was found to be dependent on Ce/Zr ratio, which relates to the degree of reducibility. The catalytic activity for CO oxidation decreases with a decrease in Ce/Zr ratio. This might be due to the difference in phase compositions of the mixed oxides. It can be postulated that the cubic phase, fluorite structure, which is mainly found in Ce 1− x Zr x O 2 (where x<0.5) could be reduced easily than the tetragonal phase found in Ce 1− x Zr x O 2 (where x>0.5). Among the mixed oxide catalysts, Ce 0.75Zr 0.25O 2 was reported to exhibit the highest activity for CO oxidation.