Effect of lauric acid on the grain growth of CeO2-ZrO2-Y2O3-La2O3 in different periods

Abstract

CeO2-ZrO2 based nanomaterials (CZ), as an oxygen buffer and noble metal support, have been widely used in three-way catalysts of exhaust gas purification due to unique oxygen storage/release c apacity. Surfactants are often utilized to modify the properties of CZ during the preparation. In this paper, four kinds of CeO2-ZrO2-Y2O3-La2O3 solid solutions were prepared by co-precipitation, and the effects of adding surfactant lauric acid at different stages of grain growth on the properties of the materials were analyzed by correlation characterization. The results show that the addition of lauric acid at the end of grain growth had no effect on the grain growth, but only modified the grain stacking mode, thus enhancing the thermal stability of CZ. However, the lauric acid added at the nucleation and growth stage of grain growth tends to selectively adsorb on the unstable (200) and (220) planes, forming an adsorption layer that inhibits the growth of the planes, which results in anisotropic growth of the (111) plane. Thus, more (200) and (220) planes are exposed, which contributes well to the formation of oxygen vacancies to the largest extent, especially in the nucleation stage. Consequently, the reduction temperature of the fresh sample was decreased by about 160 °C and 140 °C compared with no lauric acid and the addition of lauric acid at the end of grain growth, respectively, which exhibits excellent Pd-only three-way catalytic activity.