Catalysis Today, Vol.339, 135-147, 2020
Effect of support preparation with different concentration precipitant on the NOx storage performance of Pt/BaO/CeO2 catalysts
In this study, the CeO2 nanorods as the supports of Pt/BaO/CeO2 catalysts were synthesis by the alkali-assisted hydrothermal method in a solution containing different content of NaOH. Pt/BaO/CeO2 catalyst with 7.5M NaOH pre-added in the support preparation process showed higher NOx storage capacity and NOx removal efficiency than samples derived from other concentration NaOH. Moreover, even under shorter rich time (3s) and more lean-rich cycles (60), Pt/BaO/CeO2-7.5M still maintained above 80% NOx conversion from 250 to 450 degrees C, exhibiting good fuel economy and durability. A series of characterization techniques including XRD, N-2-adsorption, TEM, XPS, Raman, H-2-TPR, and NO2-TPD were conducted to investigate the physical, chemical properties. Combining the activity with the structure of catalysts, a linear relationship between the NOx storage capacity (NSC) of NSR catalysts and the amount of oxygen vacancies was drawn. Meanwhile, the strong synergetic effect among Pt and CeO2 attributed to the role of oxygen vacancies in anchoring the active component Pt, promoting the mobility of surface oxygen species, was also related to the NSC value of NSR catalysts. These results indicated that the oxygen vacancies were responsible for the excellent catalytic activity.