Research Of The Interaction Between PM And Strontium Doped Ceria-zirconia Solid Solution

Automotive exhaust is the main source of air pollution now. Generally engine modification and after-treatment control technique are used for this problem, and setting three-way-catalyst, one of after-treatment control, is the most effective solution. At present, the hot issues about three-way-catalyst include improving cold-start performance, reducing noble metal dosage and prolonging the used life.Pd, Pt and Rh played the important role in TWC application; Pd and Pt have influence on HC and CO oxidation, whereas Rh has effects on NOx reduction. As we known, HC, CO and NOx can reach the best conversion around the A/F=14.6. For the redox couple of Ce³⁺/Ce⁴⁺, Ceria-zirconia mixed oxides was used to accommodate the fluctuation of A/F around the 14.6 which storage oxygen when lean fuel condition and release oxygen when rich fuel condition, resulting in best conversion efficiency of HC, CO and NOx. The research of the interaction between the PM and CZ in application, resulting in changing in catalytic activity and OSC performance is ofimportant influence. In this paper, Sr doping samples Ce_0.67Zr_0.33Sr_xO_2+x (CZS_x) were prepared by sol-gel method and aged under H2O/air condition as the aged samples. PM (Pd, Rh) loaded on fresh and aged CZS samples were prepared by impregnation. Both fresh and aged samples were characterized on home-made dynamic OSC measure instrument and TWC measure equipment for their dynamic OSC and TWC performance. Structure analysis were also done by Brunnauer-Emmett-Teller (BET), X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS)and high resolution transmission electron microscopy(HRTEM).OSC results show that the oxygen storage capacity is enhanced by Sr²⁺ doping. However, after supporting Pd or Rh, undoped CZ shows higher dynamic OSC of CZ than Sr-doped samples, which may be ascribed to the SMSI effect. Sr doping can efficiently promote the catalytic activities, especially for PM supported on aged samples.Pd/aged CZS5 and Rh/aged CZS5 exhibit good performance indicating potential in practical applications.