Promotion of CeO2–ZrO2–Al2O3 composite by selective doping with barium and its supported Pd-only three-way catalyst

Abstract

In this work, CeO2–ZrO2–Al2O3 (CZA) composites promoted by selective doping with Ba were prepared by simple coprecipitation method. The structural characterization results reveal that with small doping amount (≤6wt%), Ba can preferentially combine with Al2O3 and acts as a stabilizer, which could facilitate the formation of more homogeneous CZ solid solutions. When the content of BaO increases to 8wt%, besides the portion combined with Al2O3, the remnant Ba would enter into the lattice of CeO2–ZrO2 to form a ternary CeO2–ZrO2–BaO solid solution, thus further improved oxygen mobility is obtained. However, excessive doping amount (10wt%) brings about self-aggregation of BaO, which seriously deteriorates the structure of the CeO2–ZrO2–Al2O3-BaO composite. The XPS results demonstrate that with optimal doping content of BaO (8wt%), the supported catalyst Pd/CZAB8 possesses highest surface Pd and Ce3+ concentrations, which consequently leads to improved reducibility and catalytic performance. Furthermore, the synergistic effect between CeO2–ZrO2–BaO and BaO–Al2O3 helps improve the thermal stability of Pd/CZAB8. Thus, superior textural, structural, morphological and reduction properties along with enhanced three-way catalytic performance are obtained for aged Pd/CZAB8a.