Boosting the three-way catalytic reactions on Pd/CeO2-ZrO2-Al2O3 catalyst: The superior lanthanum-doping strategy

Disclosing the different structure–function relationship of promoters is vital for designing catalysts with superior performance. In this work, the dispersion and location of lanthanum (La), namely the interaction with CeO₂-ZrO₂ (CZ) component or Al₂O₃ component, has been regulated by controlling the pretreatment temperature of CeO₂-ZrO₂-Al₂O₃ (CZA) support, then the effects of La structure on Pd/CZA three-way catalyst have been systematically investigated to pick out the superior doping strategy. By XRD, BET and TEM tests, it has been found that although La interacted with Al₂O₃ is beneficial to suppress the phase transition of Al₂O₃ and increase the specific surface area of CZA materials, the formed LaAlO₃ also inhibits the transfer of oxygen species between CZ particles, which decreases the oxygen storage capacity (OSC) of the CZA and narrows the three-way operation window of the resulting Pd/CZA catalyst. On the contrary, La doping into CZ component significantly promotes the movement of oxygen species due to the increased surface oxygen vacancy (O_v), which widens the three-way operation window and stabilizes Pd in small particle size and high valence state. Meanwhile, the obtained Pd/CZA catalyst with more O_v weakens N-O bond, thus increasing the content of monodentate nitrate adsorbed on Pd and promoting the NO + C₃H₈ reaction. So, it shows excellent three-way catalytic activity. This facile doping strategy can be further extended to other composite oxide for specific catalytic applications.