New Insights into the Role of Nd in CeO2–ZrO2–Al2O3 Composite and Supported Pd Catalyst

Abstract

To improve the performance of CeO₂–ZrO₂–Al₂O₃ (CZA) composite, Nd was introduced and the role of Nd was deeply investigated. The characterization results revealed that introduction of appropriate amount of Nd (4 wt %) can effectively modify the textural and structural properties of CZA, in this case, Nd selectively combines with CZ and hardly interacts with Al₂O₃, which could incorporate into the lattice of CZ to form ternary CeO₂–ZrO₂–Nd₂O₃ (CZN) solid solution, thus more lattice defects and improved oxygen mobility are obtained. However, excessive doping amount of Nd (6–8 wt %) brings about formation of Nd_0.5Ce_0.5O_1.75 and phase separation of CZ especially after thermal aging treatment. The XPS results demonstrate that the supported catalyst Pd/CZAN4 possesses higher surface Pd and Ce³⁺ concentrations compared with Pd/CZA, which consequently leads to improved reducibility and catalytic performance. Furthermore, higher thermal stability is obtained, after aging treatment, Pd/CZAN4a still exhibits enhanced reduction property along with superior three-way catalytic performance.