| Increasing strict regulations for automotive exhaust emission control inevitably demand advanced technologies in three-way catalysts (TWC). The complexity of vehicle operation conditions not only requires high catalytic efficiency of TWCs at stoichiometric air-fuel ratio, but also needs being compatible for application under wider air-fuel ratios. This thesis aims to investigate the doping effect of alkaline earth metals (Ca, Sr, Ba), steam in net reaction and hydrothermal ageing for model Pd/Ce0.67Zr0.33-Al2O3 TWCs.Alkaline earth metals doped Pd/MCe0.67Zr0.33O2-Al2O3 (M=Ca, Sr, Ba) were synthesized by a citric acid sol-gel method. TWC, dynamic oxygen storage capability (OSC) tests were performed to evaluate the catalytic redox activities. Contributions from texture modifications were obtained from XRD and BET analysis.Research result reveals that all as prepared samples maintained as fine particles with less crystallization and desirable thermal stability. Due to the optimized bulk and surface texture, phase separation did not take place for ceria-zirconia (CZ) solid solutions after hydrothermal ageing at 1050℃for 10 h, in conjecture with the unchanged 0.125λ-windows'width. Injection of steam in the TWC operating atmosphere promoted the water gas shift (WGS) reaction, and therefore facilitating widen theλ-windows to further extent. Doped alkaline earth metals profoundly influence the catalysts'texture and activity in discrepant ways.①Ca dopants entered the lattice of alumina and depressed the sintering of the latter, without significant effects for the width ofλ-window;②Besides entering alumina lattice, Sr dopants also worked for the lattice of CZ, fueling CO and NOx conversion in lean condition. It is estimated that 3% doped Sr has the optimized effect for widenλ-windows;③Ba dopants affected the structure of CZ in elevating thermal stability and promoting NOx conversion in lean conditions, thus broadening theλ-windows.Width ofλ-windows is of less correlation with the surface areas of TWCs. Instead, higher OSC activity of TWCs is of critical and positive role for widening theλ-windows.
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