The role of rare earth elements in three-way catalysts: Implications for automobile emission control

This work characterizes Rare Earth Elements (REEs) behavior in three-way catalytic converters (TWCCs) at different degrees of on-road ageing. TWCCs are essential devices for preventing toxic gaseous emissions into the environment. TWCC has a washcoat with nanoparticles (NPs) of REEs doped CeO₂-ZrO₂, serving as a platinoid substrate. The essential function of the washcoat is to store oxygen for redox conversion reactions at high temperatures. To contribute to understanding washcoat ageing and further release of NPs, we characterize TWCCs by inductively coupled plasma mass spectrometry, Raman microspectroscopy, photoluminescence, and thermoluminescence techniques. The results suggest a decrease of La, Nd, Pr, and the redistribution of Ce-Zr cations in the crystal structure. We used transmission electron microscopy and dynamic light scattering to observe the growth of the NPs in the washcoat. The particle diameter increase from 102 to 202 nm may be associated with the decrease of these critical elements, which affects the efficiency/durability of these devices.