Comparative Study of Moisture-Treated Pd@CeO₂/Al₂O₃ and Pd/CeO₂/Al₂O₃ Catalysts for Automobile Exhaust Emission...

In this article, moisture-treated Pd@CeO₂/Al₂O₃ and Pd/CeO₂/Al₂O₃ catalysts were synthesized and applied in automotive three-way catalytic (TWC) reactions. Compared to the Pd/CeO₂/Al₂O₃ catalyst, the Pd@CeO₂/Al₂O₃ core-shell catalyst had better TWC activities. Transmission electron microscopy (TEM) images and X-ray photoelectron spectra (XPS) showed excess PdO₂ on the Pd and CeO₂ interface of Pd@CeO₂ nanoparticles. Fourier transform infrared (FT-IR) spectra analysis demonstrated the generation of the hydroperoxyl (*OOH) groups on the surface of the Pd@CeO₂ nanoparticle. CO-diffuse reflectance Fourier transform (DRIFT) measurement suggested that the CO adsorbed on *OOH species contributed to the formation of CO₂ and intermediate *COOH. NO-DRIFT results showed that more *NO₂ species appeared on the moisture-treated Pd@CeO₂ nanoparticle, which was the main active site in the automobile TWC reaction. These were the main factors contributing to the moisture-treated Pd@CeO₂/Al₂O₃ catalyst's high catalytic activities. The collected data revealed the crucial role of the co-promoting effect of moisture and core-shell interface on TWC reactions over the Pd@CeO₂/Al₂O₃ catalyst, which could be applied to other catalytic reactions.