Comparative study of moisture treatment Pd@CeO2/Al2O3 and Pd/CeO2/Al2O3 catalysts for automobile exhaust emission reactions: effect of core-shell interface

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 activ...