Formation of partial κ-Ce2Zr2O8 phase and its promotion on the supported Pd-only three-way catalysts

Abstract Severe air pollution is pushing towards developing more efficient three-way catalysts (TWCs), especially for the elimination of NO and C3H8. In this work, the highly active κ-Ce2Zr2O8 phase was investigated and introduced into TWCs. First, we demonstrated that the cation-ordered pyrochlore-type structure was formed during severe reduction, accompanied by a Zr-rich surface as detected by CH3OH-FTIR. Although only partial κ-Ce2Zr2O8 nano-domains were observed by HRTEM, which nucleated within the fluorite matrix of CZ-950RO, they acted as a blasting fuse to boost the whole reduction. Moreover, the presence of κ-Ce2Zr2O8 phase strengthened Pd-CZ interaction, providing a route to generate highly reactive Pdδ+ (δ ≥ 3) and immobilize palladium nanoparticles through Pd-O-Ce bonds as evidenced by XPS and CO chemisorption. Thanks to the strengthened Pd-CZ interaction, Pd/950RO exhibited a stable activity toward NO and C3H8 conversion.