Moderating the interaction among Pd, CeO₂, and Al₂O₃ for improved three-way catalysts

Area of Science:

• Materials Science
• Catalysis
• Environmental Science

Background:

• Commercial three-way catalysts rely on palladium (Pd) distribution and cerium dioxide (CeO₂)-aluminum oxide (Al₂O₃) interactions for optimal performance.
• Sufficient Pd doping into ceria-based oxides and intimate CeO₂-Al₂O₃ interaction generally benefit catalytic reactions.

Purpose of the Study:

• To investigate the impact of Pd distribution and CeO₂-Al₂O₃ interaction on the catalytic activity of PdCe/Al₂O₃ catalysts.
• To compare the performance of catalysts prepared via co-precipitation (PdCe/Al₂O₃-CP) versus impregnation (PdCe/Al₂O₃-Imp).

Main Methods:

• Synthesis of PdCe/Al₂O₃ catalysts using co-precipitation (CP) and impregnation (Imp) methods.
• Characterization of catalyst properties including Pd doping, CeO₂-Al₂O₃ interaction, Pd dispersion, surface area, pore structure, and redox properties.
• Evaluation of catalytic activity for C₃H₆, CO, and NO conversion.

Main Results:

• The PdCe/Al₂O₃-CP catalyst exhibited significantly higher catalytic activity (lower T50 for C₃H₆, CO, NO) compared to PdCe/Al₂O₃-Imp.
• PdCe/Al₂O₃-CP showed moderate Pd doping into CeO₂, resulting in a higher fraction of active metallic Pd (Pd⁰) and enhanced Pd dispersion.
• Less intimate CeO₂-Al₂O₃ interaction in PdCe/Al₂O₃-CP led to higher Pd dispersion, specific surface area, pore volume, and pore size.

Conclusions:

• Contrary to general expectations, moderate Pd doping and less intimate CeO₂-Al₂O₃ interaction enhance three-way catalytic activity.
• The improved performance of PdCe/Al₂O₃-CP is attributed to abundant reactive Pd⁰, accessible active sites, enhanced redox properties, and oxygen vacancies.
• Simultaneously optimizing Pd distribution and CeO₂-Al₂O₃ interaction in a single step offers a promising strategy for industrial catalyst development.