Optimization of platinum group metal–nickel composites as thermally stable low-temperature light-off three-way catalysts

Reducing the reliance on Pt group metals (PGMs) while enhancing the efficiency of three-way catalysts (TWCs) is a critical goal for emission control in modern hybrid engines. In this study, composite catalysts of Ni supported on ceria (Ni/CeO₂) and Pt–Pd supported on ceria–zirconia mixed oxide (PtPd/CZ) were systematically investigated to maximize their synergy and minimize unfavorable interactions. After thermal aging at 800 °C under constant fuel-lean condition (L aging), a composite of PtPd/CZ and Ni/CeO₂ in a 1:1 wt ratio exhibited superior low-temperature light-off TWC performance to that of PtPd/CZ alone, despite containing 50 % less PGMs. The preparations of composite catalysts in powder and honeycomb forms suggested that the synergistic effect of the components may be attributed to a high metal dispersion and synergistic interactions due to the optimal proximity between PtPd/CZ and Ni/CeO₂ during L aging. By contrast, the intimate contact between PGMs and the CeO₂ surface overstabilized the PGM oxides, decreasing the activity. The positive interactions of the present composite catalyst were less obvious after thermal aging under stoichiometric–lean–rich fluctuating cycles because of PGM sintering. Overall, this study represents a significant advancement in PGM–Ni composite catalysts, paving the way toward more efficient and cost-effective TWC systems for next-generation hybrid engines.