Core-shell Pd@CeO₂/γ-Al₂O₃ catalysts: Boosting efficiency and durability in stoichiometric natural gas vehicle exhaust treatment

Natural gas vehicles (NGVs) offer significant environmental advantages by reducing pollutant emissions, but effective exhaust treatment remains a challenge due to high methane emissions and catalyst deactivation over time. This study introduces a core-shell Pd@CeO₂/Al₂O₃ three-way catalyst (TWC) designed to enhance the efficiency and durability of NGV exhaust treatment. The core-shell structure significantly improves catalytic performance. The optimized Pd@Ce/Al (S-500) catalyst demonstrates excellent low-temperature activity, with T₅₀ values of 336 °C for CH₄ and 397 °C for NO. It also achieves remarkable reductions of 113 and 177 °C in the T₉₀ for CH₄ and NO conversion, respectively, compared to the non-core-shell counterpart, Pd-Ce/Al (S-500). Characterizations reveal enhanced metal-support interactions, increased oxygen vacancies, and optimized Pd-CeO₂ interfaces as key active sites. Density functional theory calculations further demonstrate that the core-shell structure facilitates electron transfer at Pd-CeO₂ interfaces and lowers energy barriers for three-way reactions, enhancing catalytic efficiency. Notably, the core-shell Pd@Ce/Al (S-500) catalyst maintains high conversion efficiency for CH₄ and NO, with only slight losses (5.5% and 6.6%, respectively) over a 100-h time-on-stream stability test, following 16 h of harsh hydrothermal aging at 800 °C, showcasing its long-term stability. These findings provide a deeper understanding of the role of the core-shell Pd@CeO₂ structure in Pd-based TWCs and offer valuable insights for designing durable and efficient catalysts to meet the stringent emission standards of NGVs.