Core-shell catalyst improves exhaust treatment efficiency and durability for NGVs

Natural gas vehicles (NGVs) offer a promising path toward cleaner transportation, but treating their exhaust efficiently remains a significant challenge. Under stoichiometric conditions, three-way catalysts must simultaneously convert CH₄, CO, and NO_x while also withstanding high temperatures and moisture during long-term operation. CH₄ is particularly difficult to oxidize due to its high chemical stability, and NGV exhaust temperatures can exceed 800 °C, which accelerates catalyst deactivation. These factors make it difficult to achieve both high efficiency and long-term durability in NGV aftertreatment systems.

Recently, a research team led by researchers from the University of Nottingham Ningbo China and collaborating institutions developed a core-shell Pd@CeO₂/γ-Al₂O₃ three-way catalyst for stoichiometric NGV exhaust treatment. Their findings were published in the Chinese Journal of Catalysis (10.1016/S1872-2067(25)64926-6). In this design, a Pd core is encapsulated within a CeO₂ shell on a γ-Al₂O₃ support, forming a stable core-shell structure after high-temperature treatment. The study shows that this structure helps suppress Pd aggregation and creates active Pd-CeO₂ interfacial sites for exhaust treatment.

Among the prepared samples, the optimized Pd@Ce/Al (S-500) catalyst exhibited the best performance under stoichiometric NGV conditions. It achieved T₅₀ values of 336 °C for CH₄ conversion and 397 °C for NO conversion, and reduced the T₉₀ for CH₄ and NO by 113 and 177 °C, respectively, compared with the non-core-shell counterpart Pd-Ce/Al (S-500). Kinetic analysis further revealed a high CH₄ reaction rate of 3312.7 µmols^-1mol_Pd^-1 and a TOF of 0.032 s⁻¹ at 350 °C, along with a low E_a of 102.2 kJ/mol. These results indicate that the core-shell design improves low-temperature activity and facilitates the key reactions involved in exhaust treatment.

To understand the origin of this enhanced performance, the team combined spectroscopic characterization and DFT calculations. Their results revealed that the core-shell structure strengthens metal-support interactions, increases oxygen vacancies, and optimizes the Pd-CeO₂ interface as a primary active site. The calculations further showed that the energy barrier for the first C-H bond cleavage in methane activation decreases from 0.64 eV on PdO(101) to 0.18 eV on PdCeO(111), while barriers for NO-related reactions are also reduced. The catalyst also demonstrated exceptional durability. After hydrothermal aging at 800 °C for 16 hours, the aged Pd@Ce/Al (S-500) retained stable performance over a 100-hour test, with only slight losses of 5.5% in CH₄ conversion and 6.6% in NO conversion. These findings provide a promising strategy for cleaner and more durable NGV emission control.

About the journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top six journals in Applied Chemistry with a current SCI impact factor of 17.7.

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