Metal-organic framework-derived one-dimensional Pd@CeO2 catalysts with enhanced activity for methane oxidation

The interfacial structure in heterogeneous catalysis is important for effective and sequential methane oxidation due to its unique electronic structure. Here, we propose a facile strategy to fabricate a unique 1D Pd@CeO2-BDC catalyst from a corresponding Pd@Ce bimetallic metal organic frameworks (MOFs) nanostructure through thermal progress. By combining analysis of XRD, Raman, TEM, HRTEM and XPS results, the 1D mesoporous Pd@CeO2-BDC catalysts were rich in oxygen vacancies, and the Pd species were uniformly distributed on CeO2 (110) surface in the form of small PdO clusters and PdxCe1-xO2- s species. By reason of intense metal support interaction in the MOF skeleton, partial Pd atoms supersede Ce4+ in CeO2 lattice, which can significantly impact the catalyst's structure and electronic properties. H2-TPR and O2-TPD revealed that the aliovalent-substituted of Pd and Ce can greatly expedite the formation of active oxygen species and improve the redox properties, therefore stimulating an extraordinary catalytic properties for methane combustion. At a high space velocity of 60,000 mLg-1h 1, the 1 % Pd@CeO2-BDC catalyst achieved excellent catalytic performance with 90 % methane purification at 342.C. More importantly, in situ DRIFTS and density functional theory (DFT) calculations were conducted to establish the structure-activity relationship and reveal the reaction mechanism, proving that the excellent reactivity of MOF-derived catalysts can be attributed to lower energy barriers for methane activation on the reconstructed surfaces than surface adsorbed PdO. The present development for MOF-derived catalysts provides a new horizon for the construction of lean methane combustion catalysts.

Automated summary

In this study, a unique 1D Pd@CeO2-BDC catalyst with rich oxygen vacancies and uniformly distributed PdO clusters and PdxCe1-xO2-s species on CeO2 surface was fabricated. The intense metal support interaction in the MOF skeleton resulted in the substitution of Ce4+ in CeO2 lattice by Pd atoms, thus significantly affecting the structure and electronic properties of the catalyst. The excellent reactivity of MOF-derived catalysts was attributed to lower energy barriers for methane activation on the reconstructed surfaces, as revealed by experimental and theoretical calculations. This research provides a new approach for the construction of lean methane combustion catalysts.