(2ga) Tuning of Defects and Disorder in Lanthanum-Doped Ceria Nanoparticles: The Effect on Direct Methane Conversion to C2 Products

Research Interests: Catalyst Design, Structure/activity relationships, Natural Gas Conversion

The instability of petroleum prices and the advancements in extraction technologies of natural gas has increased the interest in the direct conversion of methane to C₂ products via oxidative coupling of methane (OCM) reactions. The design of catalysts by tailoring the structural defects and disorder has a significant impact on their performance. Within this context, in this work, the fine-tuning of oxygen defects in rod-like NPs was performed via La³⁺ doping (La_xCe_1-xO_2-1/2), x, in the 10-70 mol% range. The NPs characterization was performed by SEM, HRTEM, BERT, XRD, XPS and Raman spectroscopy, and the OCM catalytic performance was evaluated at 750 °C. The relative concentration of reagents (CH₄ and O₂) and products H₂, CO, CO₂, C₂H₄, and C₂H₆ was measured by an online mass spectrometer. XRD and Raman analysis revealed that the CeO₂ fluorite crystalline structure is essentially maintained in the doped nanorods, even for x = 0.7. The Raman spectra analysis indicates that La doping result in the formation of extrinsic and intrinsic oxygen defects that increase with increasing La concentration. The catalysts showed good performance for OCM with methane conversion up to 32% and C₂ selectivity up to 44% for x=0.5. In addition, all catalysts showed high stability within 20h time on stream. The demonstrated structural defect control on La-doped CeO₂ NPs provide important insights to improve the performance of OCM reaction.