La 2– x Sr x Ce 2– y Ni y O 7 Catalysts with Interstitial Nickel for Enhanced Dry Reforming of Methane

This study explores the catalytic performance of solution combustion-synthesized doped defective fluorite catalysts, La_2-xSr_xCe_2-yNi_yO₇, for the dry reforming of methane. A comprehensive structural analysis, supported by theoretical calculations, revealed that the adopted synthetic methodology enabled Ni doping beyond a critical concentration, leading to its occupation of the interstitial lattice sites. The optimally doped Ni-containing defective fluorite oxide La_1.9Sr_0.1Ce_1.7Ni_0.3O₇ exhibited superior catalytic activity with more than 70% conversion of CO₂ and CH₄ with an H₂/CO ratio of 0.7 for a 50-h reaction at 700 °C. The prolonged reforming reaction also resulted in minimal coke deposition (11 μg_c g_cat^-1 h^-1), primarily due to the oxidative dissociation pathway of methane, as revealed through mechanistic analysis. Detailed surface studies highlighted the crucial role of metal-support interactions, wherein facile electron transfer from Ni to Ce during the reaction contributed significantly to the enhanced catalytic performance. Thus, this study establishes a strategic framework for designing and developing defect-engineered oxide catalysts, paving the way for advanced materials in dry methane reforming.