Synergistic tuning of Ni(111) facets and oxygen vacancy on citric acid-modified Ni/CeO2 for enhanced CO2 methanation

초록

The development of efficient and durable catalysts for CO2 methanation is essential for sustainable energy conversion and carbon utilization. Herein, a citric acid-assisted synthesis strategy is employed to tune facetinduced metal-support interactions (MSI) in Ni/CeO2 catalysts (NC-x: x = Ni:CeO2 molar ratio). By regulating precursor complexation and interfacial assembly during the sol-gel synthesis, citric acid effectively promotes intimate Ni-CeO2 interfacial contact, suppresses Ni aggregation, and generates a defect-rich nanostructure with enhanced Ni(111) exposure and oxygen-vacancy density. The optimized NC-10 catalyst markedly improves methanation performance, achieving 83.8% conversion of 10 vol% CO2 into CH4 (99.9% selectivity) at 350 degrees C and a high weight hourly space velocity of 60,000 mL g- 1 h- 1. This performance is 5-fold higher than that of the untreated benchmark catalysts and remains stable over 100 h of continuous operation. Temperature-dependent in situ diffuse reflectance infrared Fourier transform spectra reveal that ceria-derived basic/defect sites promote CO2 adsorption and activation, whereas highly dispersed Ni(111) facets facilitate H2 dissociation and supply reactive H atoms for the sequential hydrogenation of formate/carbonate surface species to CH4. These results demonstrate that the cooperative effects of enhanced Ni dispersion, favorable Ni(111) exposure, defect-rich ceria, and strong Ni-CeO2 interfacial coupling, induced by the citric acid-assisted synthesis strategy, are centeral to improving catalytic CO2 methanation activity, stability, and low-temperature reaction kinetics.

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