Enhanced CO 2 Methanation Activity of Sm 0.25 Ce 0.75 O 2-δ -Ni by Modulating the Chelating Agents-to-Metal Cation Ratio and Tuning Metal-Support Interactions.

Highly active and selective CO 2 methanation catalysts are critical to CO 2 upgrading, synthetic natural gas production, and CO 2 emission reduction. Wet impregnation is widely used to synthesize oxide-supported metallic nanoparticles as the catalyst for CO 2 methanation. However, as the reagents cannot be homogeneously mixed at an atomic level, it is challenging to modulate the microstructure, crystal structure, chemical composition, and electronic structure of catalysts via wet impregnation. Herein, a scalable and straightforward catalyst fabrication approach has been designed and validated to produce Sm 0.25 Ce 0.75 O 2-δ -supported Ni (SDC-Ni) as the CO 2 methanation catalyst. By varying the chelating agents-to-total metal cations ratio ( C / I ratio) during the catalyst synthesis, we can readily and simultaneously modulate the microstructure, metallic surface area, crystal structure, chemical composition, and electronic structure of SDC-Ni, consequently fine-tuning the oxide-support interactions and CO 2 methanation activity. The optimal C / I ratio (0.1) leads to an SDC-Ni catalyst that facilitates C-O bond cleavage and significantly improves CO 2 conversion at 250 °C. A CO 2 -to-CH 4 yield of >73% has been achieved at 250 °C. Furthermore, a stable operation of >1500 hours has been demonstrated, and no degradation is observed. Extensive characterizations were performed to fundamentally understand how to tune and enhance CO 2 methanation activity of SDC-Ni by modulating the C / I ratio. The correlation of physical, chemical, and catalytic properties of SDC-Ni with the C / I ratio is established and thoroughly elaborated in this work. This study could be applied to tune the oxide-support interactions of various catalysts for enhancing the catalytic activity.