Tailoring metal-support interactions via tuning CeO2 particle size for enhancing CO2 methanation activity over Ni/CeO2 catalysts

[Display omitted] •MSI and related oxygen vacancy concentration were modulated by CeO2 size.•More surface oxygen vacancies were created at the Ni-CeO2 interface.•The formate is identified the key intermediates for CO2 methanation.•The relationship between oxygen vacancies and methanation activity was explored. Interfaces derived from metal-support interaction (MSI) and related oxygen vacancies are generally recognized as main factors affecting on CO2 methanation performance, but the interaction between these two factors is not yet very clear. To better understand the role of complicated MSI and associated oxygen vacancy for CO2 methanation, we designed the CeO2 nanocubes with different sizes as support and prepared supported Ni catalysts to study the relationship between MSI and catalytic performance. HRTEM, XRD, BET, Raman and XPS characterization results confirmed that the MSI and related oxygen vacancy concentration could be modulated by CeO2 size. The impact of oxygen vacancy and phase interface on activating reactant molecules (CO2/H2) was evidenced by HRTEM and CO2/H2-TPD results. The CO2 conversion rate on the Ni/CeO2-6M at 548 K is about three times that on the Ni/CeO2-12M, which is attributed to its lower activation energy. Furthermore, in-situ FT-IR results for CO2 hydrogenation on the Ni/CeO2-6M proved that CO2 methanation followed the formate pathway and the methoxy/carbonyls are key intermediates to produce CH4. The structure-effect relationship was further explored to show the size effect on Ni-CeO2 interaction interfaces and enhanced methanation performance.