Facilitating CO2 methanation over oxygen vacancy-rich Ni/CeO2: Insights into the synergistic effect between oxygen vacancy and metal-support interaction

Abstract

The catalytic hydrogenation of CO2 into CH4 is a versatile strategy to realize green development goals, whereas developing low-cost and high-performance catalysts remains a significant challenge. Herein, highly active Ni0/NiO supported on oxygen vacancy-rich CeO2 (Ni/CeO2-Ov-R) was designed, which exhibited ∼76 % CO2 conversion coupled with 100 % CH4 selectivity at a low temperature of 250 °C. In addition, such satisfactory reaction performance could be maintained over 80 h at 300 °C. The density functional theory (DFT) calculations elaborated that oxygen vacancies were more easily formed on the CeO2 (1 1 0) plane of Ni/CeO2-Ov-R. Compared with Ni/CeO2-Ov-medium (Ni/CeO2-Ov-M) and Ni/CeO2-Ov-poor (Ni/CeO2-Ov-P) with relatively insufficient oxygen vacancy, the copious oxygen vacancies of Ni/CeO2-Ov-rich was apt to enhance the interaction between the CeO2 support and Ni species as confirmed through H2-TPR and XPS. Noteworthily, the abundant medium-strength basic sites and surface oxygen vacancy of Ni/CeO2-Ov-rich were more conducive to upshifting the activation adsorption of CO2 and accelerate the conversion of intermediates. Besides, the oxygen vacancies also make a great contribution to the enhancement of the potential for hydrogen dissociation because of the enhanced number of exposed Ni0. In situ DRIFTS displayed that the CO and formate (HCOO–) routes co-existed on Ni/CeO2 catalysts, revealing that oxygen vacancy and exposed Ni0 boosted the CO2 and H2 activation. This work proposes a deeper insight into the precise regulation of the oxygen vacancy of Ni/CeO2 catalyst and opens a path for exploiting CO2 methanation catalysts with a potential application.