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

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 Ni-0/NiO supported on oxygen vacancy-rich CeO2 (Ni/CeO2-Ov-R) was designed, which exhibited similar to 76 % CO2 conversion coupled with 100 % CH4 selectivity at a low temperature of 250 degrees C. In addition, such satisfactory reaction performance could be maintained over 80 h at 300 degrees 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 H-2-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 Ni-0. In situ DRIFTS displayed that the CO and formate (HCOO-) routes co-existed on Ni/CeO2 catalysts, revealing that oxygen vacancy and exposed Ni-0 boosted the CO2 and H-2 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.