Oxygen vacancy-dependent low-temperature performance of Ni/CeO2 in CO2 methanation†

Abstract

The transformative power of CO₂ methanation can efficiently transform greenhouse gases into high-value products, aligning with the carbon neutrality goals. However, achieving this target at low temperature requires cumbersome efforts in designing catalysts that possess high reactivity and selectivity. Focusing on understanding the pivotal role of alkaline (such as Ca) sites in catalyzing these reactions at lower temperature could be a way of strategically creating oxygen vacancies with varying activity gradients. Designing CaCe-SG via a sol–gel method in the current study to integrate Ca into the CeO₂ lattice marked the highly active moderate-strength alkaline centers which resulted in the intrinsic activity soaring by an impressive 400% compared to the conventional Ni/CeO₂ catalysts. Supported by H₂-TPD, Raman, and XPS analyses, a crucial revelation was unveiled where Ca modification induced a surge in the dispersion of active Ni species on Ni/CaCe-SG catalysts, thereby enhancing the abundant surface oxygen vacancies. In situ infrared spectroscopy further confirmed that the modified catalyst diligently followed the reaction pathway of CO₃H* → HCOO* → CH₄, culminating in the CO₂ methanation activity with a low-temperature catalyst via the meticulous optimization of synthesis methods that propelled the process forward to the anticipated oxygen vacancy-induced moderate-strength alkaline centers.