Lattice capacity-dependent activity for CO2 methanation: crafting Ni/CeO2 catalysts with outstanding performance at low temperatures

Abstract

In the pursuit of understanding lattice capacity threshold effects of oxide solid solutions for their supported Ni catalysts, a series of Ca²⁺-doped CeO₂ solid solutions with 10 wt% Ni loading (named Ni/Ca_xCe_1−xO_y) was prepared using a sol–gel method and used for CO₂ methanation. The lattice capacity of Ca²⁺ in the lattice of CeO₂ was firstly determined by the XRD extrapolation method, corresponding to a Ca/(Ca + Ce) molar ratio of 11%. When the amount of Ca²⁺ in the Ca_xCe_1−xO_y supports was close to the CeO₂ lattice capacity for Ca²⁺ incorporation, the obtained Ni/Ca_0.1Ce_0.9O_y catalyst possessed the optimal intrinsic activity for CO₂ methanation. XPS, Raman spectroscopy, EPR and CO₂-TPD analyses revealed the largest amount of highly active moderate-strength alkaline centers generated by oxygen vacancies. The catalytic reaction mechanisms were revealed using in situ IR analysis. The results clearly demonstrated that the structure and reactivity of the Ni/Ca_xCe_1−xO_y catalyst exhibited the lattice capacity threshold effect. The findings offer a new venue for developing highly efficient oxide-supported Ni catalysts for low-temperature CO₂ methanation reaction and enabling efficient catalyst screening.