Lattice capacity-dependent activity for CO 2 methanation: crafting Ni/CeO 2 catalysts with outstanding performance at low temperatures.

In the pursuit of understanding lattice capacity threshold effects of oxide solid solutions for their supported Ni catalysts, a series of Ca 2+ -doped CeO 2 solid solutions with 10 wt% Ni loading (named Ni/Ca x Ce 1- x O y ) was prepared using a sol-gel method and used for CO 2 methanation. The lattice capacity of Ca 2+ in the lattice of CeO 2 was firstly determined by the XRD extrapolation method, corresponding to a Ca/(Ca + Ce) molar ratio of 11%. When the amount of Ca 2+ in the Ca x Ce 1- x O y supports was close to the CeO 2 lattice capacity for Ca 2+ incorporation, the obtained Ni/Ca 0.1 Ce 0.9 O y catalyst possessed the optimal intrinsic activity for CO 2 methanation. XPS, Raman spectroscopy, EPR and CO 2 -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 x Ce 1- x O 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 CO 2 methanation reaction and enabling efficient catalyst screening.