Deciphering the role of Ni particle size and nickel-ceria interfacial perimeter in the low-temperature CO2 methanation reaction over remarkably active Ni/CeO2 nanorods

The structure sensitivity of CO2 methanation was explored over nickel particles (10-25 nm) supported on CeO2 nanorods. An optimum Ni particle size of 20 nm was revealed, with the corresponding sample demonstrating remarkable activity, i.e., 187 mu mol CH4 g(-1) s(-1) and 92 % CH4 yield at 275 degrees C, which is among the highest ever reported. Notably, the intrinsic activity on the basis of the exposed Ni sites or Ni-ceria perimeter is largely in-dependent of the Ni size, showcasing that neither the exposed Ni sites nor the Ni-ceria interface can be employed as activity descriptors. A compromise between the length of the metal-support perimeter and the competitive presence of larger Ni particles is necessary for the optimum activity. On the grounds of a structure-sensitivity analysis, the superior activity of larger Ni particles could be attributed to the presence of under-coordinated step and kink sites, instead of largely inactive terrace sites.