Comparative study of Ni–CeO2 catalysts prepared by impregnation and coprecipitation for CO2 methanation

This study explores how synthesis methods affect the structure and CO2 methanation performance of Ni–CeO2 catalysts prepared by coprecipitation and impregnation under identical conditions. Coprecipitation generated particles below 100 nm with uniform elemental distribution, together with large bulk-like particles exhibiting locally concentrated Ni species, attributed to differences in hydroxide solubility. Impregnation, by contrast, produced very large particles (> 500 nm) with smaller particles attached, while maintaining relatively homogeneous elemental distribution. Coprecipitated catalysts showed slightly higher surface area and oxygen vacancy concentration, resulting in higher apparent turnover frequencies (TOFapp) below 300 °C due to enhanced CO2 adsorption and high Ni site density. However, at temperatures above 350 °C, impregnated catalysts displayed higher CH4 selectivity and TOFapp, indicating reduced kinetic limitations and more efficient active-site utilization. These results provide insights for rational design of efficient CO2 methanation catalysts.