Ceria engineering in nickel catalysts to improve CH4 selectivity and yield for CO methanation

Abstract

CO methanation on nickel-based catalysts is often plagued by low selectivity and stability due to aggregation and sintering of nickel and carbon deposition on the catalyst surface. In this work, we develop a 10 %CeO2-20 %NiO/p-SiO2 nanosphere catalyst with porous structure that presents an improved CH4 selectivity and yield in contrast with the reported catalysts. Moreover, experimental data coupled with density functional theory calculations reveal that oxygen vacancies in under-stoichiometric CeO2-x are maximized through the reductive pretreatment before the reaction, acting as the mobile reactive sites and participating CO methanation. That is, oxygen vacancies assist to adsorb CO molecules, weaken the CO binding strength, further break CO bond to improve CH4 formation. Afterward, oxygen is filled into the oxygen vacancy, and carbon is hydrogenated to generate CH4 molecules. These findings may shed light on the role of ceria as a promoter, especially for heterogeneous catalytic reactions.