Isomorphously substituted cerium induced oxygen vacancy and medium basicity in Ni/fibrous silica catalyst for superior low-temperature CO₂ methanation

A series of promoters (Ce, La, Mo, and Zr) was introduced into the Ni/CHE-SM catalyst by using the impregnation method and tested for CO₂ methanation. Among these, Ni-Ce/CHE-SM possessed a high CO₂ conversion of 80 % at 250 °C, signifying its potential at low temperature. The superior performance of Ni-Ce/CHE-SM was attributed to the formation of Si-O-Ni and Si-O-Ce species, as confirmed by FTIR-KBr analysis. XPS and CO₂-TPD analyses revealed an abundance of oxygen vacancies existed within Ni-Ce/CHE-SM, resulting in enhancement of basicity amount and strength. In addition, Raman analysis showed the existence of three and four silica member rings which was believed that the Si atom be substituted with the Ce atom, thus contributing to create more oxygen vacancies. Hence, additional active sites were provided which enhance the adsorption of reactant molecules and improve the production of CH₄, thus emphasizing the greater potential of Ni-Ce/CHE-SM in CO₂ methanation application.