Optimizing the oxide support composition in Pr-doped CeO2 towards highly active and selective Ni-based CO2 methanation catalysts

In this study, Ni catalysts supported on Pr-doped CeO2 are studied for the CO2 methanation reaction and the effect of Pr doping on the physicochemical properties and the catalytic performance is thoroughly evaluated. It is shown, that Pr3+ ions can substitute Ce4+ ones in the support lattice, thereby introducing a high population of oxygen vacancies, which act as active sites for CO2 chemisorption. Pr doping can also act to reduce the crystallite size of metallic Ni, thus promoting the active metal dispersion. Catalytic performance evaluation evidences the promoting effect of low Pr loadings (5 at% and 10 at%) towards a higher catalytic activity and lower CO2 activation energy. On the other hand, higher Pr contents negate the positive effects on the catalytic activity by decreasing the oxygen vacancy population, thereby creating a volcano-type trend towards an optimum amount of aliovalent substitution.