Insights into the contribution of oxygen vacancies on CO2 activation for dry reforming of methane over ceria-based solid solutions

Exploring the contribution of oxygen vacancies in ceria-based materials is critical for understanding the role they play in catalysis. In this study, a series of aliovalent (La3+, Nd3+, Sm3+, and Eu3+) metal ions ceria-based solid solutions were synthesized and comparatively characterized for their application in dry reforming of methane (DRM). The concentration and reactivity of oxygen vacancies either on the surface or in the bulk, which are identified as active sites for direct CO2 dissociation, were calculated through a combination of transient response experiments and numerical simulations. The results show that the substitution of Ce4+ with trivalent ions increases oxygen vacancies, which improves the activation of CO2 and facilitates the oxidation of the formed coke. The CO2 activation rate was identified as a descriptor for predicting the catalytic stability. This work demonstrates the composition-dependent interplay among ceria-based materials and provides a pathway to tailor the reactivity of ceria-based catalysts.