Local Oxygen Chemical Potential Determines Cobalt‐Ceria Interfacial Catalysis in CO ₂ Hydrogenation

Abstract Exploring the restructuring mechanism of solid catalysts is of pivotal importance for the rational design of efficient catalysts, yet remains a significant challenge. Traditional chemical potential theory assumes a spatially uniform gas reservoir with a well‐defined chemical potential but neglected the spatial variations induced by surface reactions, mass transportation, and temperature gradients in the operando conditions. Here, we employ a thermodynamics‐guided strategy, integrated with experimental models initiated from distinct precursor structures, to demonstrate the structure of restructured catalyst determined by the local oxygen chemical potential ( μ O ). Using cobalt‐ceria catalyzed CO 2 hydrogenation as a proof‐of‐concept system, comprehensive characterizations reveal that supported cobalt species undergo in situ restructuring during reaction processes, either reducing oxidative cobalt species to lower oxidation states or oxidizing metallic cobalt to positive valence states, ultimately forming CoO x ensembles with Co(II) as the primary component. Starting from either metallic Co or CoO x , the resulting differences in catalytic activity modify the local atmosphere and the μ O near catalyst surface. This leads to the formation of distinct CoO x ensembles, which in turn dictate the divergent catalytic performance. These findings provide a comprehensive physical picture elucidating the intrinsic correlation between the environmental atmosphere and corresponding structure of restructured catalysts.