Local Oxygen Chemical Potential Determines Cobalt-Ceria Interfacial Catalysis in CO₂ Hydrogenation

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 CO₂ 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.