Active-site evolution in dual-sublattice cobalt-based spinels for governing electrocatalytic oxidation pathways

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Cobalt (Co)-based spinel oxides have emerged as versatile electrocatalysts for a wide range of oxidation reactions. However, their catalytic behavior remains difficult to rationalize due to the dynamic coupling between bulk structure and surface reconstruction under operating conditions. Despite their tunable cation distribution, spin states, and defect chemistry, a unified understanding of how these intrinsic features govern reactivity across different oxidation pathways is still lacking. This review establishes an active-site-evolution framework for Co-based spinels. The roles of geometric and electronic characteristics as well as their dynamic reconstruction in determining catalytic function, are systematically analyzed. Then, reaction mechanisms and catalyst design principles are discussed across representative oxidation pathways, including oxygen evolution, selective organic oxidation for value-added chemical production, low-potential anodic oxidation for energy-saving electrolysis, and electrochemical deep oxidation for environmental remediation. External-field-assisted strategies are further highlighted, where magnetic and optical fields introduce additional degrees of freedom for modulating active-site states and oxidation-pathway selection. By linking intrinsic structural features with dynamic surface evolution, this review moves beyond descriptive correlations toward a mechanism-informed understanding of Co-based spinel electrocatalysts, guiding the rational design of catalysts for sustainable electrochemical oxidation.