Synergistic Spin‐State Regulation and Curvature‐Driven Electric Field Enhancement of Nanobead Arrays for High‐Efficiency Chlorine Evolution Reaction

Abstract The development of non‐precious metal‐based chlorine evolution reaction (CER) catalysts with superior intrinsic activity, favorable kinetics, and high current efficiency remains a critical challenge. In this work, Br‐functionalized Co ₃ O ₄ nano‐bead arrays (Br‐Co ₃ O ₄ ‐NBAs) are constructed, exhibiting exceptional CER kinetics and selectivity through the synergistic interplay of spin‐state modulation and curvature‐driven structural engineering. The introduction of Br species and curvature defects weakens the crystal field splitting energy, inducing the formation of high spin state catalyst centers for facilitated electron transfer and intermediate adsorption. Furthermore, the high‐curvature architecture significantly enhances electrocatalytic performance through dual mechanisms: it drives interfacial local near‐field electric fields to achieve directional Cl ⁻ enrichment, while ducing bubble adhesion energy barriers to accelerate gas desorption. Therefore, the optimized Br‐Co ₃ O ₄ ‐NBAs achieve an unprecedented overpotential of 46 mV at 10 mA cm ⁻ ² while maintaining >98% CER selectivity across broad operational windows (pH 2–7, NaCl 0.5–5 M), outperforming commercial DSA catalysts. The reaction mechanism studies demonstrate that the cooperative interplay between high‐spin Co centers and curvature‐enhanced electric fields preferentially activates the Krishtalik pathway, shifting the rate‐determining step to the Volmer adsorption process. This work establishes multiscale integration of spin‐state modulation and nanocurvature engineering for designing chlorine evolution electrocatalysts with enhanced activity and selectivity.