Tuning of the D‐Orbital Electronic Configuration in Cobalt Octahedra for Efficient Electrochemical Sensing

Abstract Transition metal oxides have been extensively utilized in the development of electrochemical sensors, and exploring the relationship between their electronic structure and performance is crucial to improving sensing performance. In this study, A series of ZnCo 2 O 4 spinel oxides with varying volume ratios of high‐spin Co 3+ are synthesized to systematically control the d‐orbital electronic configuration and evaluate their electrochemical sensing performance for heavy metal ions. Combining the experimental and theoretical results, a positive correlation is demonstrated between electrochemical sensing performance and the volume ratio of high‐spin Co 3+ sites. By increasing the proportion of high‐spin Co 3+ sites, ZnCo 2 O 4 exhibits exceptional electrochemical sensing performance for Pb 2+ ions, achieving a sensitivity of 1.05 mA cm ECSA −2 µ m −1 and a detection limit of 0.456 n m , which is ≈2‐fold higher than that of the low‐spin state‐dominated oxide. Density functional theory calculations reveal that an increased spin state reduces electrons occupancy in the d xz and d yz orbitals of Co 3+ sites. Since these orbitals directly interact with adsorbed heavy metal ions, the reduction in electron occupancy weakens adsorption interactions, thereby enhancing the sensing performance. This work provides new insights into improving electrochemical sensing performance through the manipulation of spin states and orbital interactions.