Cation distribution and defect engineering in spinel oxides MCo2O4 (M = Zn and Cu) toward efficient electrocatalytic interfaces for carbendazim sensing

Tunable cation distribution in spinel MCo2O4 enhances surface redox activity. • Microwave-assisted hydrothermal yields ZCO nanosheets and CCO nanorods with defects. • Oxygen vacancies and mixed cations boost interfacial charge transfer kinetics. • CCO/SPE shows high sensitivity and low LOD for Carbendazim detection. • Strong Carbendazim adsorption on spinel surfaces confirmed by experiment and theory. Spinel cobaltites MCo 2 O 4 (M is a divalent metal ion) nanomaterials have emerged as promising electrocatalysts for electrochemical sensing owing to their tunable cation distribution and redox-active metal centers. In this work, ZnCo 2 O 4 (ZCO) nanosheets and CuCo 2 O 4 (CCO) nanorods were prepared using a simple microwave-assisted hydrothermal method and subsequently employed to modify screen-printed electrodes (SPEs) for carbendazim (CBZ) detection. Structural analysis revealed distinct cation arrangements within the spinel lattice, particularly CCO exhibited mixed Cu/Co occupancy and abundant oxygen vacancies. Both modified electrodes significantly enhanced the electrochemical oxidation of CBZ compared with bare SPE, primarily due to the catalytic activity of the Co 3+ /Co 2+ redox couple. Notably, the CCO/SPE demonstrated superior sensing performance, arising from the synergistic effects of Cu 2+ /Cu + redox activity, high defect density, and one-dimensional morphology that promoted charge transfer and mass diffusion. The CCO/SPE sensor delivered promising analytical performance, featuring two linear ranges (0.1–10 and 10–500 µM), a detection limit of 0.07 µM, and a sensitivity of 5.97 µA µM −1 cm −2 . Combined experimental and theoretical analyses suggest strong CBZ adsorption on the MCo 2 O 4 spinel surface, highlighting spinel oxides as efficient electrocatalysts for CBZ pesticide sensing. Download: Download high-res image (241KB) Download: Download full-size image