One‐Step Controllable Synthesis of Mesoporous MgCo₂O₄ Nanosheet Arrays with Ethanol on Nickel Foam as an Advanced Electrode Material for High‐Performance Supercapacitors

In recent years, ternary transition metal oxides (TTMOs), especially spinel type TTMOs have attracted widespread attention as promising candidates for electrode materials. Among all of the popular TTMOs, MgCo₂ O₄ is an outstanding one, owing to its superior theoretical capacitance. In this work, MgCo₂ O₄ nanosheet arrays (NSAs) grown directly on nickel foams were fabricated through a facile hydrothermal process at 120 °C for 4 h. With a series of structural and morphological characterization techniques, it was found that the ethanol played a key role in controlling the composition and morphology during the synthesis process. The MgCo₂ O₄ NSAs exhibited a superior specific capacitance of 853.06 C g^-1 (at 1 mA cm^-2 ) and enhanced cycling performance, with 94.65 % of initial capacitance retained after 3000 cycles when used as a binder-free integrated electrode for electrochemical supercapacitors; much higher than other reported data for MgCo₂ O₄ as well. The excellent electrochemical properties mainly came from the unique morphology of the MgCo₂ O₄ NSAs. This study will demonstrate the applications of MgCo₂ O₄ NSAs based large-scale supercapacitors grown on low-cost nickel foams.