Mg-induced nanostructural evolution of Co3O4 toward enhanced supercapacitor applications

초록

Magnesium (Mg)-substituted cobalt oxide (Co3O4) thin films were synthesized using a simple and low-temperature chemical bath deposition method to investigate the role of Mg incorporation in tailoring their structural, morphological, and electrochemical properties. Increasing the Mg content from 10 to 80 at% induces a systematic evolution in surface morphology from nanorods to nanoflakes, interconnected nanofibers, nanocactus-like structures, nanowires, and nanobelts, while maintaining the cubic spinel Co3O4 structure. The resulting changes in surface architecture and defect chemistry strongly influence the charge-storage behavior, with the 20 at% Mg-substituted Co3O4 electrode, featuring an interconnected nanofiber network, exhibiting the best performance. The optimized electrode delivers a specific capacitance of 1230 F g−1 at 1 A g−1 and retains 89.5% of its initial capacitance after 5000 charge–discharge cycles. Furthermore, an asymmetric supercapacitor assembled using the optimized electrode and activated carbon achieves a specific capacitance of 170 F g−1 at 2 A g−1, a specific energy of 60.4 Wh kg−1 at a specific power of 1.6 kW kg−1, and 97.9% capacitance retention after 5000 cycles, with a coulombic efficiency of 94.3%. The enhanced performance is attributed to the synergistic effects of Mg-induced lattice modification, defect generation, improved charge-transfer characteristics, and the open interconnected nanofiber architecture, which provides abundant electroactive sites and facilitates efficient electrolyte-ion transport. These findings demonstrate that controlled Mg substitution is an effective strategy for engineering Co3O4 thin-film electrodes and developing high-performance asymmetric supercapacitors. © 2026 Published by Elsevier Ltd.

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