Interfacial Engineering of MnCo2O4 Spinel Nanostructures Anchored on MWCN for Enhanced Pseudocapacitive Charge Storage in High-Performance Supercapacitors

<title>Abstract</title> <p> The development of high-performance Supercapacitor systems requires advanced electrode materials with high specific capacitance, superior rate capability, and long-term cycling stability. In this study, Manganese cobalt oxide and MnCo ₂ O ₄ @Multi-walled carbon nanotubes nanocomposites were successfully synthesized via a hydrothermal-assisted method followed by calcination at 400°C. Structural characterization confirmed the formation of a well-crystalline spinel MnCo ₂ O ₄ phase, while FESEM analysis revealed a porous hierarchical morphology with uniform distribution of nanoparticles on the conductive nanotube network. XPS confirmed mixed oxidation states Mn ²⁺ /Mn ⁴⁺ , Co ²⁺ /Co ³⁺ and oxygen-vacancy-rich surfaces, which enhanced redox activity and charge-transfer kinetics. Electrochemical studies using Cyclic voltammetry, Galvanostatic charge–discharge, and impedance analysis showed that the MnCo ₂ O ₄ @MWCNT electrode delivered a high specific capacitance of 1391 F g⁻¹ at 10 mV s⁻¹ and retained ~ 700 F g⁻¹ at higher scan rates, indicating excellent rate performance. The composite exhibited an energy density of ~ 48.5 Wh kg⁻¹ and a power density of ~ 2500–9000 W kg⁻¹ depending on current density, along with ~ 90% capacitance retention after 50,000 cycles and nearly 100% coulombic efficiency, confirming outstanding durability. Dunn’s method revealed a dominant pseudocapacitive behavior with a b-value of ~ 0.79, indicating a mixed diffusion-controlled and surface-controlled charge-storage mechanism. The enhanced electrochemical performance is attributed to the synergistic interaction between redox-active MnCo ₂ O ₄ nanoparticles and highly conductive MWCNT networks, which improves electron transport, electrolyte accessibility, and interfacial charge-transfer kinetics. Overall, the MnCo ₂ O ₄ @MWCNT nanocomposite demonstrates excellent electrochemical properties and is a promising electrode material for next-generation supercapacitors in portable electronics, electric vehicles, wearable devices, and renewable-energy storage applications. </p>