Probe Sonication-Driven Synthesis of Nb2C MXene/NiCo2O4 Nanocomposites for High-Performance Symmetric Supercapacitors

Abstract

The persistent energy-power density trade-off in supercapacitors necessitates advanced electrode materials with synergistic ion transport and redox capabilities. Herein, we report a sonication-assisted synthesis of Nb2C/NiCo2O4 (NCN) nanocomposites, prepared via selective HF-etching of the Nb2AlC MAX phase followed by hybridization with 10–50 wt % NiCo2O4 nanoparticles. Unlike conventional hydrothermal and solvothermal methods that typically require high-temperature (120–200 °C) processing for several hours (6–12 h), the proposed sonication-assisted strategy enables composite formation at room temperature within 3 h, eliminates autoclave processing, reduces energy consumption, suppresses Nb2C restacking, and promotes homogeneous dispersion of NiCo2O4 nanoparticles. The sonication-driven approach enables rapid room-temperature compositing, preventing MXene restacking while ensuring uniform nanoparticle dispersion. XRD analysis shows the presence of Nb2C nanosheets having a 002 peak with NiCo2O4 nanoparticles having 311, 400, and 511 peaks. Raman spectroscopy reveals the preservation of characteristic E1g, D, and G modes of Nb2C MXene alongside F2g, Eg, and A1g vibrational modes of cubic spinel NiCo2O4. Structural and morphological analyses confirm the uniform integration of NiCo2O4 within the layered Nb2C framework. The composite electrode comprising Nb2C/NiCo2O4 (1:1 by weight, NCN-50), tested in a 3 M KOH electrolyte under a three-electrode configuration, exhibited a specific capacitance of 1312.08 F g–1 at 3 A g–1. Trasatti and Cottrell’s analysis eludicated the charge storage and transport mechanisms revealing mixed capacitive-diffusion-controlled behavior. A symmetric supercapacitor assembled using NCN-50 electrodes delivered an energy density of 9.81 Wh kg–1 at 350 W kg–1 and retained 96.1% capacitance after 5000 cycles demonstrating excellent cycling stability. This work establishes sonication-driven MXene-Transition Metal Oxide (TMO) hybridization as a scalable, energy efficient methodology for next-generation electrochemical energy storage providing conductive frameworks with accessible redox sites while avoiding high-temperature processing.