Synergistic Ti₃C₂Tₓ MXene@Co₃O₄ Nanocomposite for Efficient Energy Storage Devices

The Ti₃C₂Tₓ MXene was obtained from the parent Ti₃AlC₂ MAX phase through selective HF etching, followed by integration with cobalt oxide to produce a hybrid electrode designed for supercapacitor applications. X-ray diffraction confirmed the removal of Al layers,  enlarged interlayer spacing and exfoliation. Well-defined cubic spinel structure, and crystallite size showed a reduction from ~40.77 nm in pristine MAX to ~10.68 nm in etched MXene and ~24.33 nm in cobalt oxide, a trend favourable for enhanced electrochemical activity. FTIR spectra revealed abundant surface groups (–OH, –O, –F) on MXene and characteristic Co–O vibrations at tetrahedral and octahedral sites, confirming phase purity and strong interfacial bonding. UV–visible analysis displayed broad metallic absorption for MXene, consistent with high carrier density, while cobalt oxide showed typical semiconducting behaviour, highlighting their complementary electronic properties. FESEM micrographs shows observable modifications from layered structure of well-aligned stacks with the accordion-like shape to rough, porous surface with many spaces and cavities which finally converts in to heterogeneous microstructure with evenly distributed cobalt oxide nanoparticles throughout the stacked MXene sheets. TEM and EDAX further demonstrated the transformation of dense MAX particles into exfoliated MXene nanosheets with complete Al removal, alongside uniform rod-like cobalt oxide nanoparticles of high elemental purity. Electrochemical testing revealed that the Ti₃C₂Tₓ MXene@cobalt oxide composite achieved a specific capacitance of 871.04 F/g at 75 mV/s, with an energy density of 6.67 Wh/kg at a power density of 34 kW/kg. EIS analysis, fitted with a Voigt-type equivalent circuit (χ² ≈ 1.24 × 10⁻²), showed low solution resistance (Rₛ ≈ 1.09 Ω), reduced charge transfer resistance, and efficient ion transport without a pronounced Warburg contribution. The superior performance arises from the synergy between the electric double-layer capacitance of MXene and the pseudocapacitive redox activity of cobalt oxide, underscoring the potential of this hybrid electrode for next-generation supercapacitors.