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<p>Transition metal oxides, such as cobalt, manganese, and chromium oxide, exhibit remarkable potential as electrode materials for supercapacitor applications due to their versatile redox chemistry and high theoretical capacitance. This study investigates the structural and electrical properties of transition metal oxides (TMO), MnO<sub>2</sub>, Co<sub>3</sub>O<sub>4</sub>, and Cr<sub>2</sub>O<sub>3</sub>, along with their composites, with carbon nanotubes (CNTs) providing a foundational understanding of their suitability for energy storage. Pure metal oxides MnO₂, Co₃O₄, and Cr₂O₃ and their corresponding metal oxide–CNT composites were synthesized using the WOWS sol–gel method. XRD analysis confirmed the successful synthesis of pure oxides and composites with well-defined structural properties. The incorporation of CNTs into MnO₂ significantly enhanced the material's dielectric constant, AC conductivity, and dielectric loss in contrast to pure MnO<sub>2</sub>. This improvement can be attributed to the interaction between the CNTs and the metal oxide matrix, which facilitates charge transport and polarization mechanisms. CNTs lower grain-boundary resistance (Rgb), particularly in MnO₂/CNT (Z′&#xa0;~&#xa0;10<sup>2</sup> Ω at 3 MHz), validated by Nyquist plots and equivalent circuit models, emphasizing the CNTs' role in bridging resistive grain boundaries. The overall results show that MnO₂/CNT is suited for high-energy density storage, Co₃O₄/CNT excels in high-power devices (40% Rgb reduction), and Cr₂O₃/CNT is ideal for low-loss, high-frequency circuits, guided by Maxwell–Wagner and Koop’s polarization models. Electrochemical testing (cyclic voltammetry and galvanostatic charge–discharge) further validated the improvements: MnO₂/CNT displayed nearly double the capacitance of pristine MnO₂ (17.6 vs. 8.5 F g⁻<sup>1</sup> at 0.0125 A g⁻<sup>1</sup>), Co₃O₄/CNT showed superior rate capability, and Cr₂O₃/CNT offered stable low-loss behavior at high frequencies. These findings demonstrate that even minimal CNT incorporation (0.1 wt%) significantly enhances charge storage and transport, highlighting the complementary role of dielectric and electrochemical analysis in guiding the design of next-generation TMO-based supercapacitor electrodes</p>

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Composite of Metal Oxide with Carbon Nanotubes for Supercapacitor Applications

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Ruqia Masroor,
  • Haider Ali,
  • M. Anis-ur-Rehman

摘要

Transition metal oxides, such as cobalt, manganese, and chromium oxide, exhibit remarkable potential as electrode materials for supercapacitor applications due to their versatile redox chemistry and high theoretical capacitance. This study investigates the structural and electrical properties of transition metal oxides (TMO), MnO2, Co3O4, and Cr2O3, along with their composites, with carbon nanotubes (CNTs) providing a foundational understanding of their suitability for energy storage. Pure metal oxides MnO₂, Co₃O₄, and Cr₂O₃ and their corresponding metal oxide–CNT composites were synthesized using the WOWS sol–gel method. XRD analysis confirmed the successful synthesis of pure oxides and composites with well-defined structural properties. The incorporation of CNTs into MnO₂ significantly enhanced the material's dielectric constant, AC conductivity, and dielectric loss in contrast to pure MnO2. This improvement can be attributed to the interaction between the CNTs and the metal oxide matrix, which facilitates charge transport and polarization mechanisms. CNTs lower grain-boundary resistance (Rgb), particularly in MnO₂/CNT (Z′ ~ 102 Ω at 3 MHz), validated by Nyquist plots and equivalent circuit models, emphasizing the CNTs' role in bridging resistive grain boundaries. The overall results show that MnO₂/CNT is suited for high-energy density storage, Co₃O₄/CNT excels in high-power devices (40% Rgb reduction), and Cr₂O₃/CNT is ideal for low-loss, high-frequency circuits, guided by Maxwell–Wagner and Koop’s polarization models. Electrochemical testing (cyclic voltammetry and galvanostatic charge–discharge) further validated the improvements: MnO₂/CNT displayed nearly double the capacitance of pristine MnO₂ (17.6 vs. 8.5 F g⁻1 at 0.0125 A g⁻1), Co₃O₄/CNT showed superior rate capability, and Cr₂O₃/CNT offered stable low-loss behavior at high frequencies. These findings demonstrate that even minimal CNT incorporation (0.1 wt%) significantly enhances charge storage and transport, highlighting the complementary role of dielectric and electrochemical analysis in guiding the design of next-generation TMO-based supercapacitor electrodes