Carbon framework controlled charge storage and ion-transport dynamics in hydrothermally synthesized MnS nanocomposite...

Contemporary supercapacitors require electrode materials that combine high charge-storage capability with rapid and reversible ion/electron transport, rather than relying solely on specific capacity. In this work, manganese sulfide (MnS) and its carbon-based nanocomposites (MnS/rGO and MnS/CNT) were synthesized via a facile hydrothermal route to investigate how different carbon architectures regulate charge-storage behavior, ion transport, and electrochemical kinetics. Structural and surface analyses confirm the formation of MnS with partial surface oxidation and its uniform integration within reduced graphene oxide (rGO) sheets and carbon nanotube (CNT) networks. Among the investigated electrodes, MnS/rGO exhibits a markedly enhanced specific surface area (222 m² g^-1) and an open mesoporous architecture, providing abundant electroactive sites and efficient ion-diffusion pathways. Electrochemical measurements demonstrate that MnS/rGO delivers the most favorable pseudocapacitive response, achieving a specific capacity of 404.2 C g^-1 at 1.1 A g^-1 and retaining higher capacity than MnS and MnS/CNT at elevated current densities. To directly link this performance to transport properties, electrochemical impedance spectroscopy is used to extract ionic conductivity, relaxation time, exchange current density, and kinetic rate constant for all electrodes. MnS/rGO shows the highest ionic conductivity (16.3 S m^-1), the shortest relaxation time (0.077 s), and enhanced kinetic parameters (J ₀ ≈ 6.8 × 10^-3 A g^-1, k ≈ 2.4 × 10^-8 cm s^-1), evidencing faster ion migration and interfacial charge transfer than pristine MnS or MnS/CNT. Collectively, these results identify 2D rGO scaffolding as an effective strategy to co-optimize structure, transport, and pseudocapacitive kinetics in MnS-based electrodes, positioning MnS/rGO as a strong candidate for high-performance supercapacitors.