Capacitive Performance of Reduced Graphene Oxide Modified Sodium Ion-Intercalated Manganese Oxide Composite Electrode

The reduced graphene oxide modified sodium ion-intercalated manganese oxide (RGO-Na_xMnO₂) is designed as a supercapacitor electrode material. The layered intercalation compound Na_xMnO₂ is prepared through a solid-state reaction process. RGO-Na_xMnO₂ is then formed by the chemical reduction of graphene oxide coated Na_xMnO₂ through a hydrothermal process. RGO-Na_xMnO₂ is supported on the substrate of nickel form (NF) and titanium nitride (TiN) to form RGO-Na_xMnO₂/NF and RGO-Na_xMnO₂/TiN composite electrodes. Na_xMnO₂ has a particle aggregate structure with the individual particle size of 1–2 µm. RGO-Na_xMnO₂ composite shows the densely packed arrangement of particles with the particle aggregate size of 8 µm. RGO modification can well improve the electrical conductivity of RGO-Na_xMnO₂. The current response is highly enhanced from 0.127 A g⁻¹ for Na_xMnO₂/NF to 0.372 A g⁻¹ for RGO-Na_xMnO₂/NF at 2 mV s⁻¹. Furthermore, the TiN substrate with superior electrical conductivity and electrochemical anti-corrosion contributes to improving the electrochemical capacitance and cycle stability of RGO-Na_xMnO₂. RGO-Na_xMnO₂/TiN reveals higher specific capacitance (244.2 F g⁻¹ at 2.0 A g⁻¹) and higher cycling capacitance retention (99.7%) after 500 cycles at 2.0 A g⁻¹ than RGO-Na_xMnO₂/NF (177.1 F g⁻¹, 43.6%). So, RGO-Na_xMnO₂/TiN exhibits much higher capacitive performance than RGO-Na_xMnO₂/NF, which presents a potential application for electrochemical energy storage.