Complexation-Driven Design of Ultrafine Manganese Ferrocyanide-Based Electrodes for High-Performance Supercapacitors Enabling Low-Frequency Waveform Generation

Supercapacitors are widely recognized as essential energy storage devices because of their fast-charging capability, high power output, and excellent cycle stability. These features make them highly suitable for various applications such as electric vehicles, backup power systems, and portable electronics. In this study, manganese ferrocyanide (MFC) nanoparticles were synthesized via an organic-molecule-assisted complexation method and investigated as electrode materials for advanced supercapacitors. Structural analysis confirmed a crystalline cubic structure with Mn2+ and Fe2+ ions arranged in octahedral coordination. The MFC-based electrode demonstrated pseudocapacitive behavior with a specific capacitance (SPC) of 584 F·g–1 at 5 A·g–1 in a half-cell configuration. An asymmetric supercapacitor (ASC) utilizing activated carbon as the negative electrode and MFC as the positive electrode achieved a maximum SPC of 77 F·g–1 at 1 A·g–1, with maximum energy density, EDn, of 54 Wh·kg–1 and power density, PDn, of 6.0 kW·kg–1. The device at 2 A·g–1 retained 87% of its initial SPC and maintained 90% Coulombic efficiency after 5000 continuous charge–discharge cycles, demonstrating the long-term durability of the device. The ASC was integrated into an oscillator circuit, demonstrating low-frequency waveform generation suitable for electronic circuit applications. The dual functionality highlights the potential of manganese ferrocyanide-based material for both energy storage and signal generation in low-power electronic systems.