Facile Synthesis of Porous Carbonized Humic Acid as a Binder-Free Electrode for High-Capacitance Applications

Creating sustainable electrode materials that are high-performance and low-cost is essential for the progress of next-generation supercapacitors. This work reports a binder-free supercapacitor electrode material synthesized via in situ growth of coal-derived humic acid (HA) on nickel foam (Ni-foam). The material (CHA@Ni-foam) was fabricated using a simple hydrothermal method followed by calcination, resulting in a porous and conductive carbon nanonetwork with enhanced electrochemical properties suitable for fast charge storage. Thorough structural and compositional evaluations, involving scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), verified the effective carbonization and incorporation of HA onto Ni-foam. Electrochemical testing in both 3-electrode and symmetric 2-electrode configurations demonstrated high performance. This binder-free CHA@Ni-foam electrode exhibited an ultrahigh specific capacitance (Cs) of 905.3 F/g (at 1.15 A/g current density) in 2 M KOH electrolyte. The symmetric device delivered a high specific energy (E) of 75.0 W·h/kg and a specific power (P) of 150.2 W/kg within a 1.6 V operating window, with capacitance retention of 101.4% after 10,000 cycles of GCD. The combined benefits of low-cost coal-derived HA, binder-free architecture, and scalable fabrication suggest strong potential for CHA@Ni-foam as a high-performance electrode material for high-power energy storage applications.