Biomass-derived carbon-supported Nickel hexacyanoferrate/carbon composites as advanced electrode materials for high-performance supercapacitors

In the modern world, supercapacitor electrode materials are crucial for developing energy storage systems that offer fast charging, high power density, and long-term stability to meet the growing demands of advanced electronics and renewable energy applications. Biomass resources are valuable sources for producing porous carbon materials due to their abundance, renewability, and cost-effectiveness. In this study, we synthesized nanosized NiHCF and directly decorated it on 2D biocarbon (BC) using an ultrasonic-assisted hydrothermal method. The crystalline structure and morphology of the as-prepared material were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses, revealing that pure NiHCF closely matches the standard cubic NiHCF pattern, while the NiHCF/BC hybrid displays small aggregates with irregular morphology, closely interacting with the BC sheet surface. The capacitive performance of the NiHCF/BC materials was evaluated through cyclic voltammetry (CV), galvanostatic charge/discharge tests (GCD), and electrochemical impedance spectroscopy (EIS) using a two-electrode system in 1 M Na2SO4 electrolyte, within a potential range of 0.0-1.6 V. The NiHCF//AC asymmetric device demonstrated an impressive specific capacitance of 1422 F g-1 and an energy density of 50.5 Wh kg-1, with a stability of 86.3% after 5000 cycles. In contrast, the pristine NiHCF electrode exhibited a lower specific capacitance of 1000.2 F g-1 at 1 A g-1 and retained only 82.2% of its initial capacitance after 5000 cycles. The excellent electrochemical performance of the NiHCF/BC hybrid electrode material is attributed to the enhanced conductivity of the biocarbon and the good crystallinity of NiHCF. The outstanding performance of the NiHCF/BC hybrid electrode presents strong potential for the development of high-performance supercapacitor, making them ideal for portable and wearable energy storage devices.