Phytoremediated nickel-enriched biochar composite for high-performance supercapacitors

Renewable and sustainable high-performance energy storage devices are essential to meet the needs of next-generation power sources. This study explores the use of the hyperaccumulator Dracaena trifasciata (snake plant) grown in manipulated soil (with Nickel) to explore a cost-effective, sustainable phytoremediation technique for synthesizing high-performance biocarbon electrode material. The synthesized Nickel-Biochar (Ni-Biochar) is treated with acid to enhance its processability and is then combined with an optimal amount of Polyaniline (PANI) to improve charge conductivity. The Ni-Biochar/PANI electrode demonstrates excellent electrochemical performance, with a specific capacitance of 638 F g −1 at 0.5 A g −1 in a three-electrode cell and notable stability, retaining 92 % of its capacity after 10,000 cycles. Additionally, the asymmetric supercapacitor made with Ni-Biochar/PANI achieves a specific capacitance of 163 F g −1 in a 3 M KOH solution. The Ragone plot for this device reveals an energy density of 57 Whkg −1 and a power density of 1259 W kg −1 . The device also shows outstanding long-term cyclic stability, retaining 90 % of its capacity after 5000 charge-discharge cycles. This high level of performance underscores the potential of utilizing plants as green carbon sources, which can be combined with various metal oxides and conducting polymers to produce hybrid nanomaterials , making them highly promising for sustainable supercapacitor electrode applications. • A sustainable biocarbon electrode was developed using Dracaena trifasciata via phytoremediation of Ni²⁺-contaminated soil. • Ni-Biochar/PANI electrode achieved 638 Fg⁻¹ at 1 A g⁻¹ with 92% retention over 10,000 cycles in a three-electrode system. • The asymmetric device delivered 164 Fg⁻¹ and maintained excellent performance in 3 M KOH electrolyte. • High energy and power densities (57 Wh/kg and 1259 W/kg) were achieved, indicating strong application potential. • The study offers a green route for hybrid nanomaterials combining biochar and metal hydroxides for supercapacitor electrode materials.