Phytoremediation of Nickel Via Water Hyacinth for Biocarbon-Derived Supercapacitor Applications

Water hyacinth (Eichhornia crassipes, WH) is cultivated in a hydroponic system containing various concentrations of Ni2+ to demonstrate phytoremediation techniques as a facile, low-cost, and sustainable method for synthesizing high-performance biocarbon electrode materials. A high specific capacitance of 541 F g(-1) in 2 m potassium hydroxide (KOH) is achieved for WH-5 biocarbon with an energy density of 30.5 Wh kg(-1). Materials are assembled into a coin cell supercapacitor capable of lasting 10 000 cycles with 100% capacitance retention. Surface area characterizations support these results with an S-BET of 3429 m(2) g(-1), a V-BET of 2.13 cm(3) g(-1), and an S-p avg of 2.5 nm, indicating enhanced pore formation and functional group cleaving. Raman spectroscopy, attenuated total reflectance Fourier transform IR (ATR-FTIR), and X-ray diffraction (XRD) give further insight into physical characteristics of the biocarbon that lead to improved electrochemical performance. This work describes an optimal concentration of preabsorbed Ni2+ catalyst (5 ppm in H2O) capable of achieving 98% of theoretical capacitance and value-added environmental cleanup associated with synergistic remedial techniques.