Sustainable Ni/NiO-carbon aerogel composite derived from water hyacinth for high-performance supercapacitor electrodes

The pursuit of sustainable and high-performance electrode materials is crucial for advancing next-generation energy storage technologies. In this work, a Ni/NiO–carbon aerogel composite (Ni/NiO–CAC) was synthesized from water hyacinth (WH) an abundant and renewable biomass source, through a green and facile multi-step process involving NaOH pretreatment, aerogel formation, carbonization, and nickel incorporation, where the alkaline treatment improved cellulose purity and structural homogeneity. The integration of Ni/NiO nanoparticles within the carbon aerogel framework endowed the material with hierarchical porosity, enlarged surface area, and abundant redox-active sites. Among the prepared samples, the Ni/NiO–CA-10 composite (containing 10 wt% Ni loading) exhibited a remarkably high specific surface area of 1054 m 2 g⁻¹ and delivered a specific capacitance of 312.5 F g⁻¹ at 1 A g⁻¹ , while retaining 87 % of its capacitance after 1700 charge–discharge cycles at 10 A g⁻¹ , demonstrating outstanding rate capability and cycling durability. Electrochemical impedance spectroscopy (EIS) revealed reduced internal resistance and enhanced ion transport efficiency in the Ni/NiO composite compared to pristine carbon aerogels. This study provides a sustainable approach for converting invasive aquatic biomass into high-value electrode materials, highlighting the synergistic effects of the Ni/NiO-carbon interface in boosting supercapacitor performance. • Ni/NiO–CAC synthesized from water hyacinth via a sustainable green process. • Optimized Ni/NiO–CAC-10 delivered 312.5 F g⁻¹ at 1 A g⁻¹ with high efficiency. • Capacitance retention of 87 % achieved after 1700 charge–discharge cycles. • BET analysis revealed 1054 m 2 g⁻¹ surface area and a hierarchical pore network. • Demonstrates biomass valorization into high-performance supercapacitor electrodes.