A Fe2(SO4)3-assisted approach towards green synthesis of cuttlefish ink–derived carbon nanospheres for high-performance supercapacitors

The conversion of renewable biomass resources into advanced electrode materials through green, simple, and economical methods has become an important research direction in energy storage. In this study, Fe-decorated N/S-codoped porous carbon nanospheres have been successfully fabricated from cuttlefish ink through Fe2(SO4)3-assisted hydrothermal carbonization coupled with heat treatment. The effects of Fe2(SO4)3 dosage on the structure, chemical composition, and capacitive property of carbon nanospheres were investigated. Herein, environmentally friendly Fe2(SO4)3 plays a multifunctional role as the graphitization catalyst, dopant, and morphology-regulating agent. Benefitting from the moderate graphitization degree, great heteroatom content and hierarchical porous structure, the prepared carbon nanospheres exhibit high specific capacitance (311.9 F g−1 at a current density of 0.5 A g−1), good rate capability (19.1% decrease in specific capacitance as current density increases from 0.5 to 10 A g−1), and ideal cycling stability (94.3% capacitance retention after 5000 cycles). In addition, the symmetric supercapacitor assembled with the carbon nanosphere electrodes achieves an energy density of 9.7 Wh kg−1 at a power density of 0.25 kW kg−1 and maintains 91.3% capacitance after 10,000 cycles. The desirable electrochemical performance of cuttlefish ink–derived carbon nanosphere material makes it a potential electrode candidate for supercapacitors.