Dye wastewater reuse: energy storage strategies for supercapacitors

Supercapacitors have attracted much attention because of their fast charging and discharging characteristics, and the development of high-efficiency carbon materials plays a crucial role in improving the performance and application of supercapacitors. The strategy of “killing two birds with one stone” to achieve dye wastewater treatment and improve the pseudo-capacitance of electrode materials provides an environmentally friendly and cost-effective solution for dye wastewater treatment. This work successfully used a simple one-step hydrothermal method of attaching dye molecules to glucose-derived carbon to treat dye wastewater and effectively used the functional groups in the dye molecules. Moreover, the structural agglomeration caused by hydrothermal carbonation was resolved, and the reticulated dye molecules improved the continuity within the material and provided additional channels for ion transport. The mixture was then annealed with NH₄F at high temperature, and the NH₄F activation introduced nitrogen atoms into the carbon material, increasing the electrical conductivity of the material and etching the surface of the material, increasing the number of active sites on the material. The optimum carbon material has a specific surface area of 727.09 m² g⁻¹, and the percentage of heteroatoms increases from 5.37% to 13.87%, an increase of 158.29%. In a three-electrode system with 6 mol L⁻¹ KOH as the electrolyte and a current density of 0.5 A g⁻¹, the material shows a specific capacitance of 191.5 F g⁻¹ and good multiplicative performance (77.4% capacitance retention after increasing the current to 20 times that of 0.5 A g⁻¹) as well as stability (essentially no change in capacitance after 5000 cycles).

Graphical abstract