Molten Salt Pyrolysis of Melamine‐Modified Denim Fabric Waste into Nitrogen‐Doped Activated Carbon for Supercapacitor Applications

Conversion of biomass waste into nitrogen‐doped porous carbon has been considered as a promising approach to achieve energy storage materials. Nitrogen‐doped activated carbon materials have been successfully prepared by molten salt pyrolysis (MSP) using melamine modified‐denim fabric waste as precursor. The molten salt medium provides liquid condition to carbonize and activate the denim fabric waste. Melamine produces a large amount of nitrogen element for doping the carbon materials. The obtained nitrogen‐doped denim fabric‐based carbon materials (NDFC‐MSP) are composed of small fibrous fragment and thin sheet, and exhibit a high specific surface area (1975.2 m2⋅g−1) and high pore volume (1.087 cm3⋅g−1). Moreover, NDFC‐MSP sample with a high nitrogen content of 6.93 wt.% possesses a maximum specific capacitance of 345.8 F⋅g−1 at 0.25 A⋅g−1 in 6 M KOH electrolyte. It also displays a high specific capacitance of 230 F⋅g−1 at 10 A⋅g−1. The cycle stability shows 95.5% retention after 5000 charge‐discharge cycles at 1 A⋅g−1. In addition, the fabricated symmetric NDFC‐MSP supercapacitor with a wide voltage range of 1.8 V generates a maximum energy density of 17.0 Wh⋅kg−1 at power density of 225 W kg−1 in 1 M Na2SO4 aqueous electrolyte. Denim fabric waste modified with melamine has been successfully converted into nitrogen‐doped carbon materials by molten salt pyrolysis. This method has provided a new protocol for conversion textile solid waste into add‐value carbon materials. The supercapcacitor performance of porous nitrogen‐doped carbon materials can achieve maximum specific capacitance of 345.8 F⋅g−1, and cycling retention of 95.5% with 5000 cycles at 1 A⋅g‐1.