Yerba mate: From waste to activated carbon for supercapacitors

Developing technological solutions that use yerba mate waste as precursors is key to reducing the environmental impact caused by the lack of treatment and its accumulation in landfills. Due to their physicochemical properties, these residues can be used to develop activated carbons. Activated carbon is a versatile material with a high surface area that can be used for energy storage. In this work, yerba mate residues were valued by producing chemically activated carbon to be used as electrode material in supercapacitors. Activated carbons were developed through chemical activation in two steps with KOH. Variables such as impregnation ratio and activation temperature are studied. The developed carbons were characterized by physicochemical and electrochemical techniques. They were found to have high surface areas, up to 1800 m² g^-1, with a hierarchical porous distribution. A maximum specific capacitance of 644 F g^-1 at 0.1 A g^-1, and power values of ca 32,000 W kg^-1, at 33 A g^-1 were found. All the synthesized carbons have excellent electrochemical properties and are suitable for use as active material in supercapacitors.