Enhanced capacitance of supercapacitors made with activated carbon derived from corn-husk and agave bagasse: A comparative study of activating agents (KOH and H3PO4)

Activated carbons derived from agave bagasse and corn husk (wasted biomass obtained from crop fields) were used as redox powders for supercapacitors (SCAPS) electrodes. Such activated carbon (AC) had a morphology of porous grooves/rods and exhibited amorphous structure. In addition, the carbons were activated with KOH or H 3 PO 4 (HPO) before their use in supercapacitor’s electrodes. SCAPs made with AC derived from agave bagasse and treated with HPO had a capacitance/energy-density of 197.1 F g -1 /39.41 Wh kg -1 . SCAPs made with AC derived from corn husk and treated with HPO had a capacitance/energy-density of 240.2 F g -1 /48 kg -1 , while SCAPs made with AC derived from corn husk and treated with KOH had a superior capacitance/energy-density of and 366.78 F g -1 /73.3 Wh kg -1 , respectively. Thus, those last SCAPs containing AC treated with KOH had 52-85% higher capacitance in comparison with the other two SCAPS. This occurred because the SCAPs containing AC treated with KOH had 22-28% higher surface area in comparison with the other activated carbon. Furthermore, the AC treated with KOH presented higher content of oxygen-vacancy-defects (OVx) in comparison with the other AC (as demonstrated by Raman and UV-Vis spectroscopies). Moreover, only the device containing AC treated with KOH presented redox peaks, those ones appeared due to changes of oxidation states for K and P elements according to XPS measurements. In general, the results of this research indicate that low-cost activated carbons derived from agave bagasse or corn husk are a reliable alternative for the fabrication of efficient supercapacitors. Utilizing such AC promotes sustainability and reduces the contamination of the environment by biomass waste.