Leather Waste-Derived Biochar with High Performance for Supercapacitors

Activated biochars from solid residues have been very successful in many applications due to their high surface area, porosity properties, and surface chemistry. Our work, leather waste-derived biochar obtained from pyrolysis of footwear leather wastes at 700°C, followed by a chemical activation with KOH has been prepared, and characterized by SEM, physisorption, XPS and Raman. Results showed that activation with KOH increases the biochar BET specific surface area by almost 100 times. The biochars were tested as electrode materials for supercapacitors in four different aqueous electrolytes, where the KOH activated biochar (AL700) shows higher capacitances. A maximum specific capacitance of 268 Fg-1 (5 mVs-1) was obtained in 0.5M H2SO4 electrolyte for the AL700. A supercapacitor cell was assembled showing excellent performance, with a capacitance of 52 Fg-1 at 0.5 mA g-1 with only 8% of capacitance loss after 5000 charge/discharge cycles, reveling a high stability. The maximum specific energy and specific power determined were 12.8 Wh kg-1 and 1.8 kW kg-1, respectively. These results indicate that it is possible to use the footwear leather waste in energy storage devices, such as in supercapacitors showing a major improvement in SC cells performance, compared to commercial carbons.