Poultry litter-derived biochar for supercapacitor applications

Abstract

This research focused on the detailed analytical characterization of the poultry litter-derived biochar followed by its conversion into electrodes for supercapacitor application. Biochar was prepared from poultry waste by pyrolysis at 600 °C for 3 hours and activated it by mixing with potassium hydroxide and re-pyrolyzed at the same temperature for 1 hour. Both the biochar and activated biochar were analyzed using Scanning Electron Microscopy (SEM), Infrared spectroscopy (IR), Time of Flight – Secondary Ion Mass Spectroscopy (ToF-SIMS), and X-ray Photoelectron Spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyses. SEM analyses suggested that the biochar’s surface became more porous and homogeneous after activation with potassium hydroxide. The specific surface area of biochar increased by more than 200 folds to 814 m² g⁻¹ after KOH-activation confirmed from BET analysis. IR indicated the activated biochar contained sulfur- and phosphorous-functional groups but few or no oxygen-functional groups. The decrease in oxides of nitrogen, sulfur, and phosphorous was also observed in ToF-SIMS analysis. In spite of the decrease of oxides, the surface oxygen concentration (at%) increased from 42.3% to 46.6% after activation and was assumed to be present as C-O corroborated by XPS. The specific capacitance of activated biochar calculated from galvanostatic charge-discharge is 152 F/g attributed to its hierarchical porosity, heteroatoms presence, and hydrophilicity. This research is expected to contribute towards the sustainable management of agricultural wastes.