Boosting the energy storage performance with human hair-derived reduced keratin

This investigation explores the potential use of keratin derived from human hair-a common bio-waste material-as a capacitive element that can deliver significant energy density in pseudocapacitors. The keratin was chemically reduced and extracted from untreated human male hair, producing a high-quality material. This method is related to a patent application (TR 2023/002929 B). The electrical conductivity of keratin has not been thoroughly examined and remains a topic of debate. While some studies suggest high conductivity under certain conditions, others point out inherent limitations. This study addresses these discrepancies by fabricating supercapacitor devices and evaluating their impedance and current-voltage characteristics under specific design parameters. The developed symmetric supercapacitor device, featuring a glass fiber separator and 6 M KOH electrolyte, exhibited impressive capacitance (800 F/g) and energy density (111.1 Wh/kg) without compromising power efficiency. These favorable capacitance values indicate exceptional charge-discharge properties of the device. Advanced techniques, particularly NMR and EPR spectroscopies, provided significant insights that had not been reported previously. These methods enabled regulation of the electron-transfer mechanism, thereby enhancing our understanding of the relationship between material properties and device performance. NMR and EPR analyses revealed the presence of carbon-based defects or radicals, enabling precise control over defect structures and correlating them with the device's superior performance.