Human Hair-Derived Porous Activated Carbon as an Efficient Matrix for Conductive Polypyrrole for Hybrid Supercapacitors

The electric double layer capacitor (EDLC) mechanism offered by carbon frameworks alone cannot suffice the unprecedented demand for energy. Hence, including a pseudocapacitive material (conducting polymer) in the carbon framework can impart additional pseudocapacitance to the material, thereby improving its electrochemical performance. Herein, human hair as a biowaste resource with inherent heteroatoms has been subjected to chemical activation at 800 degrees C to yield human hair-derived activated carbon (HHAC). Sub-sequently, an in situ chemical oxidation technique has been employed to generate the composite of HHAC and polypyrrole (HHAC/PPy). The HHAC/PPy composite when tested in 1 M H2SO4 outperforms pristine HHAC and PPy, with a higher specific capacitance of 358 F/g compared to 274 and 53 F/g obtained for individual materials, respectively (at 0.5 A/g). Moreover, the HHAC/PPy composite also solved the problem of low cyclic stability in the conducting polymers by maintaining 84.2% of the initial capacitance after 5000 charge-discharge cycles. In addition, a HHAC/PPy//HHAC asymmetrical supercapacitor device was assembled in an aqueous electrolyte (1 M H2SO4), which delivered an ultrahigh energy density of 53.3 W h/kg with a respectable power density of 408.5 W h/kg that can help in avoiding costly and toxic organic electrolytes. Our study achieved an electroactive carbon material with the synergy of both EDLC and pseudocapacitance materials, which has great potential for supercapacitor applications.

Automated summary

The combination of activated carbon derived from human hair and conducting polymer (polypyrrole) as a composite material shows enhanced pseudocapacitance, higher specific capacitance, and improved cyclic stability for supercapacitor applications. An assembled asymmetrical supercapacitor device using the composite material exhibits a high energy density and power density in an aqueous electrolyte, avoiding the need for expensive and toxic organic electrolytes.