Hydrogen bond enforced polyaniline grown on activated carbon fibers substrate for wearable bracelet supercapacitor

The polyaniline grown on activated carbon fibers (PANI-ACF) was synthesized through an electrochemical deposition process to act as the energy storage electrode material for wearable bracelet supercapacitor application. The ACF was synthesized by activating carbon fibers through hydrothermal process in HNO3 solution and then thermal process in argon atmosphere, which kept the microporous surface structure and oxygen-containing functional groups. The ACF substrate could contributes to improving electrical conductivity and activation of PANI-ACF. The density functional theory calculation result shows that PANI-ACF has larger Fermi energy than PANI. The XPS spectrum measurements and Mulliken charge distribution analysis indicate the formation of interfacial hydrogen bond interaction between hydroxyl group of ACF and amino group of PANI in PANI-ACF. The HOMO-LUMO energy gap decreases from 2.62 eV of PANI to 0.23 eV of PANI-ACF, indicating the bonding interaction is beneficial to improve conductivity of PANI. The PANI-ACF achieves superior capacitance of 296.3 F g−1 at 1.0 A g−1 and maintains reasonable capacitance retention of 63.8 % when the current density increases from 1.0 to 10 A g−1. Electroactive PANI-ACF electrode was applied for wearable bracelet-supercapacitor, which exhibits the energy density of 30.42 Wh kg−1 at power density of 900 W kg−1. So, hydrogen bond enforced PANI-ACF electrode with high capacitance and flexibility properties presents the promising wearable energy storage application.