Di-oxidant sandwich-type polymerization strategy of polypyrrole on CNTs@wool felt for supercapacitors

Abstract Optimization of mass loading and intrinsic structure of polypyrrole (PPy) materials plays decisive roles in the development of energy storage systems to meet the increasing requirements. A di-oxidant sandwich-type polymerization (designated as DOSP) method was developed to synthesize PPy on the surface of CNTs@wool felt to construct composites (CNTs/PPy-2@wool) by using FeCl3∙6H2O and MnO2 as di-oxidant. Under acidic conditions, MnO2 acts as both a sacrificial template and oxidant to initiate the polymerization of pyrrole (Py) monomers on its freshly activated surface to obtain CNTs/PPy-2@wool. Furthermore, MnO2 could effectively adsorb Py monomers, and the adsorbed Py monomers were oxidatived to PPy, resulting in the efficient adsorption and high mass loading of PPy (13.44 mg cm−2) on the CNTs@wool felt surface. As a result, the CNTs/PPy-2@wool electrode showed an areal capacitance of 2303.9 mF cm−2 at a current density of 0.25 mA cm−2 in 1 M H2SO4 solution, delivering a max energy density of 204.79 μWh cm−2 at a power density of 457.93 μW cm−2. Moreover, the device exhibited good rate capability with capacitance retentions over 65% when the current density increased from 0.25 mA cm−2 to 2 mA cm−2 and a long-term life with 84.29% of initial capacitance after 1000 cycles. The potential application of the proposed CNTs/PPy@wool felt as electrode materials for various integrated energy storage devices.