Fabrication of hybrid supercapacitor of RGO//PPyNTs/Co(OH)(2) based on K3Fe(CN)(6) redox-active electrolyte

High power density and long cycle life make supercapacitor attractive in the energy storage field, but low energy density is still an urgent issue to be addressed. Introducing redox active substances to electrolyte can enhance the energy density due to their contribution of additional psuedocapacitance. Herein, polypyrrole nanotubes (PPyNTs), as templates, are covered by cobalt hydroxide (Co(OH)(2)) to fabricate PPyNTs/Co(OH)(2) nanocomposite. In 2 mol L-1 KOH electrolyte, the specific capacitance of PPyNTs/Co(OH)(2) is only 838 F g(-1), but with 0.1 mol L-1 K3Fe(CN)(6) added, the specific capacitance can reach 4322 F g(-1) at a current of 1 A g(-1). In addition, the coulombic efficiency is 456%, which is more than five-fold of the original that of 96%. Furthermore, at a current of 1 A g(-1), RGO//PPyNTs/Co(OH)(2) hybrid supercapacitor exhibits a specific capacitance of 96.12 F g(-1) and the energy density of 38.58 Wh kg(-1) under a power density of 800 W kg(-1). Undoubtedly, with the help of K3Fe(CN)(6), the device not only increases cycling stability from73.5% to 95.0% after 5000 cycles but also easily illuminates three LED.

Automated summary

In this study, a nanocomposite of polypyrrole nanotubes and cobalt hydroxide was fabricated to enhance the specific capacitance by adding K3Fe(CN)(6), leading to increased energy density. The hybrid supercapacitor demonstrated good cycling stability and power performance.