Supercapacitance of polypyrrole/titania/polyaniline coaxial nanotube hybrid

The polypyrrole/titania/polyaniline (PPy/TiO2/PANI) coaxial nanotube hybrid has been prepared through a stepwise electrodeposition process for an electrochemical energy storage. Independent TiO2 nanotube array was used as the framework, which was formed by anodizing titanium foil at 30 V in fluoride-containing water and ethylene glycol mixture solution. The PPy was selectively coated on the outer surface of TiO2 nanotube walls to form PPy/TiO2 through a normal pulse voltammetry electrodeposition process. The PANI was then coated on the inner surface of TiO2 nanotube walls to form PPy/TiO2/PANI coaxial nanotube hybrid through a photoassisted cyclic voltammetry electrodeposition process. The morphology and microstructure feature of PPy/TiO2/PANI were characterized by field-emission scanning electron microscopy and Raman spectrum. The capacitance performance was conducted by cyclic voltammetry and galvanostatic charge–discharge measurements. PPy/TiO2/PANI coaxial nanotube hybrid with P/N-type doping properties exhibited a high specific capacitance of 497 F g−1 at a current density of 0.5 A g−1 and a potential window of −0.2 to 0.8 V in 1.0 M H2SO4 solution. The capacitance declined from 267.9 to 193.7 F g−1 after 500 cycles at a high current density of 2.0 A g−1, showing 72.3% capacitance retention and a good cycle stability for the promising supercapacitor application.