Preparation and Supercapacitor Performance of Freestanding Polypyrrole/Polyaniline Coaxial Nanoarrays

The flexible, freestanding polypyrrole/polyaniline (PPy/PANI) coaxial nanoarray was prepared by removing a titania (TiO2) sacrificial template from PPy/TiO2/PANI, which was initially formed by selectively coating PPy and PANI on the outer and inner surfaces of individual TiO2 nanotubes. PPy/PANI formed a hybrid coaxial structure of PANI nanorods encased in PPy nanopores. The PPy/PANI coaxial nanoarray exhibited a specific capacitance of 209.5 Fg(-1) at 0.5 Ag-1, presenting higher performance than the PPy nanopore array (114.2 Fg(-1)). Its capacitance decreased from 157.5 to 125.2 Fg(-1) after 500 cycles at 2.0 Ag-1, presenting a reasonable capacitance retention of 79.5%. The flexible supercapacitor based on the PPy/PANI coaxial nanoarray demonstrated a specific capacitance of 66 Fg(-1) at 0.5 Ag-1. The PPy/PANI coaxial nanoarray exhibited high pseudocapacitance, moderate cyclibility, and good flexibility, suggesting its promising application in flexible energy storage devices.