Methyl orange as self-degraded template to fabricate the crystalline tetragonal hollow polyaniline nanotubes for all-solid-state flexible supercapacitors

It is found that methyl orange can be effectively self-assembled into the aggregation of rigid rod to form rectangular template for the growth of PANI and then an uncomplicated one-step self-degraded template method has been used to prepare uniform crystalline tetragonal hollow polyaniline (PANI) nanotubes. The inner and outer surfaces of PANI nanotubes are completely exposed to the electrolytes due to the large inner diameter of PANI nanotubes, which can enhance the utilization efficiency of the electrode materials, resulting in a high specific capacitance up to 590 ± 36 F/g at a scan rate of 5 mV/s. Furthermore, the enhanced specific capacitance and rate capability can be explained by the nearest neighbor regular folded-chain model. The symmetric all-solid-state flexible supercapacitor device is also assembled by PANI nanotubes electrodes to form the sandwich structure, and the maximum energy density is 14.56 Wh/kg at a power density of 250 W/kg. Considering the low cost and convenient preparation of PANI, the tetragonal hollow PANI nanotubes are expected to play an important role in the application of supercapacitors.