Carbon Nanofibers as Supporting Substrate for Growth of Polyaniline Nanorods on FeO Nanoneedles toward Electrochemical Energy Storage.

Iron-oxide (FeO) nanoneedles were first in situ grown on the surface of carbon nanofibers (CNFs) using hydrothermal and N annealing process, and then polyaniline (PANI) was coated on the FeO nanoneedles to form network-like nanorods through dilute solution polymerization. The PANI/FeO/CNFs binder-free electrode exhibited a high specific capacitance of 603 F/g at 1 A/g with good rate capability. (The capacitance loss was about 48.3% when the current density increased from 1.0 to 5.0 A/g.) It was caused by the fact that the PANI/FeO/CNFs with a well-connected structure could provide a continuous electron transport path and improve the conductivity of the entire electrode. The solid-state hybrid PANI/FeO/CNFs∥PANI/FeO/CNFs symmetric device also achieved a high energy density of 29.85 Wh/kg at a power density of 500 W/kg. This universal compatible synthetic method for the PANI/FeO/CNFs electrode could extend to other supercapacitor electrode systems, making it easy to fabricate various ternary electrodes for supercapacitors.