Effectively Improving Capacitive Performance of Three‐Dimensional Iron(III) Oxide Nanotube Arrays by Rationally Filling Mesopores with Polypyrrole

Fe2O3 is a promising electrode material for electrochemical capacitors (ECs), but the challenge remains in enhancing its capacitive performance. Here we effectively improve the capacitive properties of 3D Fe2O3 nanotube arrays by partly filling their mesopores with polypyrrole (PPy) via vapor-phase polymerization. Although the filled PPy is only 9.7 wt%, the resulting hybrid Fe2O3/PPy arrays triple the specific capacitance to 367 F g−1 at 1.0 A g−1, double their high rate capability (106 F g−1 at 10 A g−1) and exhibit good cycling stability at high current density. The results are one of the best capacitive performances among the Fe2O3-based electrodes. It is believed that partly filled mesopores not only increase the electronic conductivity and electroactivity of each hybrid nanotube, but also avoid the blocking of diffusion path for ion. All the features allow the arrays to exhibit synergetic pseudocapacitive properties, and to keep stable and fast electrochemical kinetics. Our findings provide an efficient strategy to boost the electrochemical performances of transition metal oxide nanomaterials by rationally filling their mesopores with small amount of conductive polymer.