Synthesis of Hierarchical Iron Oxide Nanotube/Nickel Foam Electrodes for Supercapacitors
Yu-Hsueh Chang1*, Yu-Chang Lin1,2, Liang-Ching Hsu1, Po-Yang Peng1, Yan-Gu Lin1
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan
* presenting author:Yu-Hsueh Chang,
An iron-oxide (Fe2O3) nanotube (NT) array is grown directly as a hierarchical nanoarchitecture on a nickel-foam (NF) surface via a simple and cost-effective immersive process. The morphology and microstructure of Fe2O3 NT arrays are systematically examined by scanning electron, transmission electron, Raman, and X-ray photoelectron spectroscopies. The results reveal that the walls of Fe2O3 NT are composed mainly of agglomerated small α-Fe2O3 (hematite) monocrystalline nanoparticles filled with a few ZnO monocrystalline particles. The microstructural influence on the pseudocapacitive performance of the obtained Fe2O3 NT/NF electrodes is also investigated via in-situ X-ray absorption spectroscopy (XAS) and electrochemical measurement. The in-situ XAS results regarding charge storage mechanisms of the Fe2O3 NT/NF electrodes show that a Li+ can reversibly insert/desert into/from the 3D mesoporous textures between the Fe2O3 subunits depending on the applied potential. The electrochemical results indicate that the Fe2O3 NT/NF electrode shows highly reversible features and satisfactory rate abilities. Most significantly, the excellent specific capacitance achieved in Fe2O3 NT/NF nanoelectrodes is as great as 300.1 F g-1 ; energy density 75Wh kg-1 and power density 4.5 kW kg-1 are obtained, and the Fe2O3 NT/NF nanoelectrode has acceptable cycling stability after 3000 cycles.

Keywords: iron oxide, nanotubes, chemical synthesis, electrochemical, supercapacitor