Facile fabrication of hierarchical α-Fe₂O₃: Self-assembly and Its magnetic and electrochemical properties

We report novel fabrication of various surface-structure-controlled morphologies of α-Fe₂O₃ in a simple thermal decomposition process. Ferric nitrate-oxalic acid complex formed in ethanol solvent facilitates chain- and rodlike morphological hematites after thermal evaporation of solvent followed by decomposition at 400 °C. This simple methodology offers industrially applicable nanostructured hematite preparation. The oxalic acid concentration and method of solvent evaporation played an important role in the final morphology. Increasing the oxalic acid concentration from 0.125 to 0.4 M facilitated hematite chainlike morphology of porous aggregates. Thermal decomposition temperature played an important role on the surface structure of hematite. The synthesized hematite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectra, Fourier transform infrared spectra (FTIR), and nitrogen adsorption analysis. The influence of various solvents such as ethanol, methanol, propanol, t-butanol, and various iron precursors on the final morphology was investigated, and the results indicated that both solvents and iron precursors are crucial for the final hematite morphology. The magnetic properties of the synthesized chainlike hematite were studied, and the remnant magnetization and coercivity of the chainlike α-Fe₂O₃ at 300 K are found to be 1.36 emu/g and 147 Oe, respectively. The electrochemical Li ion battery performance of synthesized hematite was investigated. A plausible mechanism of hematite self-assembly was proposed.