Electrochemical Study of the Electrodeposition of a Dense Nanocrystalline Fe Film from Fe(II) Ions Dissolved in an Ionic Liquid

The electrodeposition behavior of Fe was studied in phenyltrimethylammonium chloride-ethylene glycol eutectic-based ionic liquids (TMPAC-EG EILs) containing FeCl2 through electrochemical measurement and the deposit characterization. Some kinetic parameters (standard rate constants, transfer coefficients and activation energy for standard rate constants) as well as transport properties were obtained and discussed as function of temperature. The values of transfer coefficient (0.32–0.39) are significantly lower than conventional value (0.5). Electrodeposition of Fe follows three-dimensional progressive nucleation and growth mode, which is unaffected by temperature. Besides, it is found that deposition temperature plays a central role in controlling surface morphology and structure of the resultant Fe coatings. At low temperature (333–353 K), smooth and dense iron coating can be obtained. The phase structure changes from a nanocrystalline α-Fe to amorphous phase (metallic glass) as the deposition temperature increases from 333 K to 353 K.