Electrodeposition of Amorphous Fe2 O 3 Films by Reduction of Iron Perchlorate in Acetonitrile

Electrodeposition of amorphous films of nanometer size was performed by reduction of or in oxygenated acetonitrile. Cyclic voltammetry has shown that the oxide‐film formation occurs via oxidation of electrodeposited metal by dissolved oxygen. The oxide films were characterized by cyclic voltammetry, electrochemical quartz crystal microbalance, X‐ray diffraction, and UV‐visible spectroscopy. The films are reversibly reduced in in two redox processes to the and FeO oxides via lithium intercalation. The UV‐visible (UV‐vis) spectrum displays absorption with an optical gap (1.75 eV) characteristic of amorphous . Spectroelectrochemistry has shown that reduction causes bleaching of the yellowish films (electrochromic efficiency at 400 nm). Heating the films at 500 °C converts them to the crystalline α‐Fe2O3 form with loss of electroactivity.