ELECTRODEPOSITION OF AMORPHOUS FE2O3 FILMS BY REDUCTION OF IRON PERCHLORATE IN ACETONITRILE

Electrodeposition of amorphous Fe2O3 films of nanometer size was perfo rmed by reduction of Fe(ClO4)(3) or Fe(ClO4)(2) in oxygenated acetonit rile. Cyclic voltammetry has shown that the oxide-film formation occur s via oxidation of electrodeposited metal by dissolved oxygen. The oxi de films were characterized by cyclic voltammetry, electrochemical qua rtz crystal microbalance, X-ray diffraction, and UV-visible spectrosco py. The films are reversibly reduced in acetonitrile + LiClO4 in two r edox processes to the Fe3O4 and FeO oxides via lithium intercalation. The UV-visible (UV-vis) spectrum displays absorption with an optical g ap (1.75 eV) characteristic of amorphous Fe2O3. Spectroelectrochemistr y has shown that reduction causes bleaching of the yellowish films (el ectrochromic efficiency congruent to 30 C-1 cm(2) at 400 nm). Heating the films at 500 degrees C converts them to the crystalline alpha-Fe2O 3 form with loss of electroactivity.