PREPARATION AND CHARACTERIZATION OF NANOCRYSTALLINE COMPOSITE (NANOCOMPOSITE) FILMS OF TITANIUM-DIOXIDE AND NICKEL BY OCCLUSION ELECTRODEPOSITION

A new family of nanocrystalline composite films was developed for phot oelectrochemical application by occlusion deposition of TiO2 particles from a nickel plating bath. The photoactivity of the resultant Ni\TiO 2 films was examined under chopped-light illumination with a xenon are lamp in 0.1 M KNO3. A TiO2 dose in the nickel bath of 0.8 M, a deposi tion potential of - 0.8 V, a bath pH of 5.0, a bath temperature of 20 degrees C and a film deposition charge of 36mC (corresponding to a fil m ca. 0.7 mu m thick) were found to yield the best photoresponse for t he resultant Ni\TiO2 films. The photoresponse of these nanocomposite f ilms was compared with that of TiO2 layers on Ti supports, obtained ei ther from thermal oxidation of titanium or by oxidative decomposition of aq. TiCl4 at 550 degrees C. Formate and acetate ions were employed as current-doubling agents in the 0.1 M KNO3 electrolyte for this comp arative study. The current-doubling effect was seen to be the highest for the Ni\TiO2 films; possible mechanistic origins for this trend are discussed. Other characterizations of the Ni\TiO2 films, including an alyses by laser Raman spectroscopy and X-ray photoelectron spectroscop y, are also discussed.