Rapid electroplating of photocatalytically highly active TiO2-Zn nanocomposite films on steel

Abstract

Nanocomposite films consisting of TiO₂ and Zn with thickness of 10–15 μm (TiO₂-Zn) have been electrodeposited on steel plates by rapid plating from a ZnSO₄-based bath (I _d > 10 A dm⁻²). Upon addition of NH₄NO₃ to the bath (<0.3 g L⁻¹), the uptake of TiO₂ in the film significantly increased. Glow discharge optical emission spectrometry clarified that TiO₂ particles were incorporated throughout the film and the loaded amount increased near the surface. The first-order rate constant (k/h⁻¹) for gas-phase CH₃CHO oxidation was employed as an indicator of the photocatalytic activity. The k value for the TiO₂-Zn film prepared at I _d = 12 A dm⁻² (0.20 h⁻¹) was comparable to that for the sample from a ZnCl₂-based bath at I _d = 4 A dm⁻² (0.27 h⁻¹). X-ray diffraction measurements indicated that a TiO₂-ZnO nanocomposite layer was generated on the surface by the heat treatment in air at 673 K for 6 h. Consequently, the photocatalytic activity was further improved (k = 0.29 h⁻¹); this effect was explained in terms of the synergy of TiO₂ and ZnO in photocatalysis.