Charges Generation and Separation in Plasma Sprayed TiO₂-Fe₃O₄ Coatings

TiO₂ based coatings are promising photocatalyst as they are chemically stable and nontoxic. To develop more effective photocatalyst with cost effective plasma spraying technique, TiO₂ and TiO₂-Fe₃O₄ coatings were prepared using agglomerated anatase TiO₂ and composite TiO₂-Fe₃O₄ powders, respectively. The photocatalytic activity and photoelectrochemical characteristics of sprayed coatings were examined. The photo-response of the sprayed TiO₂ electrode was comparable to that of single crystal TiO₂, but the breakdown voltage approximated to 0.5V (vs. SCE). The short-circuit current of TiO₂ was 1.05mA/cm², which was 15 times comparing with that of TiO₂-Fe₃O₄ electrode under 30mW/cm² xenon light illumination. N-type TiO₂ semiconductor particle reacted with Fe₃O₄ or Fe₂O₃ particle and concurrently produced p-type FeTiO3 in plasma spraying processes. FeTiO3 compound obviously improved the photocatalytic activity of the TiO₂ coating for the formation of p-n junction between p-type FeTiO3 and n-type TiO₂, which may spatially separate the photo-generated electrons and holes. As a result, plasma-sprayed TiO₂-Fe₃O₄ coatings are promising candidates for the applications to photocatalyst.