New approach to enhance the photocatalytic activity of plasma sprayed TiO2 coatings using p-n junctions

To investigate the original reasons of the remarkable difference of the photocatalytic activity of plasma sprayed TiO2 and TiO2-Fe3O4 coatings, the photoelectrochemical characteristics of plasma sprayed TiO2 and TiO2-Fe3O4 electrodes were examined. The photo-response of the sprayed TiO2 electrode was comparable to that of single crystal TiO2, but the breakdown voltage was approximately 0.5 V (vs. SCE). The short-circuit current of TiO2 was 1.05 mA/cm(2), which was 15 times comparing with that of TiO2-Fe3O4 electrode under 30 mW/cm(2) xenon light illumination. N-type TiO2 semiconductor particle reacted with Fe3O4 or Fe2O3 particle and concurrently produced p-type FeTiO3 in plasma spraying process. 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. From these investigations, a promising approach for manufacturing high performance photocatalytic coating by plasma spraying is suggested. (C) 2003 Elsevier B.V. All rights reserved.