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

Abstract To investigate the original reasons of the remarkable difference of the photocatalytic activity of plasma sprayed TiO 2 and TiO 2 –Fe 3 O 4 coatings, the photoelectrochemical characteristics of plasma sprayed TiO 2 and TiO 2 –Fe 3 O 4 electrodes were examined. The photo-response of the sprayed TiO 2 electrode was comparable to that of single crystal TiO 2 , but the breakdown voltage was approximately 0.5 V (vs. SCE). The short-circuit current of TiO 2 was 1.05 mA/cm 2 , which was 15 times comparing with that of TiO 2 –Fe 3 O 4 electrode under 30 mW/cm 2 xenon light illumination. N-type TiO 2 semiconductor particle reacted with Fe 3 O 4 or Fe 2 O 3 particle and concurrently produced p-type FeTiO 3 in plasma spraying process. FeTiO 3 compound obviously improved the photocatalytic activity of the TiO 2 coating for the formation of p-n junction between p-type FeTiO 3 and n-type TiO 2 , 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.