Dependence of photocatalytic activity on the compositions and photo-absorption of functional TiO_2-Fe_3O_4 coatings deposited by plasma spray

摘要

Owing to the much concern with global environmental issues, Fe_3O_4 added photocatalytic TiO_2 coatings were deposited using plasma spray for environmental depollution. The influence of the content of Fe_3O_4 additive to the TiO_2 powder on the phase composition, microstructure and photo-absorption of plasma-sprayed TiO_2 coatings was systematically studied. The results showed that the TiO_2-Fe_3O_4 coatings consisted of anatase TiO_2, rutile TiO_2 and Fe_2TiO_5 pseudobrookite phase which appeared when the content of Fe_3O_4 additive was equal to or over 10%. The content of FeTiO_3 was highest in the sprayed TiO_2-10%Fe_3O_4 coatings. The addition of Fe_3O_4 improved the anatase-rutile transformation of TiO_2-Fe_3O_4 powders. Furthermore, it was found that TiO_2 coatings can decompose acetaldehyde under the illumination of ultraviolet rays, and the degrading efficiency was improved with an increase of FeTiO_3 content in the coatings. A two-step electron transfer model was proposed to explain the good photocatalytic activity of the sprayed coating with high content of FeTiO_3. However, presence of large amount of Fe_2TiO_5 compound substantially reduced the photocatalytic efficiency of the sprayed TiO_2-Fe_3O_4 coatings for its unfavorable photo-excited electron-hole transfer process.