Microporous TiO2-WO3/TiO2 films with visible-light photocatalytic activity synthesized by micro arc oxidation and DC magnetron sputtering

This study reports the preparation of microporous TiO2-WO3/TiO2 films with a high surface area using a two-step approach. A porous WO3/TiO2 template was synthesized by oxidizing a titanium sheet using a micro arc oxidation (MAO) process. This sheet was subsequently overlaid with a visible light (Vis)-enabled TiO2 (N,C-TiO2) film, which was deposited by codoping nitrogen (N) and carbon (C) ions into a TiO2 lattice using direct current magnetron sputtering. The resulting microporous TiO2-WO3/TiO2 film with a 0.38-μm-thick N,C-TiO2 top-layer exhibited high photocatalytic activity in methylene blue (MB) degradation among samples under ultraviolet (UV) and Vis irradiation. This is attributable to the synergetic effect of two-step preparation method, which provides a highly porous microstructure and the well-crystallized N,C-TiO2 top-layer. This is because a higher surface area with high crystallinity favors the adsorption of more MB molecules and more photocatalytic active areas. Thus, the microporous TiO2-WO3/TiO2 film has promising applications in the photocatalytic degradation of dye solution under UV and Vis irradiation. These results imply that the microporous WO3/TiO2 can be used as a template of hybrid electrode because it enables rapid fabrication.