TiO2 coated CuO nanowire array: Ultrathin p-n heterojunction to modulate cationic/anionic dye photo-degradation in water

We report the photocatalytic efficiency of CuO nanowires covered with a thin TiO2 film, studied by dyes degradation in water. The CuO nanowires were synthesized on Cu foils by thermal oxidation. A subsequent TiO2 deposition (7, 15, 30, 50 nm thick) was performed by atomic layer deposition, developing an ultrathin p-n heterojunction. A structural characterization was obtained by X-ray diffraction analysis, scanning and transmission electron microscopies equipped with energy dispersive x-ray analysis. The photocatalytic activity of the investigated materials was tested by the degradation of a cationic (methylene blue) or anionic (methyl orange). The relevance of the reported results was discussed in relation with the effects of the ultrathin p-n TiO2/CuO heterojunction. The two semiconductors are in intimate connection increasing the exposed surface and only TiO2 is directly in contact with water. This allowed to study systematically the effect of the electric filed generated by the p-n junction on the interface TiO2/liquid and therefore to modulate cationic/anionic dyes photo-degradation in water. (C) 2017 Elsevier B.V. All rights reserved.