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

Abstract We report the photocatalytic efficiency of CuO nanowires covered with a thin TiO 2 film, studied by dyes degradation in water. The CuO nanowires were synthesized on Cu foils by thermal oxidation. A subsequent TiO 2 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 TiO 2 /CuO heterojunction. The two semiconductors are in intimate connection increasing the exposed surface and only TiO 2 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 TiO 2 /liquid and therefore to modulate cationic/anionic dyes photo-degradation in water.