Selective photocatalytic degradation of organic pollutants by CuxS/ZnO/TiO2 heterostructures

Abstract

Photoactive heterostructures containing CuxS/ZnO/TiO2 have been obtained by spray pyrolysis deposition followed by post-deposition thermal treatment. The ZnO middle layer morphology was tailored by using chemical additives during the deposition. The samples have crystalline structure with average crystallite size around 80 Å for metal oxides and 90 Å for CuxS. The roughness varies from 27.5 nm for CuxS/dZnO/TiO2 to 33.6 nm for CuxS/pZnO/TiO2 samples. The wettability properties were tested based on the contact angle measurements. The highest surface energy value (106.4 mN/m) corresponding to CuxS/pZnO/TiO2 with 30 min UV irradiation, with a predominant polar component of 85.3 mN/m. The photocatalytic efficiency under UV–Vis light irradiation was evaluated using methylene blue and phenol as pollutants. The highest photocatalytic values (93.4% for methylene blue and 72.3% for phenol) were obtained for CuxS/pZnO/TiO2 heterostructure with successive 30 min UV irradiation at 2 h intervals. The mineralization efficiency was tested using total organic carbon analysis and the results are slightly lower compared with photocatalytic efficiency.