Achieving enhanced blue-light-driven photocatalysis using nanosword-like VO2/CuWO4 type II n-n heterojunction

New nanosword-like (NSs) n-n type II heterojunction with energy band gap of 1.75 eV was prepared by composing n-type VO2 and n-type CuWO4 compounds (n-VO2/n-CuWO4-NSs) and subsequently characterized by FT-IR, EDS, XRD, FESEM, UV-Vis-DRS and PL spectroscopy. The n-VO2/n-CuWO4-NSs were efficiently used as blue-light-driven type II photocatalyst for the simultaneous degradation of cationic azure II and auramine O dyes. The studies of OH generation on the VO2/CuWO4-NSs under blue light irradiation showed that high amount of surface-generated OH can be transferred to OH−, while photo-excited electrons of the valence band could oxidize organic pollutants in water. The catalytic activity of VO2/CuWO4-NSs for the simultaneous photodegradation of AZ II and AO was followed in mild conditions without additional oxidation agents. Several experiments were designed by central composite design where parameters including irradiation time, pH, VO2/CuWO4-NSs mass as well as AZ II and AO concentrations involved in the process were optimized. The significance of individual parameters and their possible interactions was investigated using the analysis of variance. The optimum values of 80 min, 6, 0.02 g, 8 and 4 mg/L were obtained for the irradiation time, pH, VO2/CuWO4-NSs mass and the initial concentrations of AZ II and AO, respectively, with desirability of 0.70. At such condition, the photodegradation percentages of AZ II and AO were found to be 83.8 and 70.2%, respectively.