Deposition of ZnS dots onto nanosheets of cobalt-doped ZnO–Zn(OH)2 and their photocatalytic activity

Abstract

In this work, the photocatalytic activity (PCA) of ZnO–Zn(OH)2 nanosheets (NSs) was enhanced by doping with Co and coupling with ZnS, in various ratios of both. XRD, TEM, HRTEM, EDX, DRS, and BET techniques were applied for characterization of the prepared nanocomposites. The PCA was examined by the photodegradation of Methylene Blue. Irradiation was done by UV instead of visible light, to investigate the charge carriers mobility and migration. The pseudo-first-order kinetics show that PCA of {ZnO–Zn(OH)2}:Co/ZnS is higher than those of ZnO–Zn(OH)2, {ZnO–Zn(OH)2}:Co, and {ZnO–Zn(OH)2}/ZnS by 4.8, 1.8, 1.5 times, respectively. Doping with Co makes Zn(OH)2 more UV sensitive, and increases the charge-carriers mobility and crystal conductivity of ZnO and Zn(OH)2. Besides, coupling ZnS with {ZnO–Zn(OH)2}:Co produces type-II heterojunction of ZnS with each of ZnO:Co and Zn(OH)2:Co. This heterojunction saves the charge carriers from recombination for the photocatalytic functionality.