Obtaining and Study of the photocatalytic activity of ZnO-ZnS:Er composites

Abstract ZnO-ZnS:Er composites were synthesized by varying the percentage of erbium (2%, 4%, 6%) in a chemical bath. XRD peaks corresponding to the crystalline phases of ZnO and ZnS were identified, and an average crystallite size of 12 nm was obtained using the Scherrer equation. The optical properties were studied by UV-Vis spectroscopy, observing electronic transfers (2P3/2, 4F3/2, 4F7/2, 4H11/2, 4F9/2, as well as deep levels 4I9/2, 4I11/2) related to erbium. The forbidden bandwidth was calculated with the Tauc equation, presenting Urbach Tails in 3.35 to 3.79 eV. By EDS, the elemental analysis of Zn, O, S and Er was carried out. SEM analyzed the surface morphological change due to the incorporation of Erbium. By FTIR, we found the vibrational groups of OH-, H-O-H, C=O, Zn-Zn-O, and Er-O. By PL from 350 to 700 nm, the types of intrinsic defects such as zinc interstitials (Zni), zinc vacancies (Vzn), oxygen vacancies (Vo), and oxygen vacancies (V++) were observed. The PL intensity increases with 4% Er sample and in 6% Er sample, a shift of the maximum peak from 436 nm to 378 nm was observed, related to the phenomenon of electron recombination. The photocatalytic activity was measured with methylene blue as an organic pollutant, being the 4% doped ZnO-ZnS showing the most photocatalytic activity, degrading 70% of the pollutant in 80 minutes.