 Abstract defect engineering is a method for improving light harvesting in photocatalytic materials like zinc sulfide, ZNS, by introducing defects into the crystal structure through altering the SZN molar ratio during hydrothermal processes. The band structures can be modified and defects formed on the surface which are confirmed using XRD, Raman Studies, Williamson Hall model, size-strain plot, UVVIS doctors, PL, TEM, SEM, ICPOES, and XPS. Defective ZNS with different quantities of ZN and S-poids are used as catalysts to investigate vacancy-dependent photocatalytic activity under exposure to visible light with the lowest SZN sample showing superior activity. This article was authored by Imahamad Jubir, M. Aslam Manframal, P. Asabar, and others.