Photodegradation under UV light irradiation is a major drawback in photocatalytic applications of sulfide semiconductors. ZnS nanoparticles were doped with very low amounts of chloride or cobalt ions in the ppm range and codoped with chloride and cobalt ions during their synthesis by precipitation in low-temperature zincblende phase annealed at 400 degrees C was found to be stable. annealed at 800 degrees C had a high susceptibility to IN irradiation in water, while the doping led to a stabilization of the ZnS nanoparticles. Based on photochemical and Chlorine doping increased the rate of photocorrosion in water, whereas cobalt aqueous solution followed by calcination. The high-temperature wurtzite phase spectroscopic investigations applying UV/vis, X-ray photoelectron, and photoluminescence spectroscopy, the increased susceptibility of Cl-doped ZnS is ascribed to a higher number of surface point defects, whereas the stabilization by Co2+ is caused by additional recombination pathways for the charge carriers in the bulk, thus avoiding photocorrosion processes at the surface. Additional doping of Cl-doped ZnS with cobalt ions was found to counteract the detrimental effect of the chloride ions efficiently.