Photocatalytic behavior of nickel and silver doped ZnS nanoparticles: Reassessing the role of metal dopants

This study explores the synthesis, characterization, and photocatalytic performance of metal sulfide nanomaterials, specifically ZnS, Zn 0.95 Ni 0.05 S, and Zn 0.95 Ag 0.05 S, with an emphasis on the impact of transition metal doping on their photocatalytic efficiency. Utilizing the sol-gel method, we synthesized these nanomaterials and employed various advanced techniques to analyze their properties. X-ray diffraction (XRD) analysis revealed alterations in lattice parameters and crystallite sizes due to doping, while Fourier-Transform Infrared Spectroscopy (FTIR) validated the chemical composition. Diffuse Reflectance Spectroscopy (DRS) indicated enhanced light absorption in the doped samples. A photoluminescence (PL) spectrometer was employed to further investigate the optical behavior of the nanocatalyst. Specific surface area, porosity, morphological and compositional details were provided by Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). Photocatalytic performance was assessed by testing the degradation of Methylene Blue (MB), a model organic pollutant. Our results showed that the pure ZnS nanoparticles achieved the highest degradation rates, outperforming the doped variants. This study uniquely reports that common dopants such as Ni and Ag may negatively impact charge carrier utilization in ZnS, contradicting assumptions in existing literature. Thus, although doping can modify structural and optical properties, pure ZnS remains the most effective photocatalyst for environmental applications, emphasizing the need for careful optimization in doping strategies. • Successful synthesis of transition metal doped ZnS nanocrystals using the sol-gel method. • Transition metal doping altered crystallite size, lattice structure, and light absorption. • BET analysis revealed a significant reduction in surface area upon Ni and Ag doping. • Doping improved visible light absorption but introduced recombination centers. • Findings emphasize the trade-off between light harvesting and charge separation.