OICC Press Iranian Journal of Catalysis 2345-4865 15 1 2025 01 13 Synthesis and Characterization of CdS and Ni-CdS thin Films: an Overview of Photocatalytic Degradation of Methylene Blue Dye 1 11 10.57647/j.ijc.2025.1501.09 EN Rajeshvarsing S. Padavi Nano-Chemistry Research Laboratory, G. T. Patil, Arts, Commerce and Science College, NandurbaR, Maharashtra, India  AND  RFNS, Senior Science College, Sorapada, Akkalkuwa, Maharashtra, India https://orcid.org/0009-0009-1758-9636 Subhash D. Khairnar Nano-Chemistry Research Laboratory, G. T. Patil, Arts, Commerce and Science College, Nandurbar, Maharashtra, India  AND  SSPM's Vasantrao Naik Arts Science and Commerce College Shahada,  Nandurbar, Maharashtra 425412, India. https://orcid.org/0000-0002-6732-366X Vinod S. Shrivastava Nano-Chemistry Research Laboratory, G. T. Patil, Arts, Commerce and Science College, Nandurbar, Maharashtra, India https://orcid.org/0000-0002-2065-1068 Journal Article 2025 01 13 CdS and Ni-CdS thin films were synthesized using the chemical bath deposition technique. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), and energy-dispersive X-ray spectroscopy (EDS). The average crystallite size of both thin films ranged between 1.5 to 4.26 nm, analyzed by the XRD as well as the Williamson-Hall method. The SEM results reveal the nanoflakes-like morphology uniformly distributed over the surface of thin films. The optical band gap was decreased from 2.29 to 2.03 eV when Ni2+ was incorporated into the CdS crystal lattice. The potential valence and conduction band position of CdS and Ni-CdS thin films was found to be 9.5, 7.7 eV, and 7.2, 5.6 eV, respectively. The synthesized films were used to degrade methylene blue (MB) dye under 160W mercury vapor lamp irradiation. The degradation rate of MB dye was found to be significantly enhanced when Ni-CdS was used instead of pure CdS in visible light photocatalysis experiments. Degradation efficiency for the CdS thin films was 64% after 120 minutes, while for the Ni- CdS films, it was an impressive 84% after the same amount of time. Incorporating nickel ions into the CdS matrix improved the photocatalytic efficacy by increasing light absorption and decreasing electron-hole recombination. Films doped with Ni showed better photocatalytic activity, as the rate constant (k) for MB degradation rose from 0.028 min⁻¹ (CdS) to 0.038 min⁻¹ (Ni-CdS). Research Highlights: The hexagonal structure along the (101) crystallite orientation is revealed by the X-Ray diffraction data of the CdS and Ni-CdS thin films. Alternation in the morphology from irregularly developed nanosheets to well-developed nanosheets-like morphology with enhanced surface area for scattering and absorption of light. UV-DRS measurement of Ni-CdS thin films clearly shows a redshift, indicating a reduction in band gap energy due to nickel incorporation into CdS crystal lattices. Ni2+ incorporation into the CdS matrix which provides the new band gap position of VB and CB for the Ni-CdS thin film leads to the generation of dual ROS pathway.