<p>In the present work, cobalt sulfide thin film was deposited on silicon substrate using a cheap, reproducible, and simple chemical bath deposition method. Cobalt sulfides are a relatively abundant, non-toxic raw material, it is well known for their high electrical conductivity and considerable electrochemical reaction activity. The surface morphology, crystal structure, and the optical properties of the Co_xS_y thin films were studied by scanning electron microscope, X-ray diffraction, XPS spectroscopy, Raman spectroscopy, and UV–Visible spectrophotometer. The characteristic peaks of Co-S bond were determined using FTIR spectroscopy which confirms the formation of cobalt sulfide film. The photoelectrochemical properties were determined through linear sweep voltammetry and cyclic one using 10 ⁻²&#xa0;M K₂CO₃ electrolyte in dark and under light with and without purging CO₂, respectively. According to the found results, the electrode based on cobalt sulfide/ silicon could be used as a photocathode for water oxidation and CO₂ conversion.</p> Graphical abstract <p></p>