Impact of copper-doped cobalt oxide thin films on the photocatalytic degradation of methylene blue dye under sunlight irradiation

The current study investigates the effect of copper doping with concentrations ranging from 2 wt% to 10 wt% on cobalt oxide (Co₃O₄) properties and their application in photocatalytic reactions. Undoped and copper-doped Co₃O₄ thin films were synthesized using the pyrolysis spray technique (PST) on a glass substrate at 400 °C and with 0.2 M. XRD analysis reveals that all substrates exhibited a single-phase, spinel cubic structure, indicating that incorporating copper (Cu) into the Co₃O₄ structure did not form a new crystalline phase. An increase in crystallite size was observed, rising from 25.588 to 40.940 nm. The micrograph of films was analyzed using scanning electron microscopy (SEM). UV–Vis measurements found that incorporating Cu-dopants reduced the direct band gap Eg₂ from 2.030 to 2.012. The photocatalytic efficiency of films was evaluated by measuring the degradation of methylene blue dye (MB) under sunlight irradiation for 4 h. The kinetics of MB photodegradation were evaluated using the non-linear least square method. The optimal Cu-doping concentration is at 8 wt%, with the maximum degradation of MB being 84%. It concluded that incorporating copper markedly improves the photocatalytic performance of cobalt oxide thin films.