Enhanced photocatalytic degradation property of surfactant-free cobalt oxide nanocapsules on methylene blue dye

The transition metal oxides are emerging materials in solving existing environmental problems of removal of organic dye from the industrial wastes. Out of many transition metal oxides, cobalt oxide is one such potential material of low cost, easy to synthesis, eco-friendly and easily separable from mixtures due to its magnetic property. Herein a facile surfactant-free synthesis route has been adopted for the preparation of Co 3 O 4 nanocapsules (Co 600) which exhibited a better photocatalytic degradation activity. The structure, morphology and optical behaviours were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet-visible spectroscopy (UV–vis) analyses respectively and vibration modes of Co 600 were studied using Raman analysis. The photocatalytic degradation studies of Co 600 on methylene blue (MB) were carried out under ultraviolet (UV) light irradiation. The examined results showed that the Co 600 exhibited narrow band gap of about 1.65 eV which has better photocatalytic degradation activity on MB with degradation efficiency of about 99% in 90 minute with a rate constant of about 0.064. This might be attributed due to enhanced charge separation, charge transfer and the creation of OH – and O 2 – radicals under UV irradiation. In addition, the samples were easily recovered from the dye solution using an external magnetic field.