A comparative study of single and bi-doped Co3O4 nanocatalysts for the photodegradation of methyl orange dye

In this work, pure Co3O4, Ni-, CuNi-, and CdNi-doped Co3O4 nanoparticles (NPs) were prepared via chemical co-precipitation method. The obtained Co3O4 exhibits a cubic crystalline structure with an average crystallite size of ∼19.9 nm, according to the XRD profiles. Moreover, the effects of Ni-, CuNi- and CdNi-doped Co3O4 on the crystallite size, band gap, and magnetic properties of the cubic Co3O4 were considered. It was observed that the crystallite sizes and the magnetic properties of Ni(0.1)Co3O4(0.9) and Cu(0.05)Ni(0.05)Co3O4(0.9) samples are smaller, while the optical band gaps are wider than that of pure Co3O4. The Cd(0.05)Ni(0.05)Co3O4(0.9) sample has a higher magnetic properties in comparison to the other samples. The elemental composition of the produced Co3O4, Ni-, CuNi- and CdNi-doped Co3O4 NPs is determined using the EDX technique. A morphological study by TEM showed that the CdNi-doped Co3O4 sample has semi-spherical particles with an average particle diameter of ∼70.4 nm. The photodegradation of methyl orange (MO) dye in aqueous solution under visible light irradiation was used to examine the catalytic activity of pure and doped Co3O4 NPs. The results showed that the degradation of MO dye was improved in the doped samples and takes the following order: Cd(0.05)Ni(0.05)Co3O4(0.9) (∼93%) > Cu(0.05)Ni(0.05)Co3O4(0.9) (∼85%) > Ni(0.1)Co3O4(0.9) (∼79.7%) > pure Co3O4 (∼64.4%) in 120 min of irradiation time. The pseudo-first-order reaction rate constant for Cd(0.05)Ni(0.05)Co3O4(0.9) is equal to 0.021 min−1, which is about 1.6-times increased in compared to pure Co3O4. The improved photocatalytic efficiency of this sample was attributed to an extrinsic defect generated by CdNi doping, small particle sized and high surface area, which delayed the electron/hole recombination and caused appropriate band gap configuration.