Synthesis, Characterization and Photocatalytic Activities of Co₃O₄ - MnO₂ - ZnO Ternary Nanoparticles

Abstract

Co3O4 - MnO2 - ZnO NPs were synthesized by making use of the equimolar solutions of cobalt chloride, manganese(II) sulfate and zinc sulfate in aqueous sodium hydroxide and refluxed at elevated temperature. The synthesized mixed nano oxides were characterized by FT-IR, XRD, UV - Vis DRS, TEM, SAED, SEM, EDAX, AFM, TG/DTG and DSC. The FTIR spectra confirm the presence of M-O bonds (M = Co, Mn, Zn). The size of the Co3O4 - MnO2 - ZnO NPs are found to be 10.13 - 25.65nm through XRD studies. The XRD patterns also expose that the particle size is significantly increased with increasing concentration of the precursors. UV-Vis diffuse reflectance spectra (DRS) show that the ternary nanoparticles can be activated by UV and visible light illumination. The TEM, SEM and AFM micrographs of 0.1M Co3O4 - MnO2 - ZnO NPs show roughly spherical shape with size ranging from 10 - 30nm. EDAX analysis confirms the presence of Co, Mn, Zn and O. From TG-DTG and DSC studies, it is found that Co3O4 - MnO2 - ZnO NPs are thermally stable. The photocatalytic activity of Co3O4 - MnO2 - ZnO NPs was determined for degradation of methylene blue (MB) under sunlight. Among the samples, 0.1M Co3O4 - MnO2 - ZnO NPs exhibits the best performance (91.98%) for the degradation of MB in 90 min of irradiation time under sunlight. The factors influencing the photocatalytic activity are pH of dye solution, photocatalyst particle size, photocatalyst dosage and dye concentration.