Synthesis of Magnetic MnFe2O4/Polyaniline Composite Microspheres and Their Electrocatalytic Activity for Oxygen Reduction Reaction

Manganese ferrite (MnFe2O4)/polyaniline (PANI) composite microspheres were synthesized controllably by the in situ chemical polymerization of aniline in the presence of MnFe2O4 colloidal nanocrystal clusters (CNCs). MnFe2O4/PANI composites were investigated by a series of techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermal gravity (DTG). It was found that the crystalline size of MnFe2O4 nanoparticles in the composites was larger than that of primary nanoparticles in original MnFe2O4 CNCs. The thermal stability of PANI in the composites increased with the decrease of the polymer contents. Magnetic measurements showed that magnetic properties of the composites were depended on the crystalline size and the assembly of primary MnFe2O4 nanoparticles as well as the composition ratio of PANI with ferrites. The electrocatalytic activity of MnFe2O4/PANI composites and MnFe2O4 CNCs for oxygen reduction reaction was mainly relied on the crystalline size and assembly of primary nanoparticles in the samples. Based on the experimental results, the formation mechanisms of MnFe2O4/PANI composites as well as the relationship between their structures and properties have been discussed.